Clinical decision rule highly sensitive in predicting subarachnoid hemorrhage

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1. The Ottawa Subarachnoid Hemorrhage Rule is highly sensitive in predicting subarachnoid hemorrhage in patients with normal neurological exams who present to the emergency department with acute nontraumatic headache peaking in one hour. 

2. Subarachnoid hemorrhage can be predicted with 100% sensitivity by including “thunderclap headache” and “limited neck flexion” to patients who are 40 years or older with neck pain or stiffness, loss of consciousness, or headache onset during exertion. 

Evidence Rating Level: 1 (Excellent)     

Study Rundown:  Subarachnoid hemorrhage (SAH) is a life-threatening emergency that can be missed in emergency department visits due to lack of consensus on characteristics that differentiate it from headaches of other etiologies. The primary objective of this study was to evaluate three previously derived clinical decision rules to identify characteristics that predicted SAH in adult patients presenting with acute, nontraumatic headaches reaching maximal intensity in one hour.  A prediction rule with 98.5% sensitivity and 27.5% specificity for SAH was identified with the following inclusion criteria: patients who were neurologically intact, age 40 years or older with neck pain or stiffness, loss of consciousness, or headache onset during exertion. The Ottawa SAH Rule was created by adding additional criteria of “thunderclap headache” and “limited neck flexion on exam” resulting in a prediction rule with 100% sensitivity and 15.3% specificity. This rule was deemed the most sensitive, reliable, and clinically acceptable potential rule for future implementation studies. The study informs clinical practice by standardizing characteristics that define patients who should be further evaluated for SAH. Increasing the sensitivity of the prediction rule may lead to increased testing and associated costs. Implementation studies are required before the rule can be routinely applied in clinical practice.

Click to read the study published today in JAMA

Relevant Reading: High-risk clinical characteristics for subarachnoid haemorrhage in patients with acute headache: prospective cohort study

In-Depth [prospective cohort study]: This study evaluated 2131adult patients presenting with acute nontraumatic headaches to 10 university-affiliated Canadian emergency departments from 2006 – 2010. ED physicians used one of three clinical decision rules that were separately derived from a previous cohort study. Using the clinical decision rule with patients who were age 40 years or older with neck pain or stiffness, loss of consciousness, or headache onset during exertion had a sensitivity of 98.5% (95% CI, 94.6%-99.6%), specificity of 27.6% (95% CI, 25.7%-29.6%), and interobserver agreement of 0.86 (95% CI, 0.70-1) in predicting SAH. The Ottawa SAH Rule was created by further including the variables “thunderclap head- ache” (defined as instantly peaking pain) and limited neck flexion on examination (defined as inability to touch chin to chest or raise the head 8 cm off the bed if supine), resulting in a sensitivity of 100% (95% CI, 97.2%-100.0%), specificity of 15.3% (95% CI, 13.8%-16.9%), and interobserver agreement of 0.60 (95% CI, 0.59- 0.61).

By Gayatri Boddupalli and Brittany Hasty

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