Diagnostic Accuracy and Application of Subarachnoid Hemorrhage Decision Rules Among Patients With Non-Traumatic Acute...

The Ottawa and Emerald rules were developed to aid in the diagnosis of subarachnoid hemorrhage (SAH) and to determine whether a CT scan is necessary for patients presenting with non-traumatic acute headaches in the emergency department. Numerous studies have been conducted to validate these clinical decision rules. In this study, we aimed to investigate the pooled diagnostic accuracy of these rules and their impact on imaging utilization.

In this PRISMA-DTA-compliant systematic review, a comprehensive search was done in databases including PubMed, Scopus, Embase, and Web of Science. Then, screening, selection of studies, and data extraction were performed and the QUADAS-2 tool was used for critical appraisal. The true positives (TP), false negatives (FN), false positives (FP), and true negatives (TN) were extracted to calculate pooled sensitivity, specificity, positive likelihood ratio (LR), negative LR, and Diagnostic Odds Ratio (DOR) with 95% CIs. The effect of Ottawa rule on CT scan utilization was assessed by calculating pooled odds ratios for the number of CT scans in SAH and non-SAH groups before and after applying the rule.

The pooled sensitivity, specificity, negative LR, and positive LR for the Ottawa SAH rule were 99% (95% CI: 92%-100%), 23% (95% CI: 16%-32%), 0.025 (95% CI: 0.003%-0.193%), and 1.29 (95% CI: 1.16%-1.42%) respectively. Similarly, these measures for the Emerald SAH rule were 99% (95% CI: 71%-100%), 27% (95% CI: 15%-43%), 0.065 (95% CI: 0.004%-1.072%), and 1.34 (95% CI: 1.1%-1.62%), respectively. The pooled odds ratio for CT scan utilization for the Ottawa rule was 1.15 (95% CI: 0.62%-2.13%).

Both rules are highly sensitive for excluding SAH in patients with non-traumatic acute headaches presenting to the emergency department but have low specificity and do not significantly reduce CT scan utilization.

PROSPERO registration number: CRD42023476444.