Evaluating the claim of enhanced persistence: the case of osteoporosis and implications for payers

Cost-effectiveness analysis (CEA) has been widely used in evaluating treatments for osteoporosis. To study the claim of enhanced persistence, this research determined the effects of persistence (the proportion of individuals who remain on treatment) and efficacy on incremental cost-effectiveness ratios (ICERs) for bisphosphonate treatment relative to no bisphosphonate treatment in the United States. For 2 age groups, 55 to 59 and 75 to 79, the authors relied on published fracture rates and applied them to 1000 postmenopausal osteoporotic patients with bone mineral density (BMD) T score < or = -2.5 during 3 years of treatment. After developing an algebraic ICER, with effectiveness measured by either quality-adjusted life years (QALYs) gained or number of fractures averted, they determined the effects of persistence and efficacy and then calibrated the model to variable estimates from the literature. For the younger (older) cohort, the cost per fracture averted was $66,606 ($18,256), consistent with a validated Markov simulation model. The effect of a 1 percentage point change in vertebral efficacy was 24 (5) times the effect of a 1 percentage point change in persistence for the younger cohort when QALYs (fractures) were involved. Nonvertebral efficacy had approximately 27 (9) times the effect of persistence. For the older cohort, the ratios were 15 (4.5) and 33 (10) for vertebral and nonvertebral fractures, respectively. In evaluating the claim of enhanced persistence, formulary decision makers need to exercise caution to ensure that efficacy is not compromised. Two drugs would have to be virtually identical in efficacy for better persistence to improve cost-effectiveness.