The FDA generally viewed each operating instance of Nightscout as a "medical device" subject to labeling, hazard management, and FDA reporting requirements.    Medical Data Networks LLC  asserts that its product  T1Pal  meets all of the FDA criteria for a "Class 2" medical device,  and embraces needed FDA oversight and data reporting requirements.
 Medical Data Networks LLC  is actively seeking to work more efficiently with firms that market CGM and other data so as to improve the quality and efficiency by which data is transferred into Nightscout.   Nightscout's features for remote monitoring, data integration, and sharing are of immense value to the Nightscout community and merit continued support by the CGM device manufacturers. [ citation needed ] .    T1Pal  service adds to the Nightscout software patent-pending sharing features and standard email and phone support capabilities needed to enable access the largest possible community of users.


In 2015, subsequent to the development of the Nightscout Project,  Dexcom  released a CGM system that included 'Share', providing software for transferring data to cell phones via  Bluetooth , and sharing CGM data with others via cell phone apps. [ citation needed ]


In 2017, the Spanish company Instead Technologies launched a continuous reading system named GlucoAngel for the  FreeStyle Libre flash glucose monitor . [ 15 ] [ 16 ]


In 2020,  Medical Data Networks LLC  commenced commercial service operations, providing  T1Pal  as "Nightscout in the Cloud" for $12.00/mo.
The service is supported by email and phone support for paying customers.   Beginning January 2022 the company added integrated support for  T1Pal  combined with iPhone Loop services.  This positions  Medical Data Networks LLC  as the first commercial provider of IT services needed to implement and support closed Loop operations.


The  OpenAPS  project has extended Nightscout to create a do-it-yourself "artificial pancreas", by automating basal insulin delivery by an  insulin pump  to create a "closed loop" system. [ 17 ]


Noninvasive glucose monitoring  ( NIGM ), called  Noninvasive continuous glucose monitoring  when used as a  CGM  technique, is the measurement of  blood glucose  levels, required by people with  diabetes  to prevent both chronic and acute complications from the disease, without drawing blood, puncturing the skin, or causing pain or trauma. The search for a successful technique began about 1975 and has continued to the present without a clinically or commercially viable product. [ 1 ]


As of 1999 [update] , only one such product had been approved for sale by the  FDA , based on a technique for electrically pulling glucose through intact skin, and it was withdrawn after a short time owing to poor performance and occasional damage to the skin of users. [ 2 ]


Hundreds of millions of dollars have been invested in companies who have sought the solution to this long-standing problem. Approaches that have been tried include  near-infrared spectroscopy  (NIRS, measuring glucose through the skin using light of slightly longer wavelengths than the  visible region ), [ 3 ]   transdermal  measurement (attempting to pull glucose through the skin using either chemicals, electricity or ultrasound), measuring the amount that  polarized light  is rotated by glucose in the front chamber of the eye (containing the  aqueous humor ), and many others.


A 2012 study reviewed ten technologies:  bioimpedance  spectroscopy,  microwave / RF  sensing, [ 4 ] [ 5 ]  fluorescence technology, mid-infrared spectroscopy, near-infrared spectroscopy,  optical coherence tomography , optical  polarimetry ,  Raman spectroscopy , reverse  iontophoresis , and  ultrasound  technology, concluding with the observation that none of these had produced a commercially available, clinically reliable device and that therefore, much work remained to be done. [ 6 ]


As of 2014 [update] , disregarding the severe shortcomings mentioned above, at least one non-invasive glucose meter was being marketed in a number of countries. [ 7 ] [ 8 ]  Still, as the mean absolute deviation of this device was nearly 30% in clinical trials, "further research efforts were desired to significantly improve the accuracy [...]". [ 9 ]


While multiple technologies have been tried, Raman spectroscopy has gained traction as one promising technology for measuring glucose in  interstitial fluid . Early attempts include C8 Medisensors [ 10 ]  and the Laser Biomedical Research Center at  Massachusetts Institute of Technology  (MIT) which have been working on a Raman spectroscopy sensor for more than 20 years and conducting clinical investigations in collaboration with the Clinical Research Center at  University of Missouri , Columbia, US. [ 11 ]
In 2018 a paper in PLOS ONE  showed independent validation data from a clinical investigation comprising 15 subjects with  diabetes mellitus type 1  with a mean absolute relative difference (MARD) of 25.8%. [ 12 ]  The system used, was a custom-built  confocal  Raman setup.
In 2019 researchers at the  Samsung Advanced Institute of Technology  (SAIT),  Samsung Electronics , in collaboration with the Laser Biomedical Research Center MIT developed a new approach based on Raman spectroscopy that allowed them to see the glucose signal directly. The researchers tested the system in pigs and could get accurate glucose readings for up to an hour after initial calibration. [ 13 ]


In 2020,  German Institute for Diabetes-Technology  published data from 15 subjects with type 1 diabetes on a new prototype GlucoBeam based on Raman spectroscopy from RSP Systems Denmark, showing a MARD of 23.6% on independent validation in out-patient setup with up till 8 days without recalibration. [ 14 ]


With accuracy on marketed BGM devices in the US between 5.6 and 20.8%. [ 15 ]   A NIGM solution would likely need to have an accuracy with a MARD below 20% to be widely accepted.


The number of clinical trials of non-invasive glucose monitors has grown throughout the 21st century. While the  National Institutes of Health  recorded only 4 clinical investigations of the technology from 2000 to 2015, there were 16 from 2016 to 2020. [ 16 ]


From approximately 2020, onwards there has been increased R&D activity in the space of new NIGM solutions (particularly CGM ones) with renewed focus on approaches that had already been explored, and new ones altogether.  [ 17 ]  This includes both large tech companies, such as  Apple  and  Samsung , and startup companies.


Optical spectroscopy methods in continuous glucose monitoring (CGM) utilize light to measure glucose levels in the interstitial fluid or blood. These methods typically involve shining a specific wavelength of light (near-infrared, mid-infrared, or Raman) onto the skin, where it interacts with the glucose molecules. The light either gets absorbed or scattered by the glucose, and the resulting changes in the light's properties are detected and analyzed. [ 18 ]


DiaMonTech AG is a  Berlin , Germany-based privately-held company developing the D-Pocket, [ 19 ]  a medical device that uses infrared laser technology to scan the tissue fluid in the skin and detect glucose molecules. Short pulses of infrared light are sent to the skin, which are absorbed by the glucose molecules. This generates heat waves that are detected using its patented IRE-PTD method. [ 20 ]  The company claims a high selectivity of its method, results of a first study have been published in the  Journal of Diabetes Science and Technology . In this study, a Median Absolute Relative Difference of 11.3% is claimed. [ 21 ]  DiaMonTech has announced that its envisioned follow-up product D-Sensor, will feature continuous measurements, making it a CGM though no release date has been given. [ 22 ]


Apple  has been working on a noninvasive CGM combining silicon photonics and optical absorption spectroscopy, [ 23 ]  that it seeks to integrate into its  Apple Watch . In March 2023 it was reported to have established proof-of-concept of a noninvasive CGM. [ 24 ]  Another company working on noninvasive CGM is  Masimo , which sued Apple for patent infringement in this area in 2020. [ 25 ]  Masimo has also filed new patents through its subsidiary Cercacor (pending as of September 2023) covering a joint continuous glucose monitoring and pump-closed loop delivery system. [ 26 ]


U.S. company Rockley Photonics is building a Near-Infrared system. This approach integrates Rockley’s short-wave infrared (SWIR) spectroscopy technology into its miniaturized photonic integrated circuit (PIC) chips, with the resulting mechanism aiming to be embedded into a smartwatch-style wearable device. [ 27 ]


Lithuanian  company BROLIS is another NIR Spectroscopy emerging NIGM player. [ 28 ]  Based on news reports, it developed a fully functioning prototype in 2019. [ 29 ]


Samsung  announced that it would be incorporating glucose monitoring with its smartwatch with a targeted release year of 2025. It is not clear whether the watch will integrate readings from an external CGM such as Dexcom's or Abbott's, or work standalone. [ 30 ]  The company in 2020 published literature regarding the aforementioned (see above) non-invasive method it had developed with MIT scientists to engage in continuous glucose monitoring using spectroscopy. [ 31 ]  The company has filed patents related to this technology. [ 32 ]  In January 2024, Samsung gave an update affirming its NIGM ambitions but did not give a release date. [ 33 ]


Seoul, South Korea-based start-up Apollon commenced work on a Raman CGM and secured a partnership with MIT in 2023.  [ 34 ]  In 2024, it secured 2.3B won (approximately $1.5M) in pre-Series A funding for development of needle-free glucose monitoring. [ 35 ]


Liom (formerly called  Spiden ) is a  Swiss  startup building a multi-biomarker and drug level monitoring noninvasive smartwatch wearable (using  Raman spectroscopy ) with continuous glucose monitoring capability as its first application.  [ 36 ] [ 37 ]  It has so far not attained regulatory approval as of October 2023. In January of 2024, Liom declared it had developed a prototype, with a claimed MARD (Mean Absolute Relative Difference) value to a reference glucose measurement of approximately 9%. [ 38 ]


In 2023, RSP Systems Denmark published data from prospective measurements with at least 15 days following calibration. the study was a home-based clinical study involving 160 subjects with diabetes, the largest study of its kind to date. Data from a subset of subjects with type 2 diabetes shoved 99.8% of measurements within A + B zones in the consensus error grid and a mean absolute relative difference of 14.3%. The full clinical study involved 160 subjects, 137 with type 1 on intensive insulin therapy or insulin pumps. The measurements form the type 1 diabetes subgroup, showed 96.5% of the points in zones A + B, while the typical indices of accuracy, the mean absolute relative difference (MARD) and RMSE, over the 15 days were 19.9% and 1.9 mmol/L, respectively. With 12,374 paired data points, the size of the dataset demonstrates the robustness of the Raman spectroscopy-based approach.  [ 39 ]


Electromagnetic sensing for non-invasive glucose monitoring utilizes the interaction between electromagnetic waves and the glucose molecules present in the body. These techniques typically involve applying a specific radio frequency or microwave signal to the skin, which then penetrates the underlying tissues. The presence of glucose alters the dielectric properties (permittivity and conductivity) of the tissue, leading to changes in the  amplitude , phase, or other characteristics of the transmitted or reflected  electromagnetic waves .


