docs/annotation_guidelines.md

OHCA Annotation Guidelines

Overview

This document provides comprehensive guidelines for manually annotating discharge notes to identify Out-of-Hospital Cardiac Arrest (OHCA) cases.

Definition of OHCA

Out-of-Hospital Cardiac Arrest (OHCA) is a cardiac arrest that occurs outside a healthcare facility (home, workplace, public spaces, etc.).

Annotation Labels

• 1 = OHCA: Cardiac arrest that occurred outside a healthcare facility
• 0 = Non-OHCA: Everything else

Include as OHCA (Label = 1)

• Cardiac arrest at home
• Cardiac arrest at work
• Cardiac arrest in public spaces
• Cardiac arrest witnessed by bystanders
• Cardiac arrest with CPR given outside hospital

Exclude as Non-OHCA (Label = 0)

In-Hospital Cardiac Arrests

• Cardiac arrest occurring within any healthcare facility
• Code blue called on hospital ward
• Arrest during surgery or medical procedures
• Arrest in ICU, emergency department, or any hospital unit

Transfer Cases

• All transfer cases are excluded, including:
• Patients transferred from outside hospitals for OHCA
• Patients transferred for cardiac catheterization after OHCA

Historical Cardiac Arrests

• Patients with history of cardiac arrest who did not present with current cardiac arrest

Non-Arrest Conditions

• Chest pain without cardiac arrest
• Heart attack (MI) without cardiac arrest
• Shortness of breath
• Syncope/fainting without arrest
• Any condition where cardiac arrest did not occur

Decision Tree

1. Did a cardiac arrest occur during this admission?
   └── NO → Label = 0
   └── YES → Continue to 2

2. Did the arrest happen OUTSIDE a healthcare facility?
   └── NO → Label = 0
   └── YES → Continue to 3

3. Is this a transfer case?
   └── YES → Label = 0
   └── NO → Label = 1

Confidence Scale

Rate your confidence in the annotation (1-5 scale):

• 5 = Very Confident: Clear, unambiguous case
• 4 = Confident: Strong evidence, minor uncertainty
• 3 = Moderately Confident: Some ambiguity but leaning toward decision
• 2 = Uncertain: Significant ambiguity, difficult case
• 1 = Very Uncertain: Unclear, may need expert review

Examples with Rationale

Example 1: OHCA at Home (Label = 1)

Text: "Patient found down at home by spouse, immediate CPR initiated, EMS arrived and achieved ROSC."

Rationale:

• ✅ Cardiac arrest occurred
• ✅ Outside hospital (at home)
• ✅ Not a transfer case
• Label: 1, Confidence: 5

Example 2: In-Hospital Arrest (Label = 0)

Text: "Patient admitted for pneumonia, developed cardiac arrest on day 3 of hospitalization."

Rationale:

• ✅ Cardiac arrest occurred
• ❌ Inside hospital
• Label: 0, Confidence: 5

Example 3: Transfer for OHCA (Label = 0)

Text: "Transfer from community hospital. Patient had cardiac arrest at home, CPR by family, transferred for further care."

Rationale:

• ✅ Cardiac arrest occurred outside hospital originally
• ❌ This is a transfer case
• Label: 0, Confidence: 5

Example 4: Historical Arrest (Label = 0)

Text: "Patient with history of cardiac arrest 1 year ago, now presents with chest pain."

Rationale:

• ❌ No current cardiac arrest
• ❌ Historical arrest, not current admission
• Label: 0, Confidence: 5

Example 5: Non-Arrest Condition (Label = 0)

Text: "Chief complaint: Chest pain. Patient presents with acute MI, underwent emergency PCI."

Rationale:

• ❌ No cardiac arrest occurred
• Label: 0, Confidence: 5

Example 6: Workplace Cardiac Arrest (Label = 1)

Text: "Patient collapsed at work, coworkers initiated CPR, EMS transported to hospital."

Rationale:

• ✅ Cardiac arrest occurred
• ✅ Outside hospital (at work)
• ✅ Not a transfer case
• Label: 1, Confidence: 5

Quality Control

Before Submitting

1. Double-check each decision against the criteria
2. Review cases with confidence < 3
3. Add notes for any unusual or borderline cases
4. Ensure consistency in similar cases

Notes Field

Use the notes field to document:

• Reasoning for difficult decisions
• Key phrases that influenced decision
• Uncertainties or missing information
• Questions for review

Common Mistakes to Avoid

1. Don't include in-hospital arrests
2. Don't include any transfer cases (even if transferred for OHCA)
3. Don't include historical arrests from previous admissions
4. Don't include conditions where no cardiac arrest occurred

Difficult Cases

Transfer Cases

• All transfer cases are excluded (Label = 0)
• This includes transfers specifically for OHCA management
• Focus on whether this is a transfer, not the original location of arrest

Multiple Conditions

• Focus on whether cardiac arrest actually occurred
• If no arrest mentioned, label as 0

Incomplete Information

• Base decision on available information
• Use lower confidence score
• Add notes about missing information

Support

If you encounter cases that don't fit these guidelines:

1. Make your best judgment
2. Use a lower confidence score
3. Document your reasoning in notes
4. Flag for expert review if needed

Remember: Consistency is key for model training. When in doubt, err on the side of excluding (Label = 0) and document your uncertainty.

Key Principles

1. OHCA must occur outside healthcare facilities
2. All transfer cases are excluded
3. Only current cardiac arrests, not historical ones
4. No cardiac arrest = automatic exclusion
5. When uncertain, exclude and note reasons