F2 and Stroke: A multivariate logistic regression analysis demonstrated that two variables were significantly relating to the onset of SAH: having previous stroke [p = 0.006; odds ratio (OR), 3.85; 95% CI, 1.73–5.06] and prothrombin time [p = 0.028; odds ratio (OR), 1.14; 95% CI, 1.02–1.29] (Supplementary Appendix Table 7).