Abstract
Objective
To develop a continuous composite index of disease activity for rheumatoid arthritis (RA) based on the 7 American College of Rheumatology (ACR) core data set of disease activity measures: Mean Overall Index for Rheumatoid Arthritis (MOI-RA).
Methods
The MOI-RA is the mean of standardized values of tender and swollen joint counts (28, 42, or 66/68 joint counts), physical function (Health Assessment Questionnaire 0–3), patient’s and physician’s assessments of global health and patient’s assessment of pain (visual analog scale 0–100 mm) and erythrocyte sedimentation rate (1–100). All the 7 components were standardized (0–100), and the mean of standardized values was calculated. The range of MOI-RA is 0–100; higher values indicate poorer outcomes. The validity and measurement properties of MOI-RA were analyzed in 169 patients in the Finnish RA Combination therapy trial.
Results
The mean MOI-RA28 decreased from 38.5 to 13.3 [standardized response mean (SRM) = 1.8, effect size (ES) = 1.9] from baseline to 6 months, compared to Disease Activity Score (DAS) 28, which decreased from 5.55 to 2.77 (SRM = 2.0, ES = 2.8). Correlation between MOI-RA28 and DAS28 was 0.90. When compared to the ACR response categories (20/50/ACR remission), changes in MOI-RA versions (using 28/42/66 joints) were similar. The reproducibility of MOI-RA with different joint counts was 0.97. A simulation in which 15% of the component values of MOI-RA were randomly omitted indicated an intraclass correlation coefficient of 0.98 between incomplete and complete data.
Conclusion
MOI-RA is a simple and feasible index based on the ACR core data set of disease activity measures for assessment of disease activity and treatment response in RA trials and clinical settings.
Key Indexing Terms:Footnotes
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H. Mäkinen, MD; P. Hannonen, MD, PhD; T. Sokka, MD, PhD, Jyväskylä Central Hospital; H. Kautiainen, BA, Rheumatism Foundation Hospital.
- Accepted for publication January 24, 2008.
