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The impact of a revised EQ-5D population scoring on preference-based utility scores in an inflammatory arthritis cohort.Adams, Roisin; Craig, Benjamin M; Walsh, Cathal D; Veale, Douglas J; Bresnihan, Barry; FitzGerald, Oliver; Barry, Michael; National Centre for Pharmacoeconomics, St. James Hospital, Dublin, Ireland., email@example.com (2012-02-01)BACKGROUND AND OBJECTIVE: It is well established that there are problems with the EQ-5D. This is due to the original scoring methods used and how negative time trade-off (TTO) values were treated. A revised scoring method has been published. This article applies this to an inflammatory arthritis cohort. The objective is to examine the impact of a revised scoring system for the EQ-5D (UK) TTO on the utility estimates and in the case of rheumatoid arthritis, to explore the impact of using different utility metrics on the incremental cost-effectiveness ratio (ICER) results of an economic model. METHODS: A total of 504 patients with inflammatory arthritis were rescored using revised EQ-5D scoring, which uses an episodic random utility model to deal with negative TTO values. Differences in utility scores were compared and the new mapping coefficients were obtained. These were then used in an economic model to examine the impact on the ICER. RESULTS: In rheumatoid arthritis, the overall change is less for the revised EQ-5D scoring than with the original EQ-5D (TTO) but greater than the SF-6D: EQ-5D UK -0.22 (95% confidence interval [CI] -0.30 to -0.15), revised EQ-5D UK -0.16 (95% CI -0.21 to -0.10) and SF-6D -0.08 (95% CI -0.11 to -0.05). A similar trend is seen in the psoriatic arthritis group. The economic model produced different ICERs, when different utility measures were used; EQ-5D (TTO) euro42,402, SF-6D euro111,788, and revised EQ-5D (TTO) euro57,747. CONCLUSION: In the context of inflammatory arthritis, this article demonstrates that a revised scoring for EQ-5D may have a significant impact on utility estimates and on the output of the economic model.
Understanding the relationship between the EQ-5D, SF-6D, HAQ and disease activity in inflammatory arthritis.Adams, Roisin; Walsh, Cathal; Veale, Douglas; Bresnihan, Barry; FitzGerald, Oliver; Barry, Michael; National Centre for Pharmacoeconomics, St. James' Hospital, Dublin 8, Ireland., firstname.lastname@example.org (2012-02-01)BACKGROUND: The growth of economic analyses and in particular cost-utility analyses (CUA), which use the QALY as a measure of outcome, has heightened the interest in the methodologies used to calculate the QALY. The EQ-5D has produced quite different utility values from that of the SF-6D. This article seeks to understand these differences using a cohort of patients with inflammatory arthritis. OBJECTIVE: To examine the relationship between the disease-specific measure, Health Assessment Questionnaire (HAQ) disability index (DI) and the preference-based measures, SF-6D, EQ-5D and European League Against Arthritis (EULAR) Disease Activity Score (DAS) in patients with rheumatoid arthritis (RA) and psoriatic arthritis (PsA). METHODS: Patients with RA and PsA (n = 504) attending a tertiary rheumatology referral centre completed the HAQ, SF-6D and the EQ-5D before starting biological therapy and again 12 months later. The SF-36 was converted into a utility using the preference-based SF-6D. Clinical outcomes such as the DAS, joint counts and laboratory measures were also recorded. We calculated single index utility scores from the preference-based instruments using UK population norms. We used regression analysis to derive a mapping function and calculated utility scores from the HAQDI and the DAS 28. RESULTS: The mean utility observed at baseline for RA was 0.43 for the EQ-5D and 0.54 for the SF-6D and for PsA was 0.49 for the EQ-5D and 0.57 for the SF-6D. The utility gain demonstrated by the EQ-5D was over twice that of the SF-6D. The EQ-5D scored 17% of the RA group as less than 0 (state defined as worse than death); 7% of this group remained less than 0 at follow-up. The distribution of the utility estimates was similar for both RA and PsA. CONCLUSIONS: Our findings draw attention to the impact of states worse than death on the overall distribution for the EQ-5D derived utilities and how these impact on its use in practice. EQ-5D-derived QALY changes are over twice that of the SF-6D. The implication of this for decision makers is that cost-effectiveness evaluations for treatments in this disease class are likely to be very sensitive to the choice of utility measure.