A New Clinical Decision Rule for Subarachnoid Hemorrhage

October 2, 2013

A New Clinical Decision Rule for Subarachnoid Hemorrhage

  1. Daniel J. Pallin, MD, MPH

Pending validation in other samples, the new Ottawa SAH rule could be 100% sensitive, but would it outperform clinical judgment?

  1. Daniel J. Pallin, MD, MPH

In patients with acute headache, detection of subarachnoid hemorrhage (SAH) is important because ruptured aneurysm is the most common cause and is amenable to surgical repair. Investigators prospectively assessed the accuracy of several decision rules for SAH in a cohort of 2131 patients who had nontraumatic headache that peaked within 1 hour and normal neurologic examination findings at 10 academic urban Canadian emergency departments.

SAH was diagnosed in 132 patients (6.2%), although 35 patients (0.02%) were lost to follow-up. The final decision rule called for specific investigation of patients with any of the following characteristics: age ≥40, neck pain or stiffness, limited neck flexion, witnessed loss of consciousness, onset during exertion, or thunderclap headache (instantly peaking pain). The rule had sensitivity of 100% and specificity of 15% for identifying SAH. During actual care, 84% of the patients studied underwent computed tomography, lumbar puncture, or both, versus 86% with the rule.


This study had incredibly specific entry criteria, causing it to include a very small fraction of the headaches we see. So, practicing clinicians would be hard-pressed to find the right patients for this “rule” (if they could even remember those entry criteria). Worse yet, with a specificity of only 15% and a sensitivity no better than routine care, use of the rule is unlikely to improve outcomes or lower costs. A subarachnoid hemorrhage decision rule that outperformed clinical judgment would be great; unfortunately, this is not it.

Editor Disclosures at Time of Publication

  • Disclosures for Daniel J. Pallin, MD, MPH at time of publication Grant / research support Agency for Healthcare Research and Quality; Department of Defense; Massachusetts Coalition for the Prevention of Medical Errors; NIH


Reader Comments (3)

MD,DNB Physician, Neurology, Kalinga hospital,Bhubaneswar,India

Age 40 is too tight a criteria,there is nothing new in this article.

JONATHAN ADLER Physician, Emergency Medicine, MGH; NEJM Group
Competing Interests: Employed by NEJM Group.

Danny, nice summary of a very important article. Your comments states the rule's "...sensitivity is no better than routine care..." Sensitivity was 100%, which I think would be better than we all do now. Interesting, and disappointing, that the combined testing rate was no different - as you state.


I would disagree that SAH "is the most common cause" of an acute headache but is probably the most important common clinical cause of an acute severe headache.

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