Electrochemical  glucose monitoring is based on the  glucose oxidation reaction .  Glucose oxidase  is the enzyme that is specific to glucose. Glucose is oxidized by oxygen in the presence of glucose oxidase and water to make  gluconolactone  and  hydrogen peroxide . Hydrogen peroxide is further oxidized at the electrode, producing free electrons, resulting in an  electrical current  proportional to the glucose concentration in an area of interest. By measuring this current, the sensor can accurately determine the glucose level. [ 40 ]


Haifa , Israel-based company HAGAR completed a study of its GWave non-invasive CGM, reporting high accuracy. This sensor uses radiofrequency waves to measure glucose levels in the blood. [ 41 ]  The device had not received regulatory approval anywhere as of August 2023. One of the criticisms of radiofrequency technology as a way of measuring glucose is that studies in 2019 found that glucose can only be detected in the far infrared (nanometer wavelengths), rather than radiofrequencies even in the centimeter and millimeter wavelength range, putting into question the viability of radio frequencies for measuring glucose. [ 42 ]  A second study (performed in Israel) reported a GWave prototype showed a MARD of 6.7% though Food and Drug Administration (FDA) comparator standards were not applied (the study determined accuracy (MARD) by comparing with a regular Abbott Blood Glucose Monitoring/fingerstick device as a comparator, which measures capillary blood glucose levels, not venous ones as required for FDA CGM approval). [ 43 ]


KnowLabs is a  Seattle , U.S-based company building a CGM called the Bio-RFID sensor, which works by sending radio waves through the skin to measure molecular signatures in the blood, which Know Labs' machine learning algorithms use to compute the user's blood sugar levels. The company reported that it had built a prototype, but had not attained regulatory approval as of August 2023. [ 44 ]  In March 2024, news outlets reported that the company's sensor had attained a MARD of 11.1%. [ 45 ]


The BioXensor developed by British company BioRX uses patented radio frequency technology, alongside a multiple sensor (also capturing blood oxygen levels,  ECG , respiration rate, heart rate and body temperature) approach. [ 46 ]  The company claims this enables the measurement of blood glucose levels every minute reliably, accurately, and non-invasively. BioXensor had not received regulatory approval as of June 2023 [update] .


Afon Technology, based in  Wales , is developing  Glucowear , a non-invasive continuous glucose monitor (CGM) using radiofrequency (RF) technology. This device, worn under a smartwatch, has the goal to monitor blood glucose in real-time. Their approach uses RF signals to detect glucose levels beneath the skin, differing from optical sensor-based methods.  [ 47 ]


Synex Medical (based in Boston, US and Toronto, Canada) uses portable  magnetic resonance spectroscopy  (MRS) for non-invasive glucose monitoring. Their compact devices aim to measure blood metabolites like glucose in real-time by analyzing the magnetic properties of hydrogen atoms in glucose molecules. [ 48 ]


Another noninvasive system was attempted to be built by US company Movano Health. It envisioned a small ring placed on the arm. Movano said in 2021 that it was building the smallest ever custom radio frequency (RF)-enabled sensor designed for simultaneous blood pressure and glucose monitoring. [ 49 ]  Movano is listed as MOVE on NASDAQ. By August 2023 Movano had shifted to building sensor rings for other parameters, such as heart rate,  blood oxygen levels, respiration rate, skin temperature variability, and menstrual symptom tracking. [ 50 ]


SugarBeat, built by  Nemaura Medical , is a wireless non-invasive blood glucose monitoring system using a disposable  skin patch . The patch connects to a rechargeable transmitter which detects blood sugar and transfers the data to a mobile app every five minutes. The patch can be used for 24 hours. Electronic currents are used to draw  interstitial fluid  to the surface to analyse the glucose level. SugarBeat has achieved regulatory approval in Saudi Arabia [ 51 ]  and Europe, [ 52 ]  though market penetration rates remain very low. The company declared  US$ 503,906 in revenue for the fiscal year ending March 2022, [ 53 ]  which compares to Dexcom's more than $3 billion. [ 54 ]   As of August 2023 [update]  it had submitted a US  FDA  premarket approval application for sugarBEAT. [ 55 ]  Nemaura was listed on  NASDAQ  since January 2018 as NMRD. [ 56 ] [ 57 ]  However, due to poor performance (a below than $35m market cap) and low trading volumes it was threatened with delisting from NASDAQ (in April 2023). [ 58 ]  It was delisted from NASDAQ January 4, 2024 and is currently trading on  OTC . [ 59 ]


Glucomodicum is based in  Helsinki , Finland and was founded as a spin out of the  University of Helsinki .  Their attempted solution uses interstitial fluid to non-invasively measure glucose levels continuously. It does not have regulatory approval. [ 60 ]  Its device is a combination of  magnetohydrodynamic  (MHD) technology, advanced algorithms and highly-sensitive biosensors which link to a smartphone app for data collection and reporting. It works by sending a small amount of energy through the skin to the interstitial fluid between the cells, bringing the fluid to the surface of the skin for non-invasive sample capture. [ 61 ]


Occuity, a  Reading , UK-based startup is taking a different approach to noninvasive glucose monitoring, by using the eye. [ 62 ]  The company states it is developing the Occuity Indigo, [ 63 ]  which aims to measure the change in refractive index of the eye to determine the concentration of glucose in the blood. [ 64 ]


BOYDSense is a French-based startup developing a noninvasive glucose monitoring device that analyzes breath-based volatile organic compounds  (VOCs) . The company’s device,  Lassie , measures specific VOCs in the breath, which are metabolic byproducts of glucose usage in the body. Early clinical trials have demonstrated that these VOCs can reliably indicate blood glucose levels in individuals with type 2 diabetes. BOYDSense’s goal is to provide a compact, affordable alternative to traditional CGMs, which rely on blood samples. The technology is currently in clinical trials, with ongoing research to refine its accuracy and algorithm.  [ 65 ]


The  overall hemostatic potential  ( OHP ) test is a  global coagulation assay  which can be used to measure  coagulation . [ 1 ] [ 2 ] [ 3 ] [ 4 ]  The OHP assay measures total  fibrin  generation in the presence of  thrombin  or  tissue factor  and  tissue plasminogen activator  (t-PA). [ 2 ] [ 1 ] [ 3 ] [ 4 ]  It generates a fibrin time curve through the use of  optical density measurement . [ 1 ]  This curve represents the balance between fibrin formation induced by thrombin or tissue factor and  fibrinolysis  induced by t-PA. [ 1 ]  The assay provides three parameters:  overall coagulation potential  ( OCP ),  overall hemostatic potential  ( OHP ), and  overall fibrinolytic potential  ( OFP ). [ 2 ] [ 1 ] [ 4 ]  OHP is the main parameter, while OCP and OFP are supplementary parameters to assess coagulation and fibrinolysis. [ 3 ]  One further parameter, clot lysis time (CLT), can also be determined. [ 3 ]  The OHP assay measures the integrated effect of  procoagulant ,  anticoagulant , and fibrinolytic factors. [ 1 ]


The OHP is a technically simple [ 1 ] [ 3 ]  but relatively labor-intensive assay. [ 2 ]  As of 2010, it had been implemented in several laboratories, but was not available commercially. [ 3 ]  The assay is novel in terms of its combined evaluation of both fibrin generation and fibrinolysis. [ 1 ]  The test is potentially useful in the evaluation of  hypercoagulability ,  hypocoagulability , and  fibrinolytic abnormalities . [ 1 ] [ 2 ] [ 3 ]  It is able to detect hypercoagulability associated with  pregnancy  and  estrogen / progestogen   hormone therapy . [ 3 ] [ 4 ]  The test has also been used to study coagulation in  feminizing hormone therapy  in  transgender women . [ 5 ]  However, more studies are needed to validate the test as a  biomarker  of  thrombosis  and other abnormalities of coagulation. [ 2 ] [ 3 ] [ 4 ]


The original OHP assay was developed in  Sweden  by Blombäck and colleagues and was first described in 1999. [ 1 ] [ 6 ] [ 7 ]  It used thrombin to trigger coagulation. [ 1 ]  Since then, a modified version has been developed which can use either thrombin or tissue factor to trigger coagulation. [ 1 ] [ 3 ] [ 8 ] [ 9 ]


Para-aminohippurate  (PAH) clearance  is a method used in  renal physiology  to measure  renal plasma flow , which is a measure of  renal function . [ citation needed ]


PAH is completely removed from blood that passes through the kidneys (PAH undergoes both glomerular filtration and tubular secretion), and therefore the rate at which the kidneys can clear PAH from the blood reflects total renal plasma flow.


The concentration of PAH is measured in one  arterial blood sample  (P PAH ) and one urine sample(U PAH ). The  urine flow  (V) is also measured. Renal perfusion flow is then calculated by:


What is calculated is the  effective renal plasma flow  (eRPF). However, since the renal  extraction ratio  of PAH almost equals 1, then eRPF almost equals RPF.


The renal  extraction ratio  of PAH in a normal individual is approximately 0.92, [ 1 ]  and thus not exactly 1.0. Thus, this method usually underestimates RPF by approximately 10%. This margin of error is generally acceptable considering the ease with which eRPF is measured. [ citation needed ]


Pentagastrin  (trade name  Peptavlon ) is a synthetic  polypeptide  that has effects like  gastrin  when given  parenterally . [ 2 ]  It stimulates the  secretion  of  gastric acid ,  pepsin , and  intrinsic factor , and has been used as a  diagnostic  aid as the  pentagastrin-stimulated calcitonin test .


Pentagastrin binds to the  cholecystokinin -B receptor, which is expressed widely in the brain.  Activation of these receptors activates the  phospholipase C  second messenger system.  When given  intravenously  it may cause  panic  attacks. [ 3 ]


Pentagastrin's  IUPAC  chemical name is "N-((1,1-dimethylethoxy)carbonyl)-beta-alanyl-L-tryptophyl-L-methionyl-L-alpha-aspartyl-L-phenylalaninamide".


Pentagastrin is also used as a stimulation test to elevate of several hormones, such as  serotonin .  It provokes flushing and is useful in evaluating patients who describe flushing, but have normal or only marginally elevated biochemical markers for  carcinoid syndrome . [ citation needed ]


It has been used to stimulate ectopic gastric mucosa for the detection of  Meckels diverticulum  by  nuclear medicine . [ citation needed ]


The  pentagastrin-stimulated calcitonin test  is a diagnostic test for  medullary carcinoma of the thyroid  (MTC). MTC is a malignancy of the  calcitonin -secreting cells of the  thyroid gland , and thus MTC is commonly associated with an elevated calcitonin level, but an elevated level may not always be obvious. The pentagastrin-stimulated calcitonin test is useful in cases of suspected MTC that are not associated with elevated calcitonin. In these patients, injecting pentagastrin will cause calcitonin levels to rise significantly above the normal or basal range. [ 4 ]  After a total  thyroidectomy  for  medullary thyroid carcinoma , the pentagastrin-stimulated  calcitonin  release can be used to detect residual  parafollicular C-cells .


Phadia  develops, manufactures and markets blood test systems to support the clinical diagnosis and monitoring of  allergy ,  asthma  and  autoimmune diseases . The company is headquartered in  Uppsala , Sweden. It has been owned by  Thermo Fisher Scientific  since 2011.


