Validation of an Italian version of the Arthritis Impact Measurement Scales 2 (ITALIAN-AIMS2) for patients with osteoarthritis of the knee

Objective. To validate a translated version of the revised and expanded Art hritis Impact Measurement Scales (AIMS2) to be used by Italian patients wit h osteoarthritis (OA) of the knee. Methods. The AIMS2 was translated into Italian and administered to a cohort of 178 outpatients with symptomatic OA of the knee who attended 12 partici pating rheumatological institutes in northern, central and southern Italy. A random sample of 71 patients were readministered the AIMS2, 7 days after the first visit, to evaluate the instrument's test-retest reliability. Afte r 6 months, the subjects were asked to return to the institutes for a secon d administration of the questionnaire. Results. The internal consistency reliability of each scale score, as estim ated by Cronbach's alpha coefficient, was high and indicated that the compo nents of the scale measured the same construct. The items all correlated wi th each other, but there was no redundancy; this indicates that each domain addressed a somewhat different aspect of functional disability. The test-r etest reliability equalled or exceeded 0.80 for eight of the 12 scales. Fac tor analysis provided a three-factor health status model explaining 63.5% o f the variance. Arthritis pain and psychological scale were loaded on the f irst factor, together with physical scales for mobility level and walking a nd bending. The upper limb function scales formed the second factor. The th ird factor was determined by the social dimension. These results demonstrat e that the physical health status scales of the AIMS2 are valid, as shown b y the significant, moderate to high correlations between the AIMS2 subscale s and the majority of the clinical measures. Conclusion. Our data suggest that, like the original questionnaire, the tra nslated version of AIMS2 is a reliable, consistent and valid instrument for measuring health status and physical functioning in patients with OA of th e knee.