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OBJECTIVE: To examine the psychometric properties and construct validity of a self-administered Rheumatoid Arthritis Disease Activity Index (RADAI). METHODS: Five items of the Rapid Assessment of Disease Activity in Rheumatology (RADAR) questionnaire were aggregated into the RADAI and assessed for their factor loading, internal consistency, and construct validity. RESULTS: In 55 patients with RA, the RADAI had a high internal consistency (Cronbach's alpha = 0.91) and correlated with physician's assessment of disease activity (r = 0.54, P < 0.01), the swollen joint count (r = 0.54, P < 0.01), and the C-reactive protein value (r = 0.43, P < 0.01). CONCLUSION: The RADAI is a highly reliable and valid self-administered measure of disease activity for clinical, health services, and epidemiologic research. Its sensitivity to change in longitudinal studies needs further study.
Stucki et al. (Thu,) studied this question.