To establish the responsiveness of observational and self-report methods for the assessment of disability in mobility in patients with osteoarthritis (OA).
Data from 186 patients with hip OA or knee OA were used. Data from 1 observational method and 4 self-report methods for the assessment of disability in mobility were collected at week 0 and again 12 weeks later. Using correlations and factor analysