Factor V Leiden prevalence in venous thromboembolism patients

Recent findings have demonstrated a high frequency of activated protein C resistance in patients suffering from deep venous thrombosis (DVT). This abnormality has been related to a mutation in the factor V gene (at nucleotide position 1,691, guanine to adenine [G-->A] substitution).

To assess the frequency of the mutation in unselected inpatients with a proved DVT. To study the clinical characteristics of such patients.

All consecutive patients admitted to the hospital because of a clinical suspicion of DVT were eligible. Diagnosis of DVT with the help of venous ultrasound imaging or venography. Ventilation and perfusion lung scan was performed in all patients, and interpreted according to the Prospective Investigation of Pulmonary Embolism Diagnosis criteria; in patients with a low- or intermediate-probability lung scan, pulmonary angiography was requested. Polymerase chain reaction amplification was performed in patients with a proved DVT. A control group consisted of bone marrow volunteer donors.

From July 1994 to November 1995, 165 patients were included. Thrombosis was considered as distal in 77 and proximal in 88; an associated pulmonary embolism (PE) was found in 75 patients. Of 165 patients, 24 (14.5%) showed the factor V gene mutation (95% confidence interval, 9.4 to 19.8); the mutation was present in 3.5% of 200 bone marrow volunteer donors; odds ratio for having DVT in the presence of the mutation was 4.1. No difference in the level of DVT, or the presence of an associated PE was observed according to the presence of the mutation. Patients with the mutation have a significantly more frequent history of DVT (p=0.04) and more previous reported episodes (1.1 vs 0.6; p=0.04).

The factor V mutation is frequent in unselected DVT patients. No difference in the severity of the thrombosis episode was observed in these patients.