APC-resistance as a possible predictor of recurrent thrombosis in women with Factor V Leiden

Hypothesis/aims of study. The current analysis was undertaken to elucidate the role of Factor Va resistance to proteolytic cleavage by activated protein C in FVL(1691)GA female carriers in the development of acute and recurrent thromboses. Study design, materials and methods. A prospective clinical cohort study of 1100 women of reproductive age was conducted, with the course and outcomes of 2,707 pregnancies analyzed. Two cohorts were specified: the main group consisted of 500 patients with FV(1691)GA genotype, and the control group consisted of 600 patients with FVL(1691)GG genotype. Results. FVL(1691)GA genotype was significantly associated with the development of venous thromboembolic complications (VTEC) compared to FVL(1691)GG genotype (OR 9.3; p < 0.0001). Episodes of recurrent thrombosis during and outside of pregnancy were registered only in FVL(1691)GA patients (OR 5.7, p = 0.2). In all cases, at the time of the thrombotic event and during the period before the episode of acute or recurrent thrombosis, an APC resistance normalized ratio (NR) value was ≤ 0.49, with no episodes of VTEC registered with an APC resistance NR value ≥ 0.5. Conclusion. Venous thromboses occur under the condition of expressed APC resistance with underlying FVL(1691)GA carriage. The APC resistance index can serve as an objective biochemical marker to determine the feasibility of thromboprophylaxis within the framework of personalized medicine.