SELECTIVE SCREENING FOR THE FACTOR-V-LEIDEN MUTATION - IS IT ADVISABLE PRIOR TO THE PRESCRIPTION OF ORAL-CONTRACEPTIVES

The cumulative thrombotic risk of Factor V (FV) Leiden and oral contra ceptives (OC) recommends screening for the mutation. Assuming that a f amily history of thrombosis increases the patient's likelihood of bear ing FV Leiden, a selective rather than universal screening would be pe rformed. We studied the utility of a family history of thrombosis for screening of FV Leiden before prescription of OC and, furthermore, the utility of screening even if oral contraception is favoured. 101 pati ents who had their first and single thromboembolic event while using O C were interviewed. 609 women without any history of thromboembolism r ecruited by gynecologists completed a standard questionnaire. 101 of t hese women, age-matched and currently using OC, were selected for a ca se-control study. Regarding patients with previous thromboembolism, a family history in a first-degree relative had a positive predictive va lue (PPV) of only 14% for FV Leiden. A PPV of 12% was calculated by in vestigating the 609 thrombosis-free women. Inherited FV Leiden (odds r atio = 4.9) and acquired risk factors (odds ratio = 10.1) were both fo und to be the most prominent, but independent additional risks. Nevert heless, FV Leiden carriers, both heterozygotes and homozygotes, did no t suffer earlier from thromboembolism than patients without the mutati on. In conclusion, family history is an unreliable criterion to detect FV Leiden carriers. Screening for factor V Leiden can be worthwhile e ven if the advantages of oral contraception are higher assessed than t he thrombotic risk. Affected women knowing about their additional risk could contribute to the prevention of thrombosis in risk situations.