HEALTH ECONOMIC EVALUATION OF THROMBOPROPHYLACTIC TREATMENT WITH RIVAROXABAN OR DABIGATRAN COMPARED WITH ENOXAPARIN IN PATIENTS UNDERGOING ELECTIVE HIP- OR KNEE REPLACEMENT SURGERY

Purpose: For years subcutaneous LMWHs like enoxaparin have been the primary choice for thrombosis prevention after major orthopaedic surgery. Recently, two new oral anticoagulants, rivaroxaban and dabigatran, have been suggested as possible alternative prophylactic treatments in Norway. However, the cost-effectiveness of the two drugs remains unknown. The aim of this study was to assess the cost-effectiveness of dabigatran and rivaroxaban compared with enoxaparin for the prevention of thromboembolism after total hip replacement (THR) and total knee replacement (TKR) surgery.

Method: In order to assess the cost-effectiveness of alternative thrombo-prophylactic interventions, a decision model was developed. The model combined two modules; a decision tree for the short-term prophylaxis (90-day post-surgery time horizon) and a Markov model for the long-term complications (lifetime analysis). Efficacy estimates were based on meta-analyses of published RCTs identified by a systematic literature search. The quality of the documentation was evaluated using GRADE. Quality-of-life data were extracted from published literature. Health state costs were taken from various local data sources.  We performed probabilistic sensitivity analyses, designed as a Monte Carlo simulation with 10,000 iterations, to get an impression of the uncertainty surrounding our analyses.  

Result: In THR patients, the comparison of dabigatran with enoxaparin resulted in negative net health benefit (NHB) assuming a willingness to pay per QALY gained of USD80,000; hence it cannot be considered a cost-effective strategy relative to enoxaparin. Rivaroxaban compared with enoxaparin resulted in a cost-effectiveness of USD7,500 per QALY, which can be considered a cost-effective strategy. In TKR patients, both rivaroxaban and dabigatran were less costly but resulted in slightly fewer QALYs compared with enoxaparin (negative NHB); therefore they cannot be considered cost-effective strategies after TKR. According to the probabilistic sensitivity analyses, there are uncertainties associated with the results. Assuming a willingness to pay of USD80,000, rivaroxaban following THR had a probability of 38% and enoxaparin following TKR had a probability of 34% of being cost-effective. The analysis of expected value of perfect information on parameters (EVPIP) indicated that more research on efficacy and safety data would have the greatest impact on reducing decision uncertainty.

Conclusion: There is a great uncertainty regarding which strategy is the most cost-effective. However, rivaroxaban and enoxaparin had a slightly higher probability of being cost-effective alternatives following total hip or knee replacement, respectively.