Effect of the MTHFRC677T variant on risk of venous thromboembolism: interaction with factor V Leiden and prothrombin (F2G20210A) mutations.

Odds ratios for the MTHFRC677T variant were determined in a large case-control study of 558 unselected patients with venous thromboembolism and 500 control subjects. The odds ratios for MTHFRC677T heterozygosity and homozygosity were 1.07 (95%CI 0.84-1.36) and 0.71 (95%CI 0.48-1.03). In patients with the factor V Leiden or the F2G20210A mutations there was no apparent increase in risk of venous thromboembolism due to the MTHFRC677T polymorphism. Thrombophilia testing should not include genotyping for the MTHFRC677T polymorphism.