A SELF-REPORT THOMPSON ARTICULAR INDEX - WHAT DOES IT MEASURE

The aim of this study was to investigate the reliability and validity of the self-report Thompson articular index (ThAI) in Dutch patients w ith rheumatoid arthritis (RA), A rheumatologist assessed the ThAI in 4 3 patients with RA. Patients completed the self-report ThAI and the AI MS-2 questionnaire to assess physical function, pain, mood and level o f tension. Blood samples were taken to measure the erythrocyte sedimen tation rate (ESR). After 4 weeks, patients were sent a questionnaire f or a repeat assessment of the self-report AI, The test-retest reliabil ity of the self-report ThAI was adequate (ICC = 0.83). There was low a greement between ThAI scores from patients and AI scores assessed by t he rheumatologist (ICC = 0.44). Self-report ThAI scores (mean = 230.5) were significantly higher than the rheumatologist's scores (mean = 11 0.8). Levels of agreement between patients and rheumatologist for indi vidual joints were disappointing, ranging from 49% to 74% (Cohen's kap pa from -0.02 to 0.48), The rheumatologist's ThAI scores correlated si gnificantly with ESR (r = 0.55) and physical function (r = 0.44), but not with pain, mood or level of tension. Patients' scores con-elated s ignificantly with physical function (r = 0.51), pain (r = 0.43), and m ood (r = 0.36) but not with ESR or level of tension. In regression ana lyses the only significant predictor of the rheumatologist's ThAI scor es was ESR, and for patients' scores physical function, thus showing t hat patients' responses are not confounded by mood or level of tension . In conclusion, the self-report ThAI is a reliable measure, but the v alidity is questionable because of the non-significant correlation wit h ESR and the low level of agreement between patients and rheumatologi st. The results indicate that self-reported joint involvement is more closely related to physical function than to arthritic activity.