Pain in RA is multifaceted and complex. Measuring instruments are inadequate. Rheumatoid Arthritis Pain Scale (RAPS) (Arthritis Care Res 45:317-323, 2001) was designed to measure pain comprehensively but has been sparsely reported. We decided to validate a suitable version for our community. Post translation (contextual), RAPS was administered (face to face interview) to 172 consenting patients of moderately severe RA (mean pain visual analogue scale (VAS) 5.4 cm) in a cross-sectional study using standard rheumatology case record form. RAPS contained 24 questions (numeric score, anchored at 0 (never) and 6 (always); range 0-144). Fifty-seven cohort patients on supervised rheumatology care were followed for 16 weeks. SPSS (v16) was used for statistical analysis, significant p < 0.05. RAPS showed good face and content validity (consensus). Construct/criterion validity was demonstrated for subclass domains and total RAPS (Cronbach's alpha 0.91, test-retest interclass correlation (Pearson) 0.71). Fair to modest correlation (p < 0.05) was seen with swollen joint count (0.16), Indian health assessment questionnaire (0.23), medical outcome short form (SF), 36 physical score (-0.35), SF 36 mental score (-0.21) and C-reactive protein (0.25), not with pain VAS. Similar results were shown for subclass domains (physiologic, affective, sensory, cognitive), except low alpha for affective. Age, disease duration and SF 36 were significant predictors (linear regression). In factor analysis, RAPS loaded with SF 36. The standardized response mean (0.6) was equal to pain VAS and DAS 28. RAPS was found to be a valid and clinically relevant instrument for measuring pain in Indian patients suffering from RA. It merits more widespread clinical use.
Keywords: Methodology; Pain; Rheumatic diseases; Rheumatoid arthritis (RA); Specialty fields; Validation of measures—PROs.