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.
1. Does The Patient Meet All Inclusion Criteria and No Exclusion Criteria?
Age ≥ 15
New, severe nontraumatic headache
Maximum intensity within 1 hour
New neurologic deficit
Known brain tumor
History of recurrent headaches