A modified rheumatoid arthritis disease activity score without acute-phase reactants (mDAS28) for epidemiological research
Graduate School of Biomedical Sciences, Clinical & Population Health Research Program; Department of Medicine, Division of Preventive and Behavorial Medicine
Medical Subject Headings
Acute-Phase Proteins; Arthritis, Rheumatoid; Cohort Studies; Cross-Sectional Studies; Female; Health Status; Humans; Joints; Male; Middle Aged; Predictive Value of Tests; Reproducibility of Results; Rheumatology; Severity of Illness Index
OBJECTIVE: To develop and validate a modified version of the Disease Activity Score with 28 joint count (mDAS28), for use in epidemiological research, when acute-phase reactant values are unavailable.
METHODS: In a cross-sectional development cohort (5729 patients), statistically significant predictors of the logarithm of erythrocyte sedimentation rate (lnESR) were identified. After computation of the mDAS28, a cross-sectional validation cohort (5578 patients) was used to evaluate internal, criterion, and construct validities. The ability of the mDAS28 to discriminate between disease states was also assessed. A second validation cohort (longitudinal, 336 pairs of patient visits) was used to assess sensitivity to change.
RESULTS: Significant predictors of lnESR included tender and swollen joints with 28 counts, patient's and physician's assessments of global health, and patient's assessment of pain (visual analog scale 0-100 mm) and a physical function (modified Health Assessment Questionnaire 0-3; mHAQ). Satisfactory internal validity (alpha = 0.72) and strong criterion validity compared to the DAS28, the Simplified Disease Activity Index (SDAI), and the Clinical Disease Activity Index (CDAI) (r = 0.87-0.96) were found. Predictive validity was demonstrated by good correlation with the mHAQ (r = 0.58). The mDAS28 showed substantial agreement with the DAS28, SDAI, and CDAI in discriminating between disease states (kappa = 0.70-0.77) and moderate to substantial agreement between response levels (kappa = 0.52-0.73). Both mDAS28 and DAS28 measures classified patients similarly in remission compared to the SDAI and CDAI. The mDAS28 was superior in detecting change (standardized response mean = 0.58) followed by the DAS28, CDAI, and SDAI.
CONCLUSION: The mDAS28 is a valid and sensitive tool to assess disease activity in epidemiological research, as an alternative to the DAS28, when acute-phase reactant values are unavailable.
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Citation: J Rheumatol. 2010 Aug 1;37(8):1607-14. Epub 2010 Jul 1. Link to article on publisher's website