Methods:

The investigators formed the HERMES (Highly Effective Reperfusion evaluated in Multiple Endovascular Stroke Trials) collaboration to pool patient-level data from five trials (MR CLEAN, ESCAPE, REVASCAT, SWIFT PRIME, and EXTEND IA) conducted between December 2010, and December 2014. In these trials, patients with acute ischemic stroke caused by occlusion of the proximal anterior artery circulation were randomly assigned to receive either endovascular thrombectomy within 12 hours of symptom onset or standard care (control), with a primary outcome of reduced disability on the modified Rankin Scale (mRS) at 90 days. By direct access to the study databases, the authors extracted individual patient data that were used to assess the primary outcome of reduced disability on mRS at 90 days in the pooled population and examine heterogeneity of this treatment effect across prespecified subgroups. To account for between-trial variance, they used mixed-effects modeling with random effects for parameters of interest. The authors then used mixed-effects ordinal logistic regression models to calculate common odds ratios (cORs) for the primary outcome in the whole population (shift analysis) and in subgroups after adjustment for age, sex, baseline stroke severity (National Institutes of Health Stroke Scale score), site of occlusion (internal carotid artery vs. M1 segment of middle cerebral artery vs. M2 segment of middle cerebral artery), intravenous alteplase (yes vs. no), baseline Alberta Stroke Program Early CT score, and time from stroke onset to randomization.