Prevalence of the G1691A mutation in the factor V gene (factor V Leiden) and the G20210A prothrombin gene mutation in the Thai population.

We investigated the prevalence of a genetic variation in the factor V gene (G1691A Leiden mutation) and the prothrombin gene (G20210A) using polymerase chain reaction techniques in samples from 500 normal Thai population and among 50 unselected Thai patients with an objectively confirmed history of deep venous thrombosis. The prevalence of factor V Leiden and the prothrombin G20210A gene mutation in a group of 500 healthy controls was 0.2% in both groups (allele frequency of 0.1%). Of the 50 adult patients studied, none was a carrier of factor V Leiden or the prothrombin G20210A gene mutation. Our findings confirm that the prevalence of factor V Leiden and prothrombin G20210A gene mutation is lower among Asians than Caucasians and that the distribution of factor V Leiden is similar to that of the prothrombin G20210A variant. The low prevalence of these two mutations can, at least in part, account for the lower frequency of deep venous thrombosis reported in the Thai population. Screening for factor V Leiden and prothrombin gene mutation is of limited benefit and may not be cost-effective in Thai patients with the first episode of deep venous thrombosis.