Cost-effectiveness of enoxaparin versus warfarin prophylaxis against deep-vein thrombosis after total hip replacement

Objective: To compare the efficacy and cost-effectiveness of enoxaparin, a low-molecular-weight heparin derivative, with that of low-dose warfarin in the prevention of deep-vein thrombosis (DVT) after total hip replacement. Data sources: English-language articles on enoxaparin and warfarin prophylaxis in patients undergoing total hip replacement published from January 1982 to December 1992. Study selection: Four trials of enoxapalin (involving 567 patients) and six trials of warfarin (involving 630) met the following criteria: randomized controlled trial, prophylaxis started no later than 24 hours after surgery and continued for at least 7 days, warfarin dose monitored and adjusted appropliately, enoxaparin dosage 30 mg twice daily, and DVT confirmed by bilateral venography. Data extraction: Rates of DVT, cost of prophylaxis, diagnosis and treatment per patient, rate of pulmonary embolism (PE), number of deaths and incremental cost-effectiveness (cost per life-year gained). Data synthesis: The pooled rate of DVT was 13.6% with enoxaparin (95% confidence interval [CI] 10.9% to 16.3%) and 20.6% with warfarin (95% CI 17.4% to 23.8%). At a cost of 19.55 per day for enoxapalin the total cost per patient, including prophylaxis and management of DVT, exceeded that per patient receiving warfarin by about $121. For every 10000 patients treated the use of enoxaparin will prevent 47 cases of DVT, 3 cases of PE and 4 deaths. Thus, the estimated incremental cost-effectiveness of enoxaparin is $29120 per life-year gained. Conclusion: On the basis of current Canadian cost-effectiveness guidelines the results of this study would be considered moderate to strong evidence to adopt enoxaparin prophylaxis against DVT after total hip replacement. However, because of the limited data the estimates are uncertain. Future trials should compare enoxaparin and warfarin and incorporate a prospective economic appraisal.