Factor-V HR2 haplotype and thromboembolic disease

OBJECTIVES: The objective of this study is to evaluate the prevalence of HR2 polymorphism among patients with pulmonary embolism (PE) and healthy subjects. BACKGROUND: Polymorphism in the factor V gene named HR2 has been described as a possible risk factor for venous thromboembolism (VTE) development. Contradictive results on this association have been reported. METHODS: Eighty-five patients admitted for PE and 72 healthy subjects were included in the study. Thrombophilia screening using genetic tests for factor V Leiden (G1691A/Leiden and HR2 haplotype) and other genetic mutations were investigated. RESULTS: Of 85 patients with PE, 20 (23.53%) carried the HR2 haplotype. Further, a majority of the patients with HR2 haplotype had recurrent venous thrombosis or PE (15 out of 20 patients). The HR2 haplotype was detected in 6 (8.3%) out of 72 healthy subjects. Patients had significantly higher HR2 haplotype frequency than healthy controls (P = 0.001). HR2 carriers had a three-fold increase in risk of developing PE (OR = 3.38, 95% CI = 1.27-8.96, P = 0.011). After adjustment for other tested defects for thrombophilia, HR2 haplotype was associated with increased risk of thromboembolic events (OR = 3.05, 95% CI = 1.11-8.35, P = 0.03). However, after adjustment for sex and age, HR2 polymorphism was no longer associated with the risk of thromboembolic event (OR = 1.22, 95% CI = 0.34-4.38, P = 0.76). CONCLUSIONS: Our study does not support the notion that factor V HR2 haplotype might be a risk factor for thrombosis despite its high prevalence among patients with PE.