They reported that an increase in von Willebrand factor levels and low ADAMTS13 levels were associated with increased odds of IS and MI in young women in the RATIO cohort, with a further Table 8. Odds of Ischemic Stroke With the Presence of Genetic or Acquired Prothrombotic Factors With and Without OC Use in the RATIO Cohort Adjusted OR (95% CI) Study Case/Control, n Biomarker (Genetic or Acquired) Non-OC Users OC Users Slooter et al225 Pruissen et al226 Urbanus et al227 175/628 Lupus anticoagulant (Ratios/c Andersson et al228 ADAMTS13 indicates a disintegrin and metalloproteinase with the thrombospondin type I repeat 13; CI, confidence interval; FVL, factor V Leiden mutation; FXIII, factor XIII; MTHFR, methylenetetrahydrofolate reductase; OC, oral contraceptive; OR, odds ratio; RATIO, Risk of Arterial Thrombosis in Relation to Oral Contraceptives; Ratios/c , normalized ratios for lupus anticoagulant screen and lupus anticoagulant confirm coagulation times; and vWF, von Willebrand factor. *Adjusted for age, residence area, and index year. Adjusted for age at index date, index year, area of residence, hypercholesterolemia, hypertension, diabetes mellitus, and smoking. Adjusted for age, year of event/index year, area of residence, hypercholesterolemia, hypertension, diabetes mellitus, and smoking. increase in the OR with OC use.228 The largest effect of OC use was in women with von Willebrand factor levels >90th percentile, for whom the OR for stroke was 1.6 (95% CI, 0.8 3.5) in nonusers and increased to 11.4 (95% CI, 5.2 25.3) in OC users. The results of this study demonstrate that OC use appears to further increase the risk of stroke in the set- ting of endothelial dysfunction. 