Enter Your Email Address to Receive a
Copy of MedicExhange Member Demograhpics

Negative results on both computed tomography and lumbar puncture are sufficient to rule out subarachnoid hemorrhage.

according to what authors say is the largest study to evaluate this current clinical practice in alert emergency department patients with acute headache.

The multicenter prospective cohort study, by Canadian researchers, was published in the June issue of Annals of Emergency Medicine.

The current standard of care to rule out subarachnoid hemorrhage is head CT without contrast. If this is negative, lumbar puncture is typically performed.

The researchers enrolled 592 consecutive alert patients at least 15 years of age who presented to the emergency departments at two tertiary-care centers with a chief complaint of nontraumatic acute headache or syncope associated with a headache. Enrollment took place from November 2000 to November 2003.

Follow-up assessments were conducted at least six months following the ED visit and included a telephone call, questionnaire and an electronic search of records at the study hospital to determine if a patient had a subsequent admission or surgery for subarachnoid hemorrhage.

The mean age of patients was 43.6 years, and most (59.1 per cent) were women. The most common diagnosis (46.5 per cent) was benign headache, including tension headache, cluster migraine and nonspecific headache; migraine was also common (26.4 per cent).

Sixty-one patients had subarachnoid hemorrhage during the study period. All of the cases were identified on CT or lumbar puncture.

The diagnostic strategy had a sensitivity of 100 per cent and a specificity of 67 per cent. Although there were many false positives based on lumbar puncture results, there were no false-positive CT scans.

The researchers concluded that "in an ED headache patient at risk of subarachnoid hemorrhage, similar to those in our study with a ten per cent subarachnoid hemorrhage prevalence, a patient with a normal CT result and a normal lumbar puncture result has a posttest probability of subarachnoid hemorrhage of less than 0.0001 per cent."

Lead investigator Dr. Jeffrey Perry of the University of Ottawa told Reuters Health that he considers this study to be definitive: "It indicates with the maximal level of certainty possible in health care...that using a CT scan and a lumbar puncture is adequate to rule out a subarachnoid hemorrhage in patients similar to those enrolled in our study."

Ann Emerg Med 2008;51:707-713