Validity and reliability of the EULAR instrument RAID.7 as a tool to assess individual domains of impact of disease in rheumatoid arthritis: a cross-sectional study of 671 patients

OBJECTIVE: The rheumatoid arthritis impact of disease (RAID) questionnaire comprises seven patient-important domains of disease impact (pain, function, fatigue, sleep disturbance, emotional well-being, physical well-being, coping). RAID was validated as a pooled-weighted score. Its seven individual items separately could provide a valuable tool in clinical practice to guide interventions targeting the patient’s experience of the disease. The aim was to separately assess the psychometric properties of each of the seven numeric rating scale (NRS) of the RAID (RAID.7). MATERIAL AND METHODS: Post hoc analyses of data from the cross-sectional RAID study and from the Rainbow study, an open-label 12-week trial of etanercept in patients with RA. Construct validity of each NRS was assessed cross-sectionally in the RAID data set by Spearman’s correlation with the respective external instrument of reference. Using the rainbow data set, we assessed reliability through intraclass correlation coefficient between the screening and the baseline visits and responsiveness (sensitivity to change) by standardised response mean between baseline and 12 weeks. RESULTS: A total of 671 patients with RA with features of established disease were analysed, 563 and 108 from RAID and Rainbow, respectively. The NRS correlated moderately to strongly with the respective external instrument of reference (r=0.62–0.81). Reliability ranged from 0.64 (0.51–0.74) (pain) to 0.83 (0.76–0.88) (sleep disturbance) and responsiveness from 0.93 (0.73–1.13) (sleep disturbance) to 1.34 (1.01–1.64) (pain). CONCLUSION: The separate use of the individual NRS of RAID (RAID.7) is valid, feasible, reliable and sensitive to change, representing an opportunity to improve the assessment and treatment of disease impact with minimal questionnaire burden. TRIAL REGISTRATION NUMBER: NCT00768053.