New clinical decision rule could reduce misdiagnosis of deadly brain bleeding

September 25, 2013

Researchers from Ottawa, Canada have developed a simple clinical decision rule that may help emergency doctors identify which patients with headache have a dangerous subarachnoid hemorrhage or SAH (bleeding in a certain area of the brain).

The study is published in the September 25 issue of the Journal of the American Medical Association (JAMA). It is led by Dr. Jeffrey Perry, senior scientist at the Ottawa Hospital Research Institute (OHRI), emergency physician at The Ottawa Hospital (TOH) and associate professor at the University of Ottawa (uOttawa).

Subarachnoid hemorrhage affects approximately 35,000 people every year in Canada and the U.S., and approximately five per cent of these people (or 1,750) are initially misdiagnosed. Dr. Perry’s new clinical decision rule, called the Ottawa SAH Rule, has the potential to reduce the misdiagnosis rate to near zero.

“Subarachnoid hemorrhage is an extremely serious condition, resulting in death in up to half of all cases, and serious disability in many others,” said Dr. Perry. “Unfortunately it can be difficult to diagnose this condition, because the main symptom for many patients is often a simple headache.”

“Our rule can help doctors determine which headache patients should be given further tests for subarachnoid hemorrhage, and our studies show that applying this rule would reduce the rate of initial misdiagnosis to close to zero,” continued Dr. Perry. “If we can reduce misdiagnosis, we should be able to speed up treatment and save hundreds of lives every year.”

The current study involved 2,131 adult patients who visited 10 Canadian emergency departments between April 2006 to July 2010, with a headache peaking within one hour and no neurologic deficits. The researchers evaluated three clinical decision rules they had developed previously, and refined the rule to the following:

Ottawa SAH (Subarachnoid Hemorrhage) Rule

For alert patients older than 15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour.

Not for patients with new neurologic deficits, previous aneurysms, SAH, brain tumours, or history of recurrent headaches (≥ 6months).

Investigate if ≥1 high risk variables present:
1. Age ≥ 40 years
2. Neck pain or stiffness
3. Witnessed loss of consciousness
4. Onset during exertion
5. Thunderclap headache (instant peaking pain)
6. Limited neck flexion on examination

The rule was able to accurately diagnose 132 patients (6.2 per cent) with SAH, with zero missed cases. The rule was also able to modestly reduce the rate of investigation (i.e. reduce the use of CT scanning and lumbar puncture) by ruling out SAH in some headache patients.

“We recommend that emergency physicians begin using the Ottawa SAH Rule now to identify high risk patients who should be investigated for SAH, however further study is required to determine if the rule should be used to rule out SAH investigation in patients without high risk features,” said Dr. Perry.

This study was funded by the Canadian Institutes of Health Research.

Full reference: Clinical Decision Rules to Rule Out Subarachnoid Hemorrhage for Acute Headache. Perry JJ, Stiell IG, Sivilotti MLA, Bullard MJ, Hohl CM, Sutherland J, Emond M, Worster A, Lee JS, Mackey D, Pauls M, Lesiuk J, Symington C, Wells GA. JAMA, September 25, 2013.

Author affiliations include: Ottawa Hospital Research Institute, University of Ottawa, Queen’s University, University of British Columbia, Université Laval, McMaster University, University of Toronto, University of Alberta, University of Manitoba.

About the Ottawa Hospital Research Institute
The Ottawa Hospital Research Institute (OHRI) is the research arm of The Ottawa Hospital and is an affiliated institute of the University of Ottawa, closely associated with the university’s Faculties of Medicine and Health Sciences. OHRI includes more than 1,700 scientists, clinical investigators, graduate students, postdoctoral fellows and staff conducting research to improve the understanding, prevention, diagnosis and treatment of human disease.

Media contact
Jennifer Ganton
Director, Communications and Public Relations, Ottawa Hospital Research Institute
Directrice, Communications et relations publiques, Institut de recherche de l'Hôpital d'Ottawa
613-798-5555 x 73325
613-614-5253 (cell)