Supplementary Material for: Is Intra-Arterial Treatment for Acute Ischemic Stroke Less Effective in Women than in Men?

<i>Introduction:</i> Stroke etiology and outcome after ischemic stroke differ between men and women. We examined if sex modifies the effect of intra-arterial treatment (IAT) in a randomized clinical trial of IAT for acute ischemic stroke in the Netherlands (MR CLEAN). <i>Patients and Methods:</i> The primary outcome was the score on the modified Rankin scale at 90 days. We tested for interaction between sex and treatment and estimated the treatment effect by sex with multiple ordinal logistic regression with adjustment for prognostic factors. <i>Results:</i> All 500 patients were included in the analysis; 292 (58.4%) were men. The treatment effect (adjusted common odds ratio) was 2.39 [95% confidence interval (CI) 1.55-3.68] in men and 0.99 (95% CI 0.60-1.66) in women (pinteraction = 0.016). In women, mortality was higher in the intervention group than in the control group (24 vs. 15%, p = 0.07). Serious adverse events occurred more often in women than in men undergoing intervention. There were no differences in neuro-imaging outcomes. <i>Discussion and Conclusion:</i> Contrary to other studies, we found a significant interaction between sex and treatment effect in the MR CLEAN trial. Pooled analyses of all published thrombectomy trials did not confirm this finding. In MR CLEAN, women seem to have a slightly more unfavorable profile, causing higher mortality and more serious adverse events, but insufficient to explain the absence of an overall effect. This suggests a play of chance and makes it clear that IAT should not be withheld in women.