Cost-effectiveness of TNF inhibitors vs synthetic disease-modifying antirheumatic drugs in patients with rheumatoid arthritis: a Markov model study based on two longitudinal observational studies

Objective. The objective of this study was to estimate the additional costs and health benefits of adding a TNF inhibitor (TNFi) (adalimumab, certolizumab, etanercept, golimumab, infliximab) to a synthetic DMARD (sDMARD), e.g. MTX, in patients with RA. Methods. We developed the Norwegian RA model as a Markov model simulating 10 years of treatment with either TNFi plus sDMARDs (TNFi strategy) or sDMARDs alone (synthetic strategy). Patients in both strategies started in one of seven health states, based on the Short Form-6 Dimensions (SF-6D). The patients could move to better or worse health states according to transition probabilities. In the TNFi strategy, patients could stay on TNFi (including switch of TNFi), or switch to non-TNFi-biologics (abatacept, rituximab, tocilizumab), sDMARDs or no DMARD. In the synthetic strategy, patients remained on sDMARDs. Data from two observational studies were used for the assessment of resource use and utilities in the health states. Health benefits were evaluated using the EuroQol-5 Dimensions (EQ-5D) and SF-6D. Results. The Norwegian RA model predicted that 10-year discounted health care costs totalled (sic)124 942 ((sic)475 266 including production losses) for the TNFi strategy and (sic)65 584 ((sic)436 517) for the synthetic strategy. The cost per additionally gained quality-adjusted life-year of adding a TNFi was (sic)92 557 ((sic)60 227 including production losses) using SF-6D and (sic)61 285 ((sic)39 841) using EQ-5D. Including health care costs only, the probability that TNFi treatment was cost-effective was 90% when using EQ-5D, assuming a Norwegian willingness-to-pay level of (sic)67 300. Conclusion. TNFi treatment for RA is cost-effective when accounting for production losses. Excluding production losses, TNFi treatment is cost-effective using EQ-5D, but not SF-6D.