Patient-reported outcomes in Asia: evaluation of the properties of the Rheumatoid Arthritis Impact of Disease (RAID) score in multiethnic Asian patients with rheumatoid arthritis

Patient-reported outcomes (PROs) such as the Europe-developed Rheumatoid Arthritis Impact of Disease (RAID) are important to assess patients' quality of life. Their interpretation may be culture-dependent. To evaluate the potential utility of RAID in multiethnic Asian rheumatoid arthritis (RA) patients. Cross-sectional study of English-speaking RA patients in a Singapore tertiary center. Validity of RAID (scored between 0 and 10 with higher score indicating worse status) was assessed by Spearman's correlation with patient global assessment (PGA), DAS28 and short form 12 (SF-12). Consistency was assessed by Cronbach's alpha and test-retest reliability by intra-class correlation coefficient (ICC) 7 days after (n = 20). Feasibility was assessed by % of missing data. Eighty-two patients were analyzed: median age 53 years (Q1:Q3 44.7; 60.7), disease duration 4.2 years (1.4; 8.8), 66 (81%) women and 54 (66%) Chinese. Although RA was moderately active (median DAS28, 3.2 (2.5; 4.3)), RAID score was very low (median, 1.9 (0.6; 3.7)) with 44 (53.7%) patients having RAID score between 0 and 2. RAID was strongly correlated with PGA (r = 0.75), and moderately with other outcomes (DAS28 r = 0.46, SF12 physical r = -0.45 and SF12 mental r = -0.52, p < 0.0001 for all). Consistency was high (Cronbach's alpha = 0.91). Test-retest reliability was excellent; ICC = 0.84 (95% confidence interval 0.74-0.90). Feasibility was good with only 2 patients with missing data. Despite considerable floor effects, the RAID appeared to be a valid and practical PRO to assess the impact of RA in Asia. Multiethnic Asian patients may underestimate the impact of their disease compared to European patients.