The Cost-Effectiveness of Extended-Duration Antithrombotic Prophylaxis After Total Hip Arthroplasty
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BACKGROUND: Although the risk of thromboembolism after total hip arthroplasty continues beyond hospital discharge, the cost-effectiveness of extending prophylaxis beyond hospitalization is unclear. We compared the cost-effectiveness of an extended duration of antithrombotic prophylaxis following total hip arthroplasty, with use of low-molecular-weight heparin or warfarin administered for twenty-eight days beyond hospital discharge, in terms of incremental cost per quality-adjusted life year gained. METHODS: The economic analysis was structured around a decision tree characterizing the consequences of extended prophylaxis choices following total hip arthroplasty. The health benefits of extended antithrombotic prophylaxis, measured as the reduction in symptomatic venous thromboembolic events and deaths for each treatment alternative, were determined through a systematic review of the literature. Gains in quality-adjusted life years were based on the distribution of life years remaining for all patients undergoing total hip arthroplasty in Canada in 2003, weighted by utilities derived from the literature. The cost analysis, in 2006 Canadian dollars, took a direct payer perspective with a ninety-day time horizon. RESULTS: There was a net gain in quality-adjusted life years in both cohorts that received extended prophylaxis relative to the cohort that received no extended prophylaxis (7.5 quality-adjusted life years per 1000 patients treated with low-molecular-weight heparin and 5.5 quality-adjusted life years per 1000 patients treated with warfarin), although these gains were not significant. The net treatment costs per 1000 patients treated were $799,104 with low-molecular-weight heparin and $72,236 with warfarin. In comparison with the cohort that received no extended prophylaxis, the cost-effectiveness of low-molecular-weight heparin was $106,454 per quality-adjusted life year gained and the cost-effectiveness of warfarin was $13,115 per quality-adjusted life year gained. CONCLUSIONS: There is insufficient economic evidence to support extended thromboprophylaxis with low-molecular-weight heparin following total hip arthroplasty. Although the cost-effectiveness of warfarin was potentially quite favorable, this finding was based on limited clinical evidence. Further research is required to clarify the benefits of extended prophylaxis, particularly with warfarin. LEVEL OF EVIDENCE: Economic and decision analysis, Level I. See Instructions to Authors for a complete description of levels of evidence.
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