Modified disease activity scores that include twenty-eight-joint counts. Development and validation in a prospective longitudinal study of patients with rheumatoid arthritis.

OBJECTIVE The development and validation of Modified Disease Activity Scores (DAS) that include different 28-joint counts. METHODS These scores were developed by canonical discriminant analyses and validated for criterion, correlational, and construct validity. The influence of disease duration on the composition of the DAS was also investigated. RESULTS No influence of disease duration was found. The Modified DAS that included 28-joint counts were able to discriminate between high and low disease activity (as indicated by clinical decisions of rheumatologists). CONCLUSION The Modified DAS are as valid as disease activity scores that include more comprehensive joint counts.