Originally part of the  Pharmacia  group of companies and an offshoot of the diagnostics division that developed out of  Pfizer  and Pharmacia & Upjohn (all Uppsala-based companies), Phadia was renamed in January 2006. [ citation needed ]


The first steps towards the present  Phadia AB  were taken in the mid 1960s. Three scientists working at  Uppsala University Hospital , Leif Wide, Rolf Axén and  Jerker Porath , then presented their ideas to use Pharmacia's separation medium  Sephadex  as the solid phase in  immunodiagnostics  tests and proposed a collaboration with the company for the commercial development. Pharmacia's management decided to go for the project and established a special R&D group for diagnostics products. In 1970 Pharmacia's first product,  Phadebas  Amylase Test, a test for the enzyme  alpha-amylase , was launched. [ citation needed ]


At the same time an important medical discovery was made which would be of decisive importance to Phadia. In 1967  immunoglobulin E , or  IgE , was discovered by two separate research teams, by Teruko and  Kimishige Ishizaka  in the US and by  Gunnar Johansson  and  Hans Bennich  [ sv ]  at Uppsala University Hospital. Johansson and Bennich worked together with Wide to develop a method to measure the levels of the substance in blood samples. Eventually a clear connection was demonstrated between  IgE  antibodies and  allergic  symptoms. Johansson, Bennich and Wide then suggested that Pharmacia should use the findings to develop a commercial allergy test. This led to the ground-breaking product Phadebas  RAST , which established the leading position that Phadia still maintains in the area of allergy testing. [ citation needed ]


Since the discovery of  IgE  in 1967, Phadia has pioneered the development of  in vitro  test systems for  allergy  ( immunoglobulin  E). These  IgE  tests have been followed by tests for  IgG  and  IgA   antibodies , as well as other analytes with applications in  asthma ,  celiac disease  and  autoimmunity . [ citation needed ]


In addition, the ImmunoCAP testing system has revolutionized the level of automation and speed which these tests are processed. Based on the high binding capacity and solid phase technology, ImmunoCAP tests are both highly sensitive and highly specific.


Phlebotomy  is the process of making a puncture in a  vein , usually in the arm, with a  cannula  for the purpose of  drawing blood . [ 1 ]  The procedure itself is known as a  venipuncture , which is also used for  intravenous therapy . A person who performs a phlebotomy is called a  phlebotomist , although most doctors, nurses, and other technicians can also carry out a phlebotomy. [ 2 ]  In contrast,  phlebectomy  is the removal of a vein.


Phlebotomies that are carried out in the treatment of some  blood disorders  are known as  therapeutic phlebotomies . [ 3 ]  The average volume of whole blood drawn in a therapeutic phlebotomy to an adult is 1 unit (450–500 ml) weekly to once every several months, as needed. [ 4 ]


From  Ancient Greek :  φλεβοτομία  ( phlebotomia  –  phleb  'blood vessel, vein' +  tomia  'cutting'), via  Old French :  flebothomie  (modern French  phlébotomie ). [ citation needed ]


Phlebotomies are carried out by phlebotomists – people trained to draw blood mostly from veins for clinical or medical testing, transfusions, donations, or research. Blood is collected primarily by performing  venipunctures , or by using  capillary blood sampling  with [ 5 ]   fingersticks  or a  heel stick  in infants for the collection of minute quantities of blood. [ 6 ]  The duties of a phlebotomist may include interpreting the tests requested, drawing blood into the correct tubes with the proper additives, accurately explaining the procedure to the person and preparing them accordingly, practicing the required forms of  asepsis , practicing standard and  universal precautions , restoring  hemostasis  of the puncture site, giving instructions on post-puncture care, affixing tubes with electronically printed labels, and delivering specimens to a laboratory. [ 7 ]  Some countries, states, or districts require that phlebotomists be licensed or registered. [ citation needed ]


A  therapeutic phlebotomy  may be carried out in the treatment of some blood disorders (example:  Hemochromatosis ,  polycythemia vera ,  porphyria cutanea tarda ), and  chronic hives  (in research). [ 8 ] [ 9 ]


In  Australia , there are a number of courses in phlebotomy offered by educational institutions, but training is typically provided on the job. The minimum primary qualification for phlebotomists in Australia is a Certificate III in Pathology Collection (HLT37215) from an approved educational institution. [ 10 ]


In the  UK  there is no requirement for holding a formal qualification or certification prior to becoming a phlebotomist as training is usually provided on the job. The  NHS  offers training with formal certification upon completion. [ 11 ]


Special state certification in the  United States  is required only in four states:  California ,  Washington ,  Nevada , and  Louisiana . A phlebotomist can become nationally certified through many different organizations. However, California currently only accepts national certificates from six agencies. These include the  American Certification Agency  (ACA),  American Medical Technologists  (AMT),  American Society for Clinical Pathology  (ASCP),  National Center for Competency Testing / Multi-skilled Medical Certification Institute  (NCCT/MMCI),  National Credentialing Agency  (NCA), and  National Healthcareer Association  (NHA). [ 12 ]  These and other agencies such as the American Society of Phlebotomy Technicians also certify phlebotomists outside the state of California. To qualify to sit for an examination, candidates must complete a full phlebotomy course and provide documentation of clinical or  laboratory  experience.


In  South Africa  learnerships to qualify as a Phlebotomy Technician are offered by many public and private educational institutions as well as by private academies owned up by pathology laboratories (such as Ampath Laboratories, Lancet, PathCare) and healthcare service providers (such as  Netcare ,  South African National Blood Service ). Some of the larger retail pharmacy chains offering in-store clinical services (such as Clicks,  Dis-Chem ) also provide training for aspirant phlebotomists. Certification can be obtained from a number of examination and testing institutions. To work as a phlebotomist in South Africa, registration with the  Health Professions Council of South Africa  (HPCSA) is required.


A phlebotomy draw station is a place where blood is drawn from patients for laboratory testing, transfusions, donations, or research purposes. The blood is typically drawn via  venipuncture  or a  finger stick  by a healthcare professional such as a  phlebotomist ,  nurse , or  medical assistant . [ 21 ]
The draw station typically includes a padded chair or a bed for patients prone to fainting during blood draws.
Draw stations can be found in various settings, such as hospitals, clinics, blood donation centers, and independent laboratories or as part of  patient service centers  (PSC).


Early phlebotomists used techniques such as  leeches  and incision to extract blood from the body. Bloodletting was used as a therapeutic as well as a prophylactic process, thought to remove toxins from the body and to balance the  humors . While physicians did perform bloodletting, it was a specialty of  barber surgeons , the primary provider of health care to most people in the medieval and early modern eras.


Plasma osmolality  measures the body's  electrolyte–water balance . [ 1 ]  There are several methods for arriving at this quantity through measurement or calculation.


Osmolality  and  osmolarity  are measures that are technically different, but functionally the same for normal use. Whereas osmolality (with an "l") is defined as the number of  osmoles  (Osm) of solute per  kilogram  of  solvent  (osmol/kg or Osm/kg), osmolarity (with an "r") is defined as the number of osmoles of solute per  liter  (L) of  solution  (osmol/L or Osm/L). As such, larger numbers indicate a greater concentration of solutes in the plasma.


Osmolality can be measured on an analytical instrument called an  osmometer . It works on the method of depression of  freezing point . [ citation needed ]


Osmolarity is affected by changes in water content, as well as temperature and pressure. In contrast, osmolality is independent of temperature and pressure. For a given solution,  osmolarity  is slightly less than osmolality, because the total solvent weight (the  divisor  used for osmolality) excludes the weight of any solutes, whereas the total solution volume (used for osmolarity) includes solute content. Otherwise, one litre of plasma would be equivalent to one kilogram of plasma, and plasma osmolarity and plasma osmolality would be equal. However, at low concentrations (below about 500 mM), the mass of the solute is negligible compared to the mass of the solvent, and osmolarity and osmolality are very similar. [ citation needed ]


Technically, the terms can be compared as follows: [ 2 ]


Therefore, bedside calculations are actually in units of  osmolarity , whereas laboratory measurements will provide readings in units of  osmolality . In practice, there is almost negligible difference between the absolute values of the different measurements.  For this reason, both terms are often used interchangeably, even though they refer to different units of measurement.


Normal human  reference range  of osmolality in plasma is about 275-299 milli-osmoles per kilogram. [ 3 ]


Plasma osmolarity of some reptiles, especial those from a freshwater aquatic environment, may be lower than that of mammals (e.g.  < 260 mOsm/L) during favourable conditions. Consequently, solutions osmotically balanced for mammals (e.g., 0.9% normal saline) are likely to be mildly  hypertonic  for such animals.
Many arid species of reptiles and hibernating  uricotelic  species allow major elevations of plasma osmolarity (e.g.  > 400 mOsm/L) that could be fatal to some mammals. [ citation needed ]


Deep-sea fish have adapted to the extreme hydrostatic pressures of depth through a number of factors, including increasing osmolality, with one of the deepest known fish in the world, the hadal snailfish ( Notoliparis kermadecensis)  having a recorded muscle osmolality of 991 ± 22 mOsmol/kg, almost four times the osmolality of mammals and three times that of shallow water fish species (typically 350 mOsmol/kg). [ 4 ]


As  cell membranes  in general are freely permeable to water, the osmolality of the  extracellular fluid  (ECF) is approximately equal to that of the  intracellular fluid  (ICF). Therefore, plasma osmolality is a guide to intracellular osmolality. This is important, as it shows that changes in ECF osmolality have a great effect on ICF osmolality — changes that can cause problems with normal cell functioning and volume. If the ECF were to become too  hypotonic , water would readily fill surrounding cells, increasing their volume and potentially  lysing  them ( cytolysis ). Many poisons, medications and diseases affect the balance between the ICF and ECF, affecting individual cells and homeostasis as a whole. [ 5 ]


Osmolality of  blood  increases with  dehydration  and decreases with overhydration. In normal people, increased osmolality in the blood will stimulate secretion of  antidiuretic hormone  (ADH). This will result in increased water reabsorption, more concentrated  urine , and less concentrated blood plasma. A low serum osmolality will suppress the release of ADH, resulting in decreased water reabsorption and more concentrated plasma.


Syndrome of inappropriate ADH secretion  occurs when excessive release of antidiuretic hormone results in inappropriately elevated urine osmolality (>100 mOsmol/L) relative to the blood plasma, leading to  hyponatraemia . This ADH secretion may occur in excessive amounts from the  posterior pituitary gland , or from ectopic sources such as  small-cell carcinoma of the lung . [ 6 ]


Elevation may be associated with stroke mortality. [ 7 ]


In medical lab reports, this quantity often appears as "Osmo, Calc" or "Osmo (Calc)." According to the international SI unit use the following equation :


Calculated osmolarity = 2 Na + Glucose + Urea (all in mmol/L)


As Na+ is the major extracellular cation, the sum of osmolarity of all other anions can be assumed to be equal to natremia, hence [Na+]x2 ≈ [Na+] + [anions]


To calculate plasma osmolality use the following equation (typical in the US):


If the patient has ingested  ethanol , the ethanol level should be included in the calculated osmolarity:


Based on the molecular weight of ethanol the divisor should be 4.6 but empiric data shows that ethanol does not behave as an ideal osmole.


The  osmolar gap  is the difference between the measured osmolality and the calculated osmolarity.  The difference in units is attributed to the difference in the way that blood solutes are measured in the laboratory versus the way they are calculated.  The laboratory value measures the freezing point depression, properly called  osmolality  while the calculated value is given in units of  osmolarity .  Even though these values are presented in different units, when there is a small amount of solute compared to total volume of solution, the absolute values of osmolality vs. osmolarity are very close.  Often, this results in confusion as to which units are meant.  For practical purposes, the units are considered interchangeable.  The resulting "osmolar gap" can be thought of as either osmolar or osmolal, since both units have been used in its derivation. [ citation needed ]


Measured osmolality is abbreviated "MO", calculated osmolarity is abbreviated "CO", and the osmolality gap is abbreviated "OG". [ 9 ]


Clinically, the osmolar gap is used to detect the presence of an osmotically active particle that is not normally found in plasma, usually a toxic alcohol such as ethanol, methanol or isopropyl alcohol.


