Background The Quality Adjusted Life Year (QALY), based on health-related quality of life measures such as euroqol 5 dimensions (EQ-5D), is an important outcome in rheumatoid arthritis (RA) studies, as it facilitates comparative analyses of cost-effectiveness. Identifying drivers of a gain in QALY would be helpful in predicting who may respond to a given treatment.
Objectives To investigate how each of the four DAS28 components are associated with the EULAR and EQ-5D responses, and what baseline variables that are predictive of the gain in QALY following one year of biological therapy.
Methods Clinical and patient-reported data were collected at baseline, three months, six months and one year in outpatients with RA initiating biological therapy in routine care. A cross-tabulation based on EULAR versus EQ-5D responses was performed, and the association of each of the four DAS28 components across the EULAR/EQ-5D response groups was tested. For EQ-5D, an improvement above the minimally important difference (MID) of 0.05 units (1) was considered a response. A moderate or good EULAR treatment response at one year was considered a EULAR response. Patients who withdrew from treatment were considered EULAR non-responders. Predictors of a gain in QALY were assessed in a multiple regression model including baseline clinical and patient-reported data as explanatory variables.
Results A total of 315 patients entered the study, 33 were lost to follow-up. Baseline characteristics: 77% women, 78% IgM rheumatoid factor positive, mean (SD) age: 55 (13) years, disease duration: 10 (9) years, DAS28: 5.0 (1.2), HAQ-score: 1.24 (0.70), EQ-5D: 0.59 (0.19).
Among each of the four DAS28 components, the patient global RA assessment on a visual analogue scale (VAS) was most strongly associated with both EULAR and EQ-5D responses. Thus, 5 of the 6 possible group comparisons were highly significant (p<0.0001), see Table.
Eighty % of the patients gained QALY after one year of biological therapy; their mean (SD) gain was 0.14 (0.13). The gain in QALY increased by 0.016 per cm of increase in baseline patient global RA assessment and 0.004 per baseline swollen joint increase, and patients with two or more extra-articular manifestations gained 0.106 more QALY’s compared with those without such manifestations.
Conclusions Among the four DAS28 components, the patient global RA assessment was most strongly associated with both EULAR and EQ-5D responses, and it was also a baseline predictor of the gain in QALY achieved after one year of therapy. As the four DAS28 components showed different characteristics, the components may need to be analyzed separately when used in cost-effectiveness studies.
Marra et al. A comparison of generic, indirect utility measures (the HUI2, HUI3, SF-6D, and the EQ-5D) and disease-specific instruments (the RAQoL and the HAQ) in rheumatoid arthritis. Soc Sci Med 2005 Apr;60(7):1571-82.
Disclosure of Interest None Declared
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