Low-molecular-weight heparin versus warfarin for secondary prophylaxis of venous thromboembolism: A cost-effectiveness analysis

PURPOSE: To compare the cost effectiveness of low-molecular-weight heparin with that of oral anticoagulants in preventing recurrences after an episode of venous thromboembolism. METHODS: A decision tree was used to assess the cost and the expected quali ty-adjusted years of life (QALY) after treatment with either low-molecular- weight heparin or warfarin, based on pooled data from six published trials. Preferences were elicited with a modified time trade-off method in a sampl e of patients attending an anticoagulation clinic. RESULTS: Compared with warfarin, low-molecular-weight heparin significantly decreased the rate of minor bleeding (odds ratio [OR] = 0.24; 95% confiden ce interval [CI]: 0.14 to 0.43) but not recurrent deep vein thromboses (OR = 0.77; 95% CI: 0.43 to 1.35). Patients' preference for warfarin (0.988, on a 0 to I scale) was lower than that for low-molecular-weight heparin (0.99 2), but the difference was not statistically significant. A Monte Carlo ana lysis estimated that low-molecular-weight heparin saved an average of 13 qu ality-adjusted days compared with warfarin, at a cost of $6,583 per QALY (9 5% CI: $5,525 to $7,625) based on costs in Italy and $28,231 per QALY (93% CI: $20,872 to $36,773) based on costs in the United States. When we includ ed rebound recurrences after interruption of therapy, which were more commo n with low-molecular-weight heparin, treatment with low-molecular-weight he parin cost $53,166 per QALY in Italy and $177,166 per QALY in the United St ates. CONCLUSIONS: Low-molecular-weight heparin might be a cost-effective drug fo r secondary prophylaxis of venous thromboembolism, especially in patients a t high risk of recurrence and where the drug's cost is lower. The apparent increase in recurrence after interruption of therapy needs to be investigat ed more thoroughly before low-molecular-weight heparin can be recommended r outinely. (C) 2001 by Excerpta Medica, Inc.