Should female relatives of factor V Leiden carriers be screened prior to oral contraceptive use? A cost-effectiveness analysis.

Venous thromboembolism (VTE) is three-fold higher among FV Leiden (FVL) carriers receiving oral contraceptives (OCPs) than in the general population. FVL screening, however, is not routinely performed before prescribing OCP, and the cost-effectiveness of this strategy is unknown. A decision tree model was constructed to evaluate FVL screening and prophylactic anticoagulation (AC) strategies in female relatives of FVL carriers. In the model, AC was low molecular weight heparin, given warfarin embryopathy risks. VTE morbidity, mortality, and other clinical parameters were obtained from published studies. Drug costs were based on average wholesale price, and counseling included VTE risk with OCP use and FVL status. Outcomes included medical costs, effectiveness measured as quality-adjusted-life-years (QALY), and the incremental cost-effectiveness ratio (ICER) over 30 years, with cost and effectiveness discounted at 3%/year. FVL screening and counselling without prophylactic AC cost less and was more effective than no screening in this population, but was less effective than screening, counselling, and prophylaxis during high-risk periods, which gained 0.083 QALY, for an ICER of $147/QALY gained. Screening with counselling and long-term AC cost $3,536 with minimal QALY gain and an ICER >$600,000/QALY. Screening, OCP counseling, and prophylactic AC during high-risk periods was favoured and cost <$20,000/QALY, unless: (a) high-risk prophylaxis cost >$4,231 (base $932), (b) long-term prophylaxis cost <$1199 (base $6,546), or (c) VTE relative risk reduction with prophylaxis was <21% (base 90%). In conclusion, screening, counselling and prophylactic AC during high-risk periods in female relatives of FVL carriers is an economically favourable strategy.