Evaluation of recurrent venous thromboembolism in patients with Factor V Leiden mutation in heterozygous form.

INTRODUCTION: To evaluate the risk for recurrence after first venous thromboembolism (VTE) among patients with or without Factor V Leiden (FVL) mutation.

MATERIALS AND METHODS: A prospective population based study of 1465 consecutive unselected VTE patients was performed at Skåne University Hospital 1998-2008. The VTE was objectively verified and the patients answered questionnaire and left blood samples for evaluation.

RESULTS: Out of 1465 patients (721[49%] men and 744[51%] women) thrombophilia data were available for 1267, and FVL mutation was found in heterozygous form in 339 (27). The homozygous form and prothrombin mutation (PTM) were much less common. Patients were followed during 4.8±2.3years (total 6133 patient years) and recurrence after first VTE (evaluated in 1108 patients) occurred in 131 (12%, 95%CI 10-14%), where of 49(37%) had heterozygous FVL mutation and 57(44%) were without thrombophilia. The remaining 25(19%) patients had either PTM, FVL in homozygous form, compound PTM/FVL or unknown thrombophilia status. Having FVL mutation in heterozygous form significantly increased the risk for VTE recurrence (odds ratio 2.4 (95 %CI 1.6-3.6; p<0.01). In a Kaplan-Meier analysis the FVL group also differed significantly (p<0.01) from the other patients concerning time to recurrence (almost 25% vs. 10% after 8years).

CONCLUSIONS: FVL mutation in heterozygous form is common among VTE patients and significantly increases the risk for VTE recurrence.