Summary

Factor V Leiden and factor II G20210A mutations are two frequentgenetic risk factors involved in venous thromboembolism (VTE). Thegoal of this pooled analysis of 8 case-control studies, comprising a totalof 2310 cases and 3204 controls, was to precisely estimate the risk ofVTE in patients bearing both mutations (double heterozygotes). Oddsratios for VTE were 4.9 (95% CI; 4.1-5.9) for the factor V Leiden and3.8 (3.0-4.9) for the factor II G20210A mutation. Fifty-one cases (2.2%)and none of the controls were double heterozygotes. The odds ratio forvenous thrombosis in double heterozygotes was 20.0 (11.1-36.1).Twelve percent of patients heterozygous for factor V Leiden were alsoheterozygous for factor II G20210A and conversely 23% of patientsheterozygous for factor II G20210A were also heterozygous for factorV Leiden. Furthermore, in this large population we analyzed the effectof oral contraceptive (OC) in women carrying one of these mutations.Odds ratio for VTE associated with OC was 2.29 (1.72-3.04). In factorV Leiden carriers using OC, the odds ratio for VTE was 10.25(5.69-18.45). The odds ratio of the association of factor II mutation andOC use was 7.14 (3.39-15.04). Finally, we also confirmed that thefrequency of factor V Leiden was lower in patients with pulmonaryembolism than in patients with deep vein thrombosis without PE (odds