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OBJECTIVE: To evaluate the Disease Activity Score (DAS) using various aggregated dimensions to quantify treatment outcome in patients with rheumatoid arthritis (RA), in order to determine the best instrument to be used as an endpoint that indicates good response in terms of EULAR response criteria and DAS28 remission criteria, and which satisfies the demands of clinical rheumatology. METHODS: Using raw data for each patient subjected to anti-tumor necrosis factor-a therapy (81 patients), before and 6 months after treatment, DAS28 was calculated 4 times using the standard equation, as follows: (1) DAS 1 (the standard DAS28): tender joint count (TJC), swollen joint count (SJC), patient global assessment (PGA), erythrocyte sedimentation rate (ESR); (2) DAS 2: TJC, SJC, PGA, C-reactive protein (CRP); (3) DAS 3: TJC, SJC, physician global assessment (PhGA), ESR; and (4) DAS 4: TJC, SJC, PhGA, CRP. Disease activity was identified if DAS score exceeded 5.1. A clinically significant response was recorded if there had been improvement of > 1.2 of the DAS score. RESULTS: DAS 2, DAS3, and DAS4 were superior to the current DAS score used for assessment of RA activity (effect size differences were -0.35, -0.13, and -0.48, respectively). Assessment of disease activity using TJC, SJC, PhGA, and CRP was the best tool to assess response to therapy. ESR was marginally superior to CRP in its sensitivity to monitor disease activity changes (effect sizes 1.08 and 1.03, respectively). CONCLUSION: These results suggest that self-report indices on their own, such as PGA and pain score, are inadequate indicators of disease activity. The DAS might profitably be amended by one or 2 continuous measures for better quantification of the degree of improvement of patients on a given therapeutic modality. Using PhGA and CRP instead of PGA and ESR, respectively, in the DAS equation discriminated better between different patients' responses than the traditional DAS score.