Health economics and its measures in rheumatoid arthritis
Abstract: Objectives: To study: (I) the impact on cost-utility analyses of applying different national EuroQol 5-Dimensions (EQ-5D) preference sets; (II and III) whether, in methotrexate-refractory, early rheumatoid arthritis (RA), the addition of infliximab results in superior health-related quality of life (HRQoL) and may be considered cost-effective, as compared to adding sulfasalazine and hydroxychloroquine; (IV) how costs relate to disability (measured by the health-assessment questionnaire, HAQ), disease activity (28-joint disease activity score, DAS28) and HRQoL (EQ-5D) in RA. Methods: In the observational SSATG register, one-year quality-adjusted life-year (QALY) accumulation of two interventions was compared according to the UK, US, or Danish EQ-5D preference sets. Two-year QALY accumulation and incremental cost-effectiveness were compared between the treament arms of the SWEFOT trial, randomising methotrexate-refractory, early RA patients to addition of infliximab or sulfasalazine and hydroxychloroquine. Linking SSATG data to register-derived costs of anti-rheumatic drugs, patient care, and work loss, the associations of HAQ, DAS28, and EQ-5D scores to costs were compared by correlation and regression analyses. Results: Applying the UK, rather than the US or Danish preference sets, resulted in a 50% higher incremental QALY estimate. In the SWEFOT trial, no significant between-group differences were seen regarding QALY accumulation or work loss costs, while drug and healthcare costs were higher in the infliximab arm, resulting in very high incremental cost-effectiveness ratios for the infliximab strategy. Regardless of analysis method, societal RA costs were more closely related to HAQ than DAS28 or EQ-5D scores. Conclusions: Results of cost-utility analyses may vary depending on the national EQ-5D preference set used. In the SWEFOT trial, similar HRQoL effects were observed in both treatment arms, and the infliximab strategy was not cost-effective over two years. HAQ disability was a better marker of RA costs than DAS28 disease activity or EQ-5D HRQoL.
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