Is Multidetector CT Sufficient for ED Diagnosis of Subarachnoid Hemorrhage?
Newer multidetector helical CT is not sensitive enough to be used as the sole diagnostic test.
The standard emergency department work-up for subarachnoid hemorrhage (SAH) includes noncontrast head computed tomography (CT) followed by lumbar puncture (LP), if CT is negative. LP is thought to be required after a negative CT result because the reported sensitivity of CT for detecting SAH (90% to 95%) is insufficient for CT to serve as a stand-alone diagnostic modality. Recent reports that newer-generation multidetector helical CT scanners are 98% to 100% sensitive for detecting SAH have prompted some clinicians to advocate for use of these newer CT scanners alone to rule out SAH in ED patients.
Researchers retrospectively assessed the sensitivity of multidetector CT (4-slice, 4-detector) in a review of all patients who had an ED diagnosis of SAH at one academic medical center during a 3-year period. Among the 149 patients, SAH was diagnosed by a positive multidetector CT result alone in 139 patients (sensitivity, 93%) and by a positive LP result after a normal CT result in 10 patients (7%). In the subgroup of 117 patients with a diagnosis of aneurysm or arteriovenous malformation, SAH was diagnosed by a positive CT result alone in 110 (sensitivity, 94%). In the subgroup of 67 patients who had a diagnosis of aneurysm or arteriovenous malformation and who presented with headache and normal mental status, the sensitivity of CT alone was 91%.
Comment: This study shows that CT with newer-generation scanners is inadequate as a stand-alone diagnostic tool to rule out SAH in ED patients. The current practice of performing LP in patients with normal CT scans whose differential diagnosis includes SAH should not change.
— Richard D. Zane, MD, FAAEM
Published in Journal Watch Emergency Medicine June 27, 2008
Citation(s): Byyny RL et al. Sensitivity of noncontrast cranial computed tomography for the emergency department diagnosis of subarachnoid hemorrhage. Ann Emerg Med 2008 Jun; 51:697.