ottawa_sah_rule: Ottawa Subarachnoid Hemorrhage (SAH) Rule

In cliot: Clinical Indices and Outcomes Tools

Ottawa Subarachnoid Hemorrhage (SAH) Rule

Description

Calculates the Ottawa SAH Rule result for patients presenting with acute non-traumatic headache. This clinical decision rule has 100% sensitivity for subarachnoid hemorrhage, allowing clinicians to rule out SAH without further investigation (CT/LP) if all criteria are absent.

Usage

ottawa_sah_rule(age, neck_pain_stiffness, witnessed_loc, onset_exertion,
                thunderclap_headache, limited_neck_flexion)

Arguments

age	Numeric. Patient age in years. (>= 40 is a high-risk criterion).
neck_pain_stiffness	Numeric (0 or 1). Patient reports neck pain or stiffness? (1 = Yes).
witnessed_loc	Numeric (0 or 1). Was there witnessed loss of consciousness? (1 = Yes).
onset_exertion	Numeric (0 or 1). Did the headache start during exertion? (1 = Yes).
thunderclap_headache	Numeric (0 or 1). Was it a thunderclap headache (instantly peaking pain)? (1 = Yes).
limited_neck_flexion	Numeric (0 or 1). Is there limited neck flexion on physical examination? (1 = Yes).

Value

A list containing:

Result	Recommendation regarding the need for investigation (Investigate vs. Rule Out).
Criteria_Met	List of specific criteria that triggered a positive result.

References

Perry JJ, Stiell IG, Sivilotti ML, et al. Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA. 2013;310(12):1248-1255. doi:10.1001/jama.2013.278018

Examples

# Example 1: Investigate (Age >= 40)
# 45yo, No other symptoms
ottawa_sah_rule(45, 0, 0, 0, 0, 0)

# Example 2: Rule Out
# 30yo, No high risk features
ottawa_sah_rule(30, 0, 0, 0, 0, 0)

# Example 3: Investigate (Thunderclap)
# 25yo, Thunderclap headache
ottawa_sah_rule(25, 0, 0, 0, 1, 0)

cliot documentation built on Dec. 1, 2025, 1:06 a.m.