To validate a translated version of the revised and expanded Arthritis Impact Measurement Scales (AIMS2) to be used by Italian patients with osteoarthritis (OA) of the knee.
The AIMS2 was translated into Italian and administered to a cohort of 178 outpatients with symptomatic OA of the knee who attended 12 participating 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. After 6 months, the subjects were asked to return to the institutes for a second administration of the questionnaire.
The internal consistency reliability of each scale score, as estimated by Cronbach's alpha coefficient, was high and indicated that the components of the scale measured the same construct. The items all correlated with each other, but there was no redundancy; this indicates that each domain addressed a somewhat different aspect of functional disability. The test-retest reliability equalled or exceeded 0.80 for eight of the 12 scales. Factor analysis provided a three-factor health status model explaining 63.5% of the variance. Arthritis pain and psychological scale were loaded on the first factor, together with physical scales for mobility level and walking and bending. The upper limb function scales formed the second factor. The third factor was determined by the social dimension. These results demonstrate that the physical health status scales of the AIMS2 are valid, as shown by the significant, moderate to high correlations between the AIMS2 subscales and the majority of the clinical measures.
Our data suggest that, like the original questionnaire, the translated version of AIMS2 is a reliable, consistent and valid instrument for measuring health status and physical functioning in patients with OA of the knee.