Evaluation of disease activity in rheumatoid arthritis by Routine Assessment of Patient Index Data 3 (RAPID3) and its correlation to Disease Activity Score 28 (DAS28) and Clinical Disease Activity Index (CDAI): an Indian experience

Serial objective assessment of disease activity in rheumatoid arthritis (RA) is imperative to achieve remission. Routine Assessment of Patient Index Data 3 (RAPID3), an index without formal joint counts, appears attractive for evaluation of disease activity in RA patients in a busy clinical setting. This study aims to evaluate correlation and agreement of RAPID3 with Disease Activity Score 28 (DAS28) and Clinical Disease Activity Index (CDAI) in RA patients. All patients completed a Multidimensional Health Assessment Questionnaire (MDHAQ) at each visit. A physician/assessor 28-joint count and erythrocyte sedimentation rate were completed in 200 literate patients with RA to score DAS28, CDAI, and RAPID3. RAPID3 includes the three MDHAQ patient self-report RA core dataset measures for physical function, pain, and patient global estimate. Proposed RAPID3 (range, 0–30) severity categories of high (>12), moderate (6.1–12.0), low (3.1–6.0), and near remission (≤3) were compared to DAS28 (0–10) activity categories of high (> 5.1), moderate (3.21–5.1), low (2.61–3.2), and remission (≤ 2.6), and CDAI (0–76) categories of >22, 10.1–22.0, 2.9–10.0, and ≤2.8. Statistical significance was analyzed using Spearman correlations, cross-tabulations, and kappa statistics. Comparison of RAPID3 with DAS28 and CDAI indicated Spearman rank-order correlation coefficients for DAS28 with RAPID3 of 0.910, and for CDAI with RAPID3 of 0.907, all highly significant (P < 0.001). There was substantial agreement between RAPID3 and DAS28 (kappa value = 0.634, P < 0.001) and also between RAPID3 and CDAI (kappa value = 0.690, P < 0.001). Overall, 89–94 % of patients who met DAS28 or CDAI moderate/high activity criteria met similar RAPID severity criteria and 84–88 % who met DAS28 or CDAI remission/low activity criteria also met similar RAPID criteria. RAPID3 scores provide similar quantitative information to DAS28 and CDAI, and hence, is an informative index for evaluation of disease activity in RA in busy clinical settings.