NEW YORK (Reuters Health) - Subarachnoid hemorrhage (SAH) can be easily overlooked in ED diagnosis, Canadian researchers report in the April issue of Stroke.

Among reasons, they say, are that the condition is not common and symptoms may initially range from being as simple as a headache to being clearly indicative of neurological problems.

"Our study found a lower misdiagnosis rate than in previous studies, which is good news," investigator Dr. Michael J. Schull told Reuters Health. "However, missing 5% of patients is still too many given the gravity of this condition."

To investigate circumstances associated with missed diagnosis, Dr. Schull and Marian J. Vermeulen of the University of Toronto studied data on all 1507 SAH patients admitted to Ontario hospitals over a 3-year period.

SAH was defined as missed if the patient had had an ED visit related to SAH in the 14 days before hospital admission, but during which the diagnosis was not made.

In all, 150 patients (10%) had made such an ED visit. Of these, 81 patients (5.4%) had a missed diagnosis.

Patients who were considered to be of low acuity had a significantly increased risk of misdiagnosis (odds ratio, 2.65). In addition, SAHs were more than twice as likely to be missed in patients at non-teaching hospitals as those at teaching sites. However, the volume of SAH cases and the availability of CT had no influence on this risk.

The researchers conclude that other factors "such as physician training and experience, availability of consultants and other resources" will have to be evaluated to help develop methods of improving SAH detection rates.