The following is a summary of “Subarachnoid haemorrhage in the emergency department (SHED): a prospective, observational, multicentre cohort study,” published in the September 2024 issue of Emergency Medicine by Roberts et al.

Researchers conducted a retrospective study to externally validate the international guideline of brain imaging within 6 hours of headache onset to exclude subarachnoid hemorrhage (SAH) and to evaluate the test characteristics of CT-brain beyond 6 hours.

They examined adult patients with non-traumatic acute headaches contributing to the ED in a UK National Health Service setting. Investigations, diagnoses, and management of SAH were executed according to regular practice. Participants were followed up for 28 days via medical records and direct contact as needed, with uncertain diagnoses independently adjudicated.

The results showed that between March 2020 and February 2023, 3,663 suitable patients (mean age 45.8 years [SD 16.6], 64.1% female) were enlisted in 88 EDs, from which 3,268 patients (89.2%) had CT-brain imaging, confirming 237 cases of SAH, with 6.5% of prevalence. CT conducted within 6 hours of headache onset (n=772) demonstrated a sensitivity of 97% (95% CI 92.5% to 99.2%) for SAH diagnosis and an adverse predictive value of 99.6% (95% CI 98.9% to 99.9%), with a post-test probability of 0.5% (95% CI 0.2% to 1.3%) and a negative probability ratio of 0.03 (95% CI 0.01 to 0.08). CT within 24 hours of headache onset (n=2,008) showed a sensitivity of 94.6% (95% CI 91.0% to 97.0%), with a consistently lower post-test probability for SAH of less than 1% and a 0.1% (95% CI 0.0% to 0.4%) probability for aneurysmal SAH if the CT was performed within 24 hours of headache onset.

They concluded a negative CT-brain scan performed early after headache onset indicated a low likelihood of SAH, which could guide shared decision-making regarding further investigation in ED patients with acute headaches.

Source: emj.bmj.com/content/early/2024/09/12/emermed-2024-214068