Platelet swirling  is a  noninvasive  method for testing the quality of  platelet-rich plasma  (PRP). [ 1 ]   Platelet swirling is caused by  light diffraction  due to the alignment of normal disc-shaped  platelets . These discs align light that is diffracted, creating a cloud- or swirl-like appearance. [ citation needed ]


Results of a platelet swirling test are recorded as positive or extensive swirl, moderate or intermediate swirl, and absent or negative swirl. [ citation needed ]


A  Price-Jones curve  is a graph showing the  distribution  of diameters of  red blood cells . Higher diameter may be seen in  pernicious anaemia , while lower diameter may be seen after  haemorrhage .


A Price-Jones curve can be used in the diagnosis of  anaemia . [ 1 ] [ 2 ]  Price-Jones curves usually vary both by average red blood cell size, and the distribution of sizes. [ 3 ]


Higher red blood cell diameter and wider variation in size are often seen in  pernicious anaemia . [ 3 ]  Lower diameter with normal variation in size are often seen after  haemorrhage . [ 3 ]  A higher variation in size is known as  anisocytosis . [ 4 ] [ 5 ]


A  blood smear  can be used to view individual  red blood cells . The diameter of each red blood cell can be measured, which is usually analogous to volume. [ 2 ]  This is usually performed automatically by particle counters. [ 2 ] [ 4 ]  Data is then converted into a  histogram . [ 1 ]  This can be used to assess  red blood cell distribution width  (RDW). [ 1 ] [ 4 ]


Cecil Price-Jones first proposed using the Price-Jones curve in a 1922 paper. [ 6 ]  It has been used for assessing  red blood cells  since then. [ 7 ]


Procalcitonin  ( PCT ) is a  peptide  precursor of the hormone  calcitonin , the latter being involved with  calcium   homeostasis . It arises once preprocalcitonin is cleaved by  endopeptidase . [ 1 ]  It was first identified by Leonard J. Deftos and Bernard A. Roos in the 1970s. [ 2 ]  It is composed of 116  amino acids  and is produced by  parafollicular cells  (C cells) of the  thyroid  and by the  neuroendocrine cells  of the lung and the intestine.


The level of procalcitonin in the blood stream of healthy individuals is below the limit of detection (0.01 μg/L) of clinical assays. [ 3 ]  The level of procalcitonin rises in a response to a pro-inflammatory stimulus, especially of  bacterial  origin. It is therefore often classed as an  acute phase reactant . [ 4 ]  The induction period for procalcitonin ranges from 4–12 hours with a half-life spanning anywhere from 22–35 hours. [ 5 ]  It does not rise significantly with viral or non-infectious inflammations. In the case of viral infections this is due to the fact that one of the cellular responses to a viral infection is to produce  interferon gamma , which also inhibits the initial formation of procalcitonin. [ 6 ]  With the inflammatory cascade and systemic response that a severe  infection  brings, the blood levels of procalcitonin may rise multiple orders of magnitude with higher values correlating with more severe disease. [ 7 ]  However, the high procalcitonin levels produced during infections are not followed by a parallel increase in calcitonin or a decrease in serum calcium levels. [ 8 ]


PCT is a member of the  calcitonin  (CT) superfamily of  peptides . It is a peptide of 116 amino acids with an approximate molecular weight of 14.5 kDa, and its structure can be divided into three sections ( see Figure 1 ): [ 9 ]  amino terminus (represented by the ball and stick model in Figure 1), immature calcitonin (shown in Figure 1 from PDB as the crystal structure of procalcitonin is not yet available), and calcitonin carboxyl-terminus peptide 1. [ 9 ]  Under normal physiological conditions, active CT is produced and secreted in the C-cells of the  thyroid gland  after proteolytic cleavage of PCT, meaning, in a healthy individual, that PCT levels in circulation are very low (<.05 ng/mL). [ citation needed ]  The pathway for production of PCT under normal and inflammatory conditions are shown in Figure 2. [ 10 ]  During inflammation, LPS, microbial toxin, and inflammatory mediators, such as IL-6 or TNF-α, induce the CALC-1 gene in adipocytes, but PCT never gets cleaved to produce CT. [ 10 ]  In a healthy individual, PCT in endocrine cells is produced by CALC-1 by elevated calcium levels, glucocorticoids, CGRP, glucagon, or gastrin, and is cleaved to form CT, which is released to the blood. [ 10 ]


PCT is located on the CALC-1 gene on  chromosome  11. [ 9 ]  Bacterial infections induce a universal increase in the CALC-1 gene expression and a release of PCT (>1 μg/mL). [ 11 ]  Expression of this hormone occurs in a site specific manner. [ 9 ]  In healthy and non-infected individuals, transcription of PCT only occurs in  neuroendocrine  tissue, except for the C cells in the thyroid. The formed PCT then undergoes post-translational modifications, resulting in the production small peptides and mature CT by removal of the C-terminal glycine from the immature CT by peptidylglycine α-amidating monooxygenase (PAM). [ 12 ]  In a microbial infected individual, non-neuroendocrine tissue also secretes PCT by expression of CALC-1. A microbial infection induces a substantial increase in the expression of CALC-1, leading to the production of PCT in all differentiated cell types. [ 13 ]  The function of PCT synthesized in nonneuroendocrine tissue due to a microbial infection is currently unknown, but, its detection aids in the differentiation of inflammatory processes. [ 9 ]


Due to PCT’s variance between microbial infections and healthy individuals, it has become a marker to improve identification of bacterial infection and guide antibiotic therapy. [ 14 ]  The table below is a summary from Schuetz, Albrich, and Mueller, [ 14 ]  summarizing the current data of selected, relevant studies investigating PCT in different types of infections.


Legend:
✓ = Moderate evidence in favor of PCT
✓✓ = Good evidence in favor of PCT
✓✓✓ = Strong evidence in favor of PCT
~ = Evidence in favor or against the use of PCT, or still undefined


Measurement of procalcitonin can be used as a marker of severe  sepsis  caused by bacteria and generally grades well with the degree of sepsis, [ 51 ]  although levels of procalcitonin in the  blood  are very low. PCT has the greatest  sensitivity  (90%) and  specificity  (91%) for differentiating patients with  systemic inflammatory response syndrome  (SIRS) from those with sepsis, when compared with  IL-2 ,  IL-6 ,  IL-8 ,  CRP  and  TNF-alpha . [ 52 ]  Evidence is emerging that procalcitonin levels can reduce unnecessary antibiotic prescribing to people with  lower respiratory tract infections . [ 53 ]  Currently, procalcitonin assays are widely used in the clinical environment. [ 54 ]


A meta-analysis reported a  sensitivity  of 76% and  specificity  of 70% for bacteremia. [ 55 ]


A 2018 systematic review comparing PCT and  C-reactive protein (CRP)  found PCT to have a sensitivity of 80% and a specificity of 77% in identifying septic patients.  In the study, PCT outperformed CRP in diagnostic accuracy of predicting sepsis. [ 56 ]


In a 2018 meta-analysis of randomized trials of over 4400 ICU patients with sepsis, researchers concluded that PCT led therapy resulted in lower mortality and lower antibiotic administration. [ 57 ]


Immune responses to both  organ rejection  and severe bacterial infection can lead to similar symptoms such as swelling and fever that can make initial diagnosis difficult. To differentiate between acute rejection of an organ transplant and bacterial infections, plasma procalcitonin levels have been proposed as a potential diagnostic tool. [ 58 ]  Typically the levels of procalcitonin in the blood remain below 0.5 ng/mL in cases of acute organ rejection, which has been stated previously to be well below the 1 μg/mL typically seen in bacterial infection. [ 6 ]


Given procalcitonin is a blood marker for bacterial infections, evidence shows that it is a useful tool in guiding the initiation and duration of  antibiotics  in patients with  bacterial pneumonia  and other acute respiratory infections. [ 59 ]  The use of procalcitonin guided antibiotic therapy leads to lower mortality, less antibiotic usage, decreased side effects due to antibiotics and promotes good  antibiotic stewardship . [ 59 ]   The value in these protocols are evident since a high PCT level correlates with increased mortality in critically ill pneumonia patients especially those with a low  CURB-65 pneumonia risk factor  score. [ 60 ]


In adults with acute respiratory infections, a 2017 systematic review found that PCT-guided therapy reduced mortality, reduced antibiotic use (2.4 fewer days of antibiotics) and led to decreased  adverse drug effects  across a variety of clinical settings (ED, ICU, primary care clinic). [ 59 ]


Procalcitonin-guided treatment limits antibiotic exposure with no increased mortality in patients with acute exacerbation of  chronic obstructive pulmonary disease . [ 61 ]


Using procalcitonin to guide protocol in  acute asthma exacerbation  led to reduction in prescriptions of antibiotics in primary care clinics, emergency departments and during hospital admission.  This was apparent without an increase in ventilator days or risk of intubation.  Be that acute  asthma  exacerbation is one condition that leads to overuse of antibiotics worldwide, researchers concluded that PCT could help curb over-prescribing. [ 62 ]


PCT serves a marker to help differentiate acute respiratory illness such as infection from an acute cardiovascular concern.  It also has value as a prognostic lab value in patients with  atherosclerosis  or  coronary heart disease  as its levels correlate with the severity of the illness. [ 63 ]


The  European Society of Cardiology  recently released a PCT-guided algorithm for administering antibiotics in patients with  dyspnea  and suspected acute  heart failure . The guidelines use a cut off point of     .2 ng/mL and above as the point at which to give antibiotics. [ 64 ]   This coincides with a 2017 review of literature which concluded that PCT can help reduce antibiotic overuse in patients presenting with acute heart failure. [ 65 ]   In regards to mortality, a meta analysis of over 5000 patients with heart failure concluded that elevated PCT was reliable in predicting short term mortality. [ 66 ]


Blood procalcitonin levels can help confirm  bacterial meningitis  and. if negative, can effectively rule out bacterial meningitis.  This was shown in a review of over 2000 patients in which PCT had a sensitivity of 86% and a specificity of 80% for  cerebrospinal fluid  PCT.  Blood PCT measurements proved superior to cerebrospinal fluid PCT with a sensitivity of 95% and a specificity of 97% as a marker for bacterial meningitis. [ 67 ]


In acute meningitis, serum PCT is useful as a biomarker for sepsis.  It can also be of use in determining viral meningitis versus bacterial meningitis. These findings are the result of a 2018 literature review. [ 68 ]   This followed a 2015 meta analysis that showed that PCT had a sensitivity of 90% and a specificity of 98% in judging viral versus bacterial meningitis.  PCT also outperformed other biomarkers such as C-reactive protein. [ 69 ]


Evidence shows that an elevated PCT above .5 ng/mL could help diagnose infectious complications of  inflammatory bowel disease  such as abdominal abscesses, bacterial  enterocolitis  etc.  PCT can be effective in early recognition of infections in IBD patients and decisions on whether to prescribe antibiotics. [ 70 ]


Patients with chronic kidney disease and end-stage renal disease are at higher risk for infections, and procalcitonin has been studied in these populations, who often have higher levels. Procalcitonin can be dialyzed, and so levels are dependent upon when patients receive  hemodialysis . While there is no formally accepted cutoff value for patients undergoing HD, using a value of greater or equal to 0.5 ng/mL yielded a sensitivity of 97-98% and a specificity of 70-96%. [ 71 ]


PCT, possibly together with  CRP , is used to corroborate the  MELD  score. [ 72 ] [ 73 ]


PCT at a cutoff  value of .5 ng/mL was effective at ruling in  septic arthritis  in an analysis of over 8000 patients across 10 prospective studies.  PCT had a sensitivity of 54% and specificity of 95%.  The study also concluded that PCT outperforms  C-reactive protein  in differentiating septic arthritis from non-septic arthritis. [ 74 ]


A 2016 literature review showed that PCT has good value in diagnosing infections in oncologic patients. Moreso, it is especially effective in diagnosing major life threatening episodes in cancer patient such as bacteremia and sepsis. [ 75 ]  Procalcitonin is reliable to monitor recurrence of  medullary thyroid carcinoma .  In detecting cancer recurrence, PCT had a sensitivity and specificity of 96% and 96% respectively. [ 76 ]


In a meta analysis of 17 studies, PCT had a sensitivity of 85% and a specificity of 54% in diagnosing sepsis in neonates and children.  The PCT cut off used was between 2-2.5 ng/mL. [ 77 ]


In children presenting with fever without an apparent source, a PCT level of .5 ng/mL had a sensitivity of 82% and specificity of 86%.  At a 5 ng/mL value, the sensitivity and specificity were 61% and 94%.  PCT can help the clinical decision making while identifying invasive bacterial infection in children with unexplained fever. [ 78 ]


PCT levels correlate with the degree of illness in pediatric patients with sepsis or  urinary tract infections  making it effective as a prognostic lab value in these patients. [ 79 ]


Procalcitonin guided cessation of antibiotic use reduces duration of  antibiotic  exposure and lowers mortality in critically ill patients in the  Intensive Care Unit . [ 80 ]


In adult emergency department patients with respiratory tract illnesses,  PCT-guided treatment groups had reduced antibiotic use. [ 81 ]  PCT references ranges are also used to determine the likelihood a patient has systemic infection (sepsis), thereby reducing incidence of unnecessary antibiotic use in cases where sepsis is unlikely. [ 82 ]


Although some literature differs in antibiotic cessation requirements the general consensus is stopping antibiotics when procalcitonin levels fall 80% below peak or below 0.5 μg/L at day five or later during antibiotic therapy. [ 83 ]


Excessive overdose on  amphetamine  or  its analogs  can induce systemic inflammation; in a case report of amphetamine overdose, without bacterial infection, significant elevations in procalcitonin were observed. [ 84 ]


2ZCH ,  2ZCK ,  2ZCL ,  3QUM


NP_001025218 NP_001025219 NP_001639


Prostate-specific antigen  ( PSA ), also known as  gamma-seminoprotein  or  kallikrein-3  ( KLK3 ), P-30 antigen, is a  glycoprotein   enzyme  encoded in humans by the  KLK3   gene . PSA is a member of the  kallikrein -related  peptidase  family and is secreted by the  epithelial cells  of the  prostate  gland in men and the  paraurethral glands  in women. [ 5 ]


PSA is produced for the  ejaculate , where it liquefies  semen  in the seminal coagulum and allows  sperm  to swim freely. [ 6 ]  It is also believed to be instrumental in dissolving  cervical mucus , allowing the entry of sperm into the  uterus . [ 7 ]


PSA is present in small quantities in the  serum  of men with healthy prostates, but is often elevated in the presence of  prostate cancer  or other prostate disorders. [ 8 ]  PSA is not uniquely an indicator of prostate cancer, but may also detect  prostatitis  or  benign prostatic hyperplasia . [ 9 ]


Clinical practice guidelines  for prostate cancer  screening  vary and are controversial, in part due to uncertainty as to whether the benefits of screening ultimately outweigh the risks of  overdiagnosis  and overtreatment. [ 10 ]  In the United States, the  Food and Drug Administration  (FDA) has approved the PSA test for annual screening of prostate cancer in men of age 50 and older. [ medical citation needed ]  The patient is required to be informed of the risks and benefits of PSA testing prior to performing the test. [ medical citation needed ]


In the United Kingdom, the  National Health Service  (NHS) as of 2018 [update]  does not mandate, nor advise for PSA test, but allows patients to decide based on their doctor's advice. [ 11 ]  The NHS does not offer general PSA screening, for similar reasons. [ 12 ]


PSA levels between 4 and 10   ng/mL (nanograms per milliliter) are considered to be suspicious, and consideration should be given to confirming the abnormal PSA with a repeat test. If indicated,  prostate biopsy  is performed to obtain a tissue sample for histopathological analysis.  [ citation needed ]


While PSA testing may help 1 in 1,000 avoid death due to prostate cancer, 4 to 5 in 1,000 would die from prostate cancer after 10 years even with screening. This means that PSA screening may reduce mortality from prostate cancer by up to 25%. Expected harms include anxiety for 100–120 receiving false positives, biopsy pain, and other complications from biopsy for false positive tests. [ medical citation needed ]


Use of PSA screening tests is also controversial due to questionable test accuracy. The screening can present abnormal results even when a man does not have cancer (known as a  false-positive  result ), or normal results even when a man does have cancer (known as a  false-negative  result ). [ 13 ]  False-positive test results can cause confusion and anxiety in men, and can lead to unnecessary prostate  biopsies , a procedure which causes risk of pain, infection, and  hemorrhage . False-negative results can give men a false sense of security, though they may actually have cancer. [ medical citation needed ]


Of those found to have prostate cancer, overtreatment is common because most cases of prostate cancer are not expected to cause any symptoms due to low rate of growth of the prostate tumor. Therefore, many will experience the side effects of treatment, such as for every 1000 men screened, 29 will experience erectile dysfunction, 18 will develop urinary incontinence, two  will have serious cardiovascular events, one will develop pulmonary embolus or deep venous thrombosis, and one perioperative death. [ failed verification ]  Since the expected harms relative to risk of death are perceived by patients as minimal, men found to have prostate cancer usually (up to 90% of cases) elect to receive treatment. [ 14 ] [ 15 ] [ 16 ]


Men with prostate cancer may be characterized as low, intermediate, or high risk for having/developing metastatic disease or dying of prostate cancer. PSA level is one of three variables on which the risk stratification is based; the others are the grade of prostate cancer ( Gleason grading system ) and the stage of cancer based on physical examination and imaging studies. D'Amico criteria for each risk category are: [ 17 ]


Given the relative simplicity of the 1998 D'Amico criteria (above), other predictive models of risk stratification based on  mathematical probability  constructs exist or have been proposed to allow for better matching of treatment decisions with disease features. [ 18 ]
Studies are being conducted into the incorporation of multiparametric  MRI  imaging results into  nomograms  that rely on PSA, Gleason grade, and tumor stage. [ 19 ]


PSA levels are monitored periodically (e.g., every 6–36 months) after treatment for prostate cancer – more frequently in patients with high-risk disease, less frequently in patients with lower-risk disease. If surgical therapy (i.e., radical prostatectomy) is successful at removing all prostate tissue (and prostate cancer), PSA becomes undetectable within a few weeks. A subsequent rise in PSA level above 0.2   ng/mL [ 20 ]  L [ disputed  –  discuss ]  is generally regarded as evidence of recurrent prostate cancer after a radical prostatectomy; less commonly, it may simply indicate residual benign prostate tissue. [ citation needed ]


Following radiation therapy of any type for prostate cancer, some PSA levels might be detected, even when the treatment ultimately proves to be successful. This makes  interpreting the relationship between PSA levels and recurrence/persistence of prostate cancer after radiation therapy more difficult. PSA levels may continue to decrease for several years after radiation therapy. The lowest level is referred to as the PSA nadir. A subsequent increase in PSA levels by 2.0   ng/mL [ disputed  –  discuss ]  above the nadir is the currently accepted definition of prostate cancer recurrence after radiation therapy. [ citation needed ]


Recurrent prostate cancer detected by a rise in PSA levels after curative treatment is referred to as a " biochemical recurrence ". The likelihood of developing recurrent prostate cancer after curative treatment is related to the pre-operative variables described in the preceding section (PSA level and grade/stage of cancer). Low-risk cancers are the least likely to recur, but they are also the least likely to have required treatment in the first place. [ citation needed ]


PSA levels increase in the setting of prostate infection/inflammation (prostatitis), often markedly (> 100).


PSA was first identified by researchers attempting to find a substance in seminal fluid that would aid in the investigation of rape cases. [ 21 ]  PSA is used to indicate the presence of  semen  in forensic  serology . [ 22 ]  The semen of adult males has PSA levels far in excess of those found in other tissues; therefore, a high level of PSA found in a sample is an indicator that semen may be present. Because PSA is a  biomarker  that is expressed independently of  spermatozoa , it remains useful in identifying semen from  vasectomized  and  azoospermic  males. [ 23 ]


PSA can also be found at low levels in other body fluids, such as urine and breast milk, thus setting a high minimum threshold of interpretation to rule out  false positive  results and conclusively state that semen is present. [ 24 ]  While traditional tests such as crossover  electrophoresis  have a sufficiently low sensitivity to detect only seminal PSA, newer diagnostics tests developed from clinical  prostate cancer screening  methods have lowered the threshold of detection down to 4   ng/mL. [ 25 ]  This level of antigen has been shown to be present in the peripheral blood of males with prostate cancer, and rarely in female urine samples and breast milk. [ 24 ]


PSA is produced in the  epithelial  cells of the prostate, and can be demonstrated in biopsy samples or other  histological  specimens using  immunohistochemistry . Disruption of this epithelium, for example in inflammation or  benign prostatic hyperplasia , may lead to some diffusion of the antigen into the tissue around the epithelium, and is the cause of elevated blood levels of PSA in these conditions. [ 26 ]


More significantly, PSA remains present in prostate cells after they become malignant. Prostate cancer cells generally have variable or weak staining for PSA, due to the disruption of their normal functioning. Thus, individual prostate cancer cells produce less PSA than healthy cells; the raised serum levels in prostate cancer patients is due to the greatly increased number of such cells, not their individual activity. In most cases of prostate cancer, though, the cells remain positive for the antigen, which can then be used to identify  metastasis . Since some high-grade prostate cancers may be entirely negative for PSA, however, histological analysis to identify such cases usually uses PSA in combination with other antibodies, such as  prostatic acid phosphatase  and  CD57 . [ 26 ]


The physiological function of KLK3 is the dissolution of the coagulum, the sperm-entrapping gel composed of  semenogelins  and  fibronectin . Its proteolytic action is effective in liquefying the coagulum so that the sperm can be liberated. The activity of PSA is well regulated. In the prostate, it is present as an inactive pro-form, which is activated through the action of  KLK2 , another kallikrein-related peptidase. In the prostate, zinc ion concentrations are 10 times higher than in other bodily fluids. Zinc ions have a strong inhibitory effect on the activity of PSA and on that of KLK2, so that PSA is totally inactive. [ 27 ]


Further regulation is achieved through pH variations. Although its activity is increased by higher pH, the inhibitory effect of zinc also increases. The pH of semen is slightly alkaline and the concentrations of zinc are high. On ejaculation, semen is exposed to the acidic pH of the  vagina , due to the presence of  lactic acid . In fertile couples, the final vaginal pH after coitus approaches the 6-7 levels, which coincides well with reduced zinc inhibition of PSA. At these pH levels, the reduced PSA activity is countered by a decrease in zinc inhibition. Thus, the coagulum is slowly liquefied, releasing the sperm in a well-regulated manner. [ citation needed ]


Prostate-specific antigen (PSA, also known as kallikrein III, seminin, semenogelase, γ-seminoprotein and P-30 antigen) is a 34- kD   glycoprotein  produced almost exclusively by the  prostate gland . It is a  serine protease  ( EC   3.4.21.77 )  enzyme , the  gene  of which is located on the 19th  chromosome  (19q13) in humans. [ 28 ]


The discovery of prostate-specific antigen (PSA) is beset with controversy; as PSA is present in prostatic tissue and semen, it was independently discovered and given different names, thus adding to the controversy. [ 29 ]


Flocks was the first to experiment with antigens in the prostate [ 30 ]  and 10 years later  Ablin  reported the presence of precipitation antigens in the prostate. [ 31 ]


In 1971, Mitsuwo Hara characterized a unique protein in the semen fluid, gamma-seminoprotein. Li and Beling, in 1973, isolated a protein, E1, from human semen in an attempt to find a novel method to achieve fertility control. [ 32 ] [ 33 ]


In 1978, Sensabaugh identified semen-specific protein p30, but proved that it was similar to E1 protein, and that prostate was the source. [ 34 ]  In 1979, Wang purified a tissue-specific antigen from the prostate ('prostate antigen'). [ 35 ]


PSA was first measured quantitatively in the blood by Papsidero in 1980, [ 36 ]  and Stamey carried out the initial work on the clinical use of PSA as a marker of prostate cancer. [ 29 ]


PSA is normally present in the  blood  at very low levels. The  reference range  of less than 4   ng/mL for the first commercial PSA test, the Hybritech Tandem-R PSA test released in February 1986, was based on a study that found 99% of 472 apparently healthy men had a total PSA level below 4   ng/mL. [ 37 ] [ 38 ] [ 39 ] [ 40 ] [ 41 ] [ 42 ] [ 43 ] [ 44 ]


Increased levels of PSA may suggest the presence of prostate cancer. However, prostate cancer can also be present in the complete absence of an elevated PSA level, in which case the test result would be a  false negative . [ 45 ]


Obesity  has been reported to reduce serum PSA levels. [ 46 ]  Delayed early detection may partially explain worse outcomes in obese men with early prostate cancer. [ 47 ]  After treatment, higher BMI also correlates to higher risk of recurrence. [ 48 ]


PSA levels can be also increased by  prostatitis , irritation,  benign prostatic hyperplasia  (BPH), and recent ejaculation, [ 49 ] [ 50 ]  producing a  false positive  result. Digital  rectal examination  (DRE) has been shown in several studies [ 51 ] [ 52 ] [ 53 ] [ 54 ]  to produce an increase in PSA. However, the effect is clinically insignificant, since DRE causes the most substantial increases in patients with PSA levels already elevated over 4.0   ng/mL. PSA levels are higher during the summer than during the rest of the year. [ 55 ] [ 56 ]


The "normal"  reference ranges  for prostate-specific antigen increase with age, as do the usual ranges in cancer (per associated table). [ 57 ] [ 58 ]


Despite earlier findings, [ 59 ]  recent research suggests that the rate of increase of PSA (e.g. >0.35   ng/mL/yr, the 'PSA velocity' [ 60 ] ) is not a more specific marker for prostate cancer than the serum level of PSA. [ 61 ]


However, the PSA rate of rise may have value in prostate cancer prognosis. Men with prostate cancer whose PSA level increased by more than 2.0   ng per milliliter during the year before the diagnosis of prostate cancer have a higher risk of death from prostate cancer despite undergoing  radical prostatectomy . [ 62 ]  PSA velocity (PSAV) was found in a 2008 study to be more useful than the PSA doubling time (PSA DT) to help identify those men with life-threatening disease before start of treatment. [ 63 ]


Men who are known to be at risk for prostate cancer, and who decide to plot their PSA values as a function of time (i.e., years), may choose to use a  semi-log plot . An exponential growth in PSA values appears as a straight line [ 64 ]  on a semi-log plot, so that a new PSA value significantly above the straight line signals a  switch  to a new and significantly higher growth rate, [ 64 ]  i.e., a higher PSA velocity.


Most PSA in the blood is bound to serum proteins. A small amount is not protein-bound and is called 'free PSA'. In men with prostate cancer, the ratio of free (unbound) PSA to total PSA is decreased. The risk of cancer increases if the free to total ratio is less than 25%. (See graph) The lower the ratio is, the greater the probability of prostate cancer. Measuring the ratio of free to total PSA appears to be particularly promising for eliminating unnecessary  biopsies  in men with PSA levels between 4 and 10   ng/mL. [ 66 ]  However, both total and free PSA increase immediately after ejaculation, returning slowly to baseline levels within 24 hours. [ 49 ]


The PSA test in 1994 failed to differentiate between prostate cancer and benign prostate hyperplasia (BPH) and the commercial assay kits for PSA did not provide correct PSA values. [ 67 ]  Thus with the introduction of the ratio of free-to-total PSA, the reliability of the test has improved. Measuring the activity of the enzyme could add to the ratio of free-to-total PSA and further improve the diagnostic value of test. [ 68 ]  Proteolytically active PSA has been shown to have an anti-angiogenic effect  [ 69 ]  and certain inactive subforms may be associated with prostate cancer, as shown by MAb 5D3D11, an antibody able to detect forms abundantly represented in sera from cancer patients. [ 70 ]
The presence of inactive proenzyme forms of PSA is another potential indicator of disease. [ 71 ]


PSA exists in serum in the free (unbound) form and in a complex with  alpha 1-antichymotrypsin ; research has been conducted to see if measurements of complexed PSA are more specific and sensitive biomarkers for prostate cancer than other approaches. [ 72 ] [ 73 ]


The term prostate-specific antigen is a  misnomer : it is an  antigen  but is not specific to the prostate. Although present in large amounts in prostatic tissue and semen, it has been detected in other body fluids and tissues. [ 24 ]


In women, PSA is found in  female ejaculate  at concentrations roughly equal to that found in male semen. [ 5 ]  Other than semen and female ejaculate, the greatest concentrations of PSA in biological fluids are detected in breast milk and amniotic fluid. Low concentrations of PSA have been identified in the urethral glands, endometrium, normal breast tissue and salivary gland tissue. PSA also is found in the serum of women with breast, lung, or uterine cancer and in some patients with renal cancer. [ 74 ]


Tissue samples can be stained for the presence of PSA in order to determine the origin of malignant cells that have metastasized. [ 75 ]


Prostate-specific antigen has been shown to  interact  with  protein C inhibitor . [ 76 ] [ 77 ]
Prostate-specific antigen interacts with and activates the vascular endothelial growth factors  VEGF-C  and  VEGF-D , which are involved in tumor  angiogenesis  and in the lymphatic  metastasis  of tumors. [ 78 ]


Prothrombin fragment 1+2  ( F1+2 ), also written as  prothrombin fragment 1.2  ( F1.2 ), is a  polypeptide  fragment of  prothrombin  (factor II) generated by the  in vivo   cleavage  of prothrombin into  thrombin  (factor IIa) by the  enzyme   prothrombinase  (a complex of  factor Xa  and  factor Va ). [ 1 ] [ 2 ] [ 3 ]  It is released from the  N-terminus  of prothrombin. [ 3 ]  F1+2 is a marker of  thrombin generation  and hence of  coagulation  activation. [ 4 ] [ 3 ] [ 1 ]  It is considered the best marker of  in vivo  thrombin generation. [ 1 ]


F1+2 levels can be quantified with  blood tests  and is used in the diagnosis of  hyper-  and  hypocoagulable  states and in the monitoring of  anticoagulant  therapy. [ 4 ] [ 1 ]  It was initially determined with a  radioimmunoassay , but is now measured with several  enzyme-linked immunosorbent assays . [ 1 ]


The  molecular weight  of F1+2 is around 41 to 43 kDa. [ 4 ] [ 1 ]  Its  biological half-life  is 90 minutes and it persists in blood for a few hours after formation. [ 4 ] [ 3 ] [ 1 ]  The half-life of F1+2 is relatively long, which makes it more reliable for measuring ongoing coagulation than other markers like  thrombin–antithrombin complexes  and  fibrinopeptide A . [ 1 ] [ 3 ]  Concentrations of F1+2 in healthy individuals range from 0.44 to 1.11 nM. [ 4 ]


F1+2 levels increase with  age . [ 3 ]  Levels of F1+2 have been reported to be elevated in  venous thromboembolism ,  protein C deficiency ,  protein S deficiency ,  atrial fibrillation ,  unstable angina , acute  myocardial infarction , acute  stroke ,  atherosclerosis ,  peripheral arterial disease , and in  smokers . [ 3 ] [ 1 ]  Anticoagulants have been found to reduce F1+2 levels. [ 1 ]  F1+2 levels are increased with  pregnancy [ 5 ]  and by  ethinylestradiol -containing  birth control pills . [ 6 ]  Conversely, they do not appear to be increased with  estetrol - or  estradiol-containing birth control pills . [ 6 ]  However, F1+2 levels have been reported to be increased with oral  estrogen -based  menopausal hormone therapy , whereas  transdermal  estradiol-based menpausal hormone therapy appears to result in less or no consistent increase. [ 7 ]


The  prothrombin time  ( PT ) – along with its derived measures of  prothrombin ratio  ( PR ) and  international normalized ratio  ( INR ) – is an  assay  for evaluating the  extrinsic pathway  and  common pathway  of  coagulation . This  blood test  is also called  protime INR  and  PT/INR . They are used to determine the  clotting tendency  of blood, in conditions such as the measure of  warfarin  dosage, liver damage (cirrhosis), and  vitamin K  status. PT measures the following  coagulation factors :  I (fibrinogen) ,  II (prothrombin) ,  V (proaccelerin) ,  VII (proconvertin) , and  X (Stuart–Prower factor) .


PT is often used in conjunction with the  activated partial thromboplastin time  (aPTT) which measures the  intrinsic  pathway  and common pathway of coagulation. [ citation needed ]


The reference range for prothrombin time depends on the analytical method used, but is usually around 12–13 seconds (results should always be interpreted using the reference range from the laboratory that performed the test), and the INR in absence of anticoagulation therapy is 0.8–1.2. The target range for INR in anticoagulant use (e.g.  warfarin ) is 2 to 3. In some cases, if more intense anticoagulation is thought to be required, the target range may be as high as 2.5–3.5 depending on the indication for anticoagulation. [ 1 ]


Prothrombin time is typically analyzed by a laboratory technologist on an automated instrument at 37 °C (as a nominal approximation of normal human body temperature). [ citation needed ]


The prothrombin time ratio is the ratio of a subject's measured prothrombin time (in seconds) to the normal laboratory reference PT. The PT ratio varies depending on the specific reagents used, and has been replaced by the INR. [ 3 ]  Elevated INR may be useful as a rapid and inexpensive  diagnostic  of infection in people with COVID-19. [ 4 ]


The result (in seconds) for a prothrombin time performed on a normal individual will vary according to the type of analytical system employed. This is due to the variations between different types and batches of manufacturer's tissue factor used in the reagent to perform the test. The INR was devised to standardize the results. Each manufacturer assigns an ISI value (International Sensitivity Index) for any tissue factor they manufacture. The ISI value indicates how a particular batch of tissue factor compares to an international reference tissue factor. The ISI is usually between 0.94 and 1.4 for more sensitive and 2.0–3.0 for less sensitive thromboplastins. [ 5 ] [ 6 ] [ 7 ]


The INR is the ratio of a patient's prothrombin time to a normal (control) sample, raised to the power of the ISI value for the analytical system being used.


PT normal  is established as the geometric mean of the prothrombin times (PT) of a reference sample group. [ 8 ]


The prothrombin time is the time it takes  plasma  to clot after addition of  tissue factor  (obtained from animals such as rabbits, or recombinant tissue factor, or from brains of autopsy patients). This measures the quality of the  extrinsic pathway  (as well as the  common pathway ) of  coagulation . The speed of the  extrinsic pathway  is greatly affected by levels of functional  factor VII  in the body. Factor VII has a short  half-life  and the  carboxylation  of its  glutamate  residues requires  vitamin K . The prothrombin time can be prolonged as a result of deficiencies in vitamin K,  warfarin  therapy,  malabsorption , or lack of intestinal colonization by bacteria (such as in  newborns ). In addition, poor factor VII synthesis (due to  liver disease ) or increased consumption (in  disseminated intravascular coagulation ) may prolong the PT. [ citation needed ]


The INR is typically used to monitor patients on warfarin or related oral anticoagulant therapy.  The normal range for a healthy person not using warfarin is 0.8–1.2, and for people on warfarin therapy an INR of 2.0–3.0 is usually targeted, although the target INR may be higher in particular situations, such as for those with a  mechanical heart valve . If the INR is outside the target range, a high INR indicates a higher risk of bleeding, while a low INR suggests a higher risk of developing a clot. In patients on a vitamin K antagonist such as warfarin with supratherapeutic INR but INR less than 10 and no bleeding, it is enough to lower the dose or omit a dose, monitor the INR and resume the vitamin K antagonist at an adjusted lower dose when the target INR is reached. [ 9 ]  For people who need rapid reversal of the vitamin K antagonist – such as due to serious bleeding – or who need emergency surgery, the effects of warfarin can be reversed with vitamin K,  prothrombin complex concentrate  (PCC), or  fresh frozen plasma  (FFP). [ 10 ]


Lupus anticoagulant , a circulating inhibitor predisposing for thrombosis, may skew PT results, depending on the assay used. [ 11 ]  Variations between various thromboplastin preparations have in the past led to decreased accuracy of INR readings, and a 2005 study suggested that despite international calibration efforts (by INR) there were still statistically significant differences between various kits, [ 12 ]  casting doubt on the long-term tenability of PT/INR as a measure for anticoagulant therapy. [ 13 ]  Indeed, a new prothrombin time variant, the Fiix prothrombin time, intended solely for monitoring warfarin and other vitamin K antagonists has been invented [ 14 ]  and recently become available as a manufactured test. The Fiix prothrombin time is only affected by reductions in factor II and/or factor X and this stabilizes the anticoagulant effect and appears to improve clinical outcome according to an investigator initiated randomized blinded clinical trial, The Fiix-trial. [ 15 ]  In this trial thromboembolism was reduced by 50% during long-term treatment and despite that bleeding was not increased.


An estimated 800 million PT/INR assays are performed annually worldwide. [ 13 ]


In addition to the laboratory method outlined above, near-patient testing (NPT) or home INR monitoring is becoming increasingly common in some countries. In the United Kingdom, for example, near-patient testing is used both by patients at home and by some anticoagulation clinics (often hospital-based) as a fast and convenient alternative to the lab method. After a period of doubt about the accuracy of NPT results, a new generation of machines and reagents seems to be gaining acceptance for its ability to deliver results close in accuracy to those of the lab. [ 16 ]


In a typical NPT set up, a small table-top device is used. A drop of capillary blood is obtained with an automated finger-prick, which is almost painless. This drop is placed on a disposable test strip with which the machine has been prepared. The resulting INR comes up on the display a few seconds later. A similar form of testing is used by people with  diabetes  for monitoring  blood sugar  levels, which is easily taught and routinely practiced. [ citation needed ]


Local policy determines whether the patient or a coagulation specialist (pharmacist, nurse, general practitioner or hospital doctor) interprets the result and determines the dose of medication. In Germany and Austria, patients may adjust the medication dose themselves, [ citation needed ]  while in the UK and the US this remains in the hands of a health care professional.


A significant advantage of home testing is the evidence that patient self-testing with medical support and patient self-management (where patients adjust their own anticoagulant dose) improves anticoagulant control. A meta analysis which reviewed 14 trials showed that home testing led to a reduced incidence of complications (bleeding and thrombosis) and improved the time in the therapeutic range, which is an indirect measure of anticoagulant control. [ 17 ]  In 2022, a smartphone system was introduced by researchers to perform PT/INR testing in an inexpensive and accessible manner. [ 18 ]  It uses the vibration motor and camera ubiquitous on smartphones to track micro-mechanical movements of a copper particle and compute PT/INR values.


Other advantages of the NPT approach are that it is fast and convenient, usually less painful, and offers, in home use, the ability for patients to measure their own INRs when required. Among its problems are that quite a steady hand is needed to deliver the blood to the exact spot, that some patients find the finger-pricking difficult, and that the cost of the test strips must also be taken into account. In the UK these are available on prescription so that elderly and unwaged people will not pay for them and others will pay only a standard prescription charge, which at the moment represents only about 20% of the retail price of the strips. In the US, NPT in the home is currently reimbursed by  Medicare  for patients with mechanical heart valves, while private insurers may cover for other indications. Medicare is now covering home testing for patients with chronic atrial fibrillation. Home testing requires a doctor's prescription and that the meter and supplies are obtained from a Medicare-approved Independent Diagnostic Testing Facility (IDTF). [ citation needed ]


There is some evidence to suggest that NPT may be less accurate for certain patients, for example those who have the  lupus anticoagulant . [ 19 ]


International guidelines were published in 2005 to govern home monitoring of oral anticoagulation by the International Self-Monitoring Association for Oral Anticoagulation. [ 20 ]  The international guidelines study stated, "The consensus agrees that patient self-testing and patient self-management are effective methods of monitoring oral anticoagulation therapy, providing outcomes at least as good as, and possibly better than, those achieved with an anticoagulation clinic. All patients must be appropriately selected and trained. Currently, available self-testing/self-management devices give INR results which are comparable with those obtained in laboratory testing."


Medicare coverage for home testing of INR has been expanded in order to allow more people access to home testing of INR in the US. The release on 19 March 2008 said, "[t]he Centers for Medicare & Medicaid Services (CMS) expanded Medicare coverage for home blood testing of prothrombin time (PT) International Normalized Ratio (INR) to include beneficiaries who are using the drug warfarin, an anticoagulant (blood thinner) medication, for chronic atrial fibrillation or venous thromboembolism." In addition, "those Medicare beneficiaries and their physicians managing conditions related to chronic atrial fibrillation or venous thromboembolism will benefit greatly through the use of the home test." [ 21 ]


The prothrombin time was developed by  Armand J. Quick  and colleagues in 1935, [ 22 ]  and a second method was published by  Paul Owren  [ no ] , [ 23 ]  also called the "p and p" or "prothrombin and proconvertin" method. It aided in the identification of the  anticoagulants   dicumarol  and  warfarin , [ 24 ]  and was used subsequently as a measure of activity for warfarin when used therapeutically.


The INR was invented in the early 1980s by Tom Kirkwood working at the UK National Institute for Biological Standards and Control (and subsequently at the UK National Institute for Medical Research) to provide a consistent way of expressing the prothrombin time ratio, which had previously suffered from a large degree of variation between centres using different reagents. The INR was coupled to Dr Kirkwood's simultaneous invention of the International Sensitivity Index (ISI), which provided the means to calibrate different batches of thromboplastins to an international standard. [ 25 ]  The INR became widely accepted worldwide, especially after endorsement by the World Health Organization. [ 26 ]


A  radioallergosorbent test  ( RAST ) is a blood test using  radioimmunoassay test  to detect specific  IgE  antibodies in order to determine the substances a subject is  allergic  to. This is different from a  skin allergy test , which determines allergy by the reaction of a person's skin to different substances. [ citation needed ]


The two most commonly used methods of confirming allergen sensitization are skin testing and allergy blood testing. Both methods are recommended by the NIH guidelines and have similar diagnostic value in terms of sensitivity and specificity. [ 1 ] [ 2 ]


Advantages of the allergy blood test range from: excellent reproducibility across the full measuring range of the calibration curve, it has very high specificity as it binds to allergen specific IgE, and extremely sensitive too, when compared with skin prick testing. In general, this method of blood testing (in-vitro, out of body) vs skin-prick testing (in-vivo, in body) has a major advantage: it is not always necessary to remove the patient from an antihistamine medication regimen, and if the skin conditions (such as  eczema ) are so widespread that allergy skin testing cannot be done. Allergy blood tests, such as ImmunoCAP, are performed without procedure variations, and the results are of excellent standardization. [ 3 ]


Adults and children of any age can take an allergy blood test. For babies and very young children, a single needle stick for allergy blood testing is often more gentle than several skin tests. However, skin testing techniques have improved. Most skin testing does not involve needles and typically skin testing results in minimal patient discomfort. [ citation needed ]


Drawbacks to RAST and ImmunoCAP techniques do exist. Compared to skin testing, ImmunoCAP and other RAST techniques take longer to perform and are less cost effective. [ 4 ]  Several studies have also found these tests to be less sensitive than skin testing for the detection of clinically relevant allergies. [ 5 ]   False positive results may be obtained due to  cross-reactivity  of homologous proteins or by  cross-reactive carbohydrate determinants  (CCDs). [ 6 ]


In the NIH food guidelines issued in December 2010 it was stated that  "The predictive values associated with clinical evidence of allergy for ImmunoCAP cannot be applied to other test methods." [ 7 ]  With over 4000 scientific articles using ImmunoCAP and showing its clinical value, ImmunoCAP is perceived as "Gold standard" for in vitro IgE testing [ 8 ] [ 9 ]


The RAST is a  radioimmunoassay test  to detect specific  IgE  antibodies to suspected or known  allergens  for the purpose of guiding a diagnosis about allergy. [ 10 ] [ 11 ]  IgE is the  antibody  associated with  Type I allergic response : for example, if a person exhibits a high level of IgE directed against  pollen , the test may indicate the person is allergic to pollen (or pollen-like) proteins. A person who has outgrown an allergy may still have a positive IgE years after exposure. [ citation needed ]


The suspected allergen is bound to an insoluble material and the patient's serum is added. If the serum contains antibodies to the allergen, those antibodies will bind to the allergen. Radiolabeled anti-human IgE antibody is added where it binds to those IgE antibodies already bound to the insoluble material. The unbound anti-human IgE antibodies are washed away. The amount of radioactivity is proportional to the serum IgE for the allergen. [ 12 ]


RASTs are often used to test for allergies when:


The RAST is scored on a scale from 0 to 6:


The market-leading RAST methodology was invented and marketed in 1974 by  Pharmacia Diagnostics AB , Uppsala, Sweden, and the acronym RAST is actually a brand name. In 1989, Pharmacia Diagnostics AB replaced it with a superior test named the ImmunoCAP Specific IgE blood test, which literature may also describe as: CAP RAST, CAP FEIA ( fluorenzymeimmunoassay ), and Pharmacia CAP. A review of applicable quality assessment programs shows that this new test has replaced the original RAST in approximately 80% of the world's commercial clinical laboratories, where specific IgE testing is performed. The newest version, the ImmunoCAP Specific IgE 0–100, is the only specific IgE assay to receive FDA approval to quantitatively report to its detection limit of 0.1kU/L. This clearance is based on the CLSI/NCCLS-17A Limits of Detection and Limits of Quantitation, October 2004 guideline. [ citation needed ] The guidelines for diagnosis and management of food allergy issues by the National Institute of Health state that:


In 2010 the United States  National Institute of Allergy and Infectious Diseases  recommended that the RAST measurements of specific immunoglobulin E for the diagnosis of allergy be abandoned in favor of testing with more sensitive fluorescence enzyme-labeled assays. [ 13 ]


A  random glucose test , also known as a  random blood glucose test  ( RBG test ) or a  casual blood glucose test  ( CBG test ) is a  glucose test  (test of  blood sugar level ) on the blood of a non- fasting  person. This test assumes a recent  meal  and therefore has higher  reference values  than the fasting blood glucose (FBG) test.


Most mentions of  capillary blood glucose  (CBG) tests refer to random, nonfasting instances thereof, but the real distinction in that term is capillary blood glucose versus venous blood glucose, arterial blood glucose, or interstitial fluid glucose; any fingerstick or optical transdermal glucose test, fasting or nonfasting, measures capillary blood glucose level.


The reference values for a "normal" random glucose test in an average adult are 80–140 mg / dl  (4.4–7.8  mmol /l), between 140 and 200 mg / dl  (7.8–11.1  mmol /l) is considered pre-diabetes [ citation needed ] , and ≥ 200  mg / dl  is considered diabetes according to ADA guidelines [ 1 ]  (you should visit your doctor or a clinic for additional tests however as a random glucose of > 160 mg / dl  does not necessarily mean you are diabetic). [ citation needed ]


Red blood cell distribution width  ( RDW ), as well as various types thereof ( RDW-CV  or  RCDW  and  RDW-SD ), is a measure of the range of variation of  red blood cell  (RBC) volume that is reported as part of a standard  complete blood count . [ 1 ]  Red blood cells have an  average volume  of 80–100 femtoliters, but individual cell volumes vary even in healthy blood. [ 1 ]  Certain disorders, however, cause a significantly increased variation in cell size. Higher RDW values indicate greater variation in size. Normal  reference range  of RDW-CV in human red blood cells is 11.5–15.4%. [ 2 ] [ 1 ]  If  anemia  is observed, RDW test results are often used together with  mean corpuscular volume  (MCV) results to determine the possible causes of the anemia. It is mainly used to differentiate an anemia of mixed causes from an anemia of a single cause.


Deficiencies of  Vitamin B 12  or  folate  produce a  macrocytic anemia  (large cell anemia) in which the RDW is elevated in roughly two-thirds of all cases. However, a varied size distribution of red blood cells is a hallmark of iron deficiency anemia, and as such shows an increased RDW in virtually all cases. In the case of both iron and B 12  deficiencies, there will normally be a mix of both large cells and small cells, causing the RDW to be elevated. An elevated RDW (red blood cells of unequal sizes) is known as  anisocytosis . [ 3 ]


An elevation in the RDW is not characteristic of all anemias.  Anemia of chronic disease ,  hereditary spherocytosis ,  acute blood loss ,  aplastic anemia  (anemia resulting from an inability of the bone marrow to produce red blood cells), and certain  hereditary hemoglobinopathies  (including some cases of  thalassemia minor ) may all present with a normal RDW. [ 4 ]


The "width" in RDW is sometimes thought to be "misleading", since it in fact is a measure of deviation of the  volume  of RBCs, and not directly the diameter. RDW-CV "width" refers to the width of the volume curve (distribution width), not the width of the cells.
 [ 5 ] [ 6 ]


RDW-SD is calculated as the width (in fL) of the RBC size distribution histogram at the 20% height level. This parameter is, therefore, not influenced by the average RBC size ( mean corpuscular volume , MCV). [ 7 ]


RDW-CV (expressed in %) is calculated with the following formula:


Since RDW-CV is mathematically derived from MCV, it is therefore affected by the average RBC size (MCV). [ 7 ]


Anemia in the presence of a normal RDW may suggest  thalassemia . A low  Mentzer Index , calculated from CBC data [MCV/RBC < 13], may suggest this disorder but a hemoglobin electrophoresis would be diagnostic. Anemia of chronic diseases show normal RDW. [ citation needed ]


High RDW may be a result of the presence of fragments, groups of agglutination, and/or abnormal shape of red blood cells. [ 7 ]


By severity, elevated RDW can be classified as follows:


Red blood cell indices  are  blood tests  that provide information about the  hemoglobin  content and size of  red blood cells .  Abnormal values indicate the presence of  anemia  and which type of anemia it is. [ 1 ]


Mean corpuscular volume (MCV) is the average volume of a red blood cell and is calculated by dividing the  hematocrit  (Hct) by the concentration of red blood cell count. [ citation needed ]


Mean corpuscular hemoglobin (MCH) is the average amount of  hemoglobin  (Hb) per red blood cell and is calculated by dividing the hemoglobin by the red blood cell count.  [ citation needed ]


Mean corpuscular hemoglobin concentration (MCHC) is the average concentration of hemoglobin per unit volume of red blood cells and is calculated by dividing the hemoglobin by the hematocrit.  [ citation needed ]


Red blood cell distribution width (RDW or RDW-CV or RCDW and RDW-SD) is a measure of the range of variation of red blood cell (RBC) volume, yielding clues about morphology. [ citation needed ]


The reticulocyte production index (RPI) or corrected reticulocyte count (CRC) represents the true significance of the absolute reticulocyte count to provide some reflection of erythropoietic demand and supply. The immature reticulocyte fraction (IRF) goes a step further to cast more light on the same question. [ citation needed ]


In:


Reference ranges (reference intervals) for blood tests  are sets of values used by a  health professional  to interpret a set of  medical test  results from blood samples.  Reference ranges  for  blood tests  are studied within the field of  clinical chemistry  (also known as "clinical biochemistry", "chemical pathology" or "pure blood chemistry"), the area of  pathology  that is generally concerned with analysis of  bodily fluids . [ citation needed ]


Blood test results should always be interpreted using the reference range provided by the laboratory that performed the test. [ 1 ]


A  reference range  is usually defined as the set of values 95 percent of the normal population falls within (that is, 95%  prediction interval ). [ 2 ]  It is determined by collecting data from vast numbers of laboratory tests. [ citation needed ]


In this article, all values (except the ones listed below) denote  blood plasma  concentration, which is approximately 60–100% larger than the actual blood concentration if the amount inside  red blood cells  (RBCs) is negligible. The precise factor depends on  hematocrit  as well as amount inside RBCs. Exceptions are mainly those values that denote total blood concentration, and in this article they are: [ 3 ]


A few values are for inside red blood cells only:


If not otherwise specified, a reference range for a blood test is generally the  venous  range, as the standard process of obtaining a sample is by  venipuncture . An exception is for acid–base and  blood gases , which are generally given for arterial blood. [ citation needed ]


Still, the blood values are approximately equal between the arterial and venous sides for most substances, with the exception of acid–base, blood gases and drugs (used in  therapeutic drug monitoring  (TDM) assays). [ 6 ]  Arterial levels for drugs are generally higher than venous levels because of extraction while passing through tissues. [ 6 ]


Reference ranges  are usually given as what are the usual (or  normal ) values found in the population, more specifically the  prediction interval  that 95% of the population fall into. This may also be called  standard range . In contrast,  optimal (health) range  or  therapeutic target  is a reference range or limit that is based on concentrations or levels that are associated with optimal health or minimal risk of related complications and diseases. For most substances presented, the optimal levels are the ones normally found in the population as well. More specifically, optimal levels are generally close to a  central tendency  of the values found in the population. However, usual and optimal levels may differ substantially, most notably among vitamins and blood lipids, so these tables give limits on both standard and optimal (or target) ranges. In addition, some values, including  troponin I  and  brain natriuretic peptide , are given as the estimated appropriate  cutoffs  to distinguish healthy people from people with specific conditions, which here are  myocardial infarction  and  congestive heart failure , respectively, for the aforementioned substances. [ 7 ] [ 8 ] [ 9 ]


References range may vary with age, sex, race, pregnancy, [ 10 ]  diet, use of prescribed or herbal drugs and stress. Reference ranges often depend on the analytical method used, for reasons such as  inaccuracy , lack of  standardisation , lack of  certified reference material  and differing  antibody reactivity . [ 11 ]  Also, reference ranges may be inaccurate when the reference groups used to establish the ranges are small. [ 12 ]


Smaller, narrower boxes indicate a more tight homeostatic regulation when measured as  standard "usual" reference range .


Hormones predominate at the left part of the scale, shown with a red at ng/L or pmol/L, being in very low concentration. There appears to be the greatest cluster of substances in the yellow part (μg/L or nmol/L), becoming sparser in the green part (mg/L or μmol/L). However, there is another cluster containing many metabolic substances like cholesterol and glucose at the limit with the blue part (g/L or mmol/L). [ citation needed ]


The unit conversions of substance concentrations from the molar to the mass concentration scale above are made as follows:


where distance is the direct (not logarithmic) distance in number of  decades  or "octaves" to the right the mass concentration is found. To translate from mass to molar concentration, the dividend ( molar mass  and the divisor (1000) in the  division  change places, or, alternatively,  distance to right  is changed to  distance to left . Substances with a molar mass around 1000g/mol (e.g. thyroxine) are almost vertically aligned in the mass and molar images. Adrenocorticotropic hormone, on the other hand, with a molar mass of 4540, [ 13 ]  is 0.7 decades to the right in the mass image. Substances with molar mass below 1000g/mol (e.g. electrolytes and metabolites) would have "negative" distance, that is, masses deviating to the left.
Many substances given in mass concentration are not given in molar amount because they haven't been added to the article.