The impact of heterozygosity for the factor V Leiden and factor II G20210A mutations on the risk of thrombosis in Greek patients

Aim. There is growing evidence that a number of genetic risk factors predispose independently to venous thrombosis and the coexistence of defective genes is involved in the manifestation and recurrence of thrombotic events. The goal of this study was to examine the efficiency of the selection criteria for performing a genetic test for the factor V G1691A (Leiden) and factor II G20210A mutations. Methods. Blood samples were drawn from 119 patients referred to us by their physicians. FV and prothrombin (FII) mutations were detected by polymerase chain reaction (PCR) followed by digestion with restriction endonucleases MnII (FV), HindIII and MspI (FII). Results. Patient carrier frequencies were 16.8% and 10.08% for FV Leiden and FII G20210A, respectively. Heterozygosity for FII G20210A was observed in 10.0% of FV Leiden carriers whereas FV Leiden homozygosity was noted in 1.68% of the patients. Genotype frequencies were in conformity with Hardy-Weinberg equilibrium by the X 2 goodness of fit test. Conclusion. The obtained data provided a substantial genetic explanation of the thrombotic phenotype in approximately 25% of the patients and thus the physicians selection criteria were sufficient for genetic testing. Furthermore, coinheritance of both genetic defects were significantly associated with increased thrombosis risk and that of recurrent thrombosis.