Background: Factor V Leiden (FVL) carriers on oral contraceptive pills (OCP) have venous thromboembolism (VTE) risks >30 times that of general population. FVL screening is not regularly performed prior to prescribing OCP. The cost-effectiveness of screening asymptomatic female relatives of FVL carriers prior to OCP use is unknown.

Methods: We constructed a decision tree model to evaluate FVL screening and prophylactic anticoagulation (AC) strategies in first degree female relatives of FVL carriers. In the model, AC was low molecular weight heparin, given warfarin embryopathy risks in pregnancy. VTE morbidity, mortality, and other clinical parameters were obtained from published studies. Drug costs were based on average wholesale price. OCP counseling covered VTE risk associated with OCP and FVL status. Outcomes included medical costs, effectiveness measured as quality-adjusted-life-years (QALY), and the incremental cost-effectiveness ratio (ICER) over a 30 year time horizon, with costs and effectiveness discounted at 3%/yr.

Results: Base case results are shown below. FVL screening and counseling without prophylactic AC (Strategy 2) gained 0.0078 QALY, for an ICER of $319/QALY gained. Screening and counseling with AC (Strategy 4) cost $3,350 with minimal QALY gain, with an ICER >$4M/QALY. Strategy 2 cost <$20K/QALY, unless: (a) screening and counseling costs were >$202 (base $50), (b) counseling reduced OCP use <23% (base 100%), or (c) VTE relative risk with FVL/OCP was <10 (base 36). Strategy 4 cost >$100K/QALY unless AC costs <$173 (base $6546 [15 yrs, discounted]).

Conclusion: Screening and counseling female relatives of FVL carriers prior to prescribing OCP is very favorable economically. Adding AC is extremely expensive, due to small effectiveness gains and high AC cost.