To estimate minimal clinically important improvement (MCII) of RAPID-3 (Routine Assessment of Patient Index Data 3) in rheumatoid arthritis (RA).
RAPID-3 was computed before and after treatment escalation in a prospective study of adults with active RA. Patient judgment of improvement was used as the standard for a receiver-operating characteristic curve, from which MCII was estimated.
Mean RAPID-3 improved from 16.3 to 11.1 between visits. MCII was -3.8 based on simultaneously optimized sensitivity and specificity, -3.5 using the 0.80 specificity criterion, and -4.1 using the Youden index.
RAPID-3 improvement of 3.8/30 units appears clinically meaningful.