Ottawa SAH Rule

Use the Ottawa SAH Rule to rule out subarachnoid hemorrhage


Among patients presenting to the emergency department with acute nontraumatic headache that reached maximal intensity within 1 hour and who had normal neurologic examination findings, the Ottawa SAH Rule was highly sensitive for identifying subarachnoid hemorrhage.

In patients meeting the inclusion criteria, SAH was ruled out in the absence of:

  • 1. age ≥40 years
  • 2. neck pain or stiffness
  • 3. witnessed loss of consciousness
  • 4. onset during exertion
  • 5. “thunderclap headache” (ie. instantly peaking pain)
  • 6. limited neck flexion on examination

In the population studied the Ottawa SAH rule had 100% (95% CI, 97.2%-100.0%) sensitivity and 15.3% (95% CI, 13.8%-16.9%) specificity.

The authors note that the study results apply only to patients with the specific inclusion/exclusion criteria described and require additional evaluation in implementation studies before the rule is applied in routine clinical care.


Perry JJ et al.

JAMA: the Journal of the American Medical Association 2013 September 25, 310 (12): 1248-55

The Ottawa SAH Rule calculator is created by QxMD.

By using this site you acknowledge that you have read, understand, and agree to be bound by our terms of use and privacy policy. All content and tools are for educational use only, are not meant to be a substitute for professional advice and should not be used for medical diagnosis and/or medical treatment.

1. Does The Patient Meet All Inclusion Criteria and No Exclusion Criteria?

More Information

Inclusion criteria:
Age ≥ 15
New, severe nontraumatic headache
Maximum intensity within 1 hour

Exclusion criteria
New neurologic deficit
Previous aneurysm
Known brain tumor
History of recurrent headaches

0/7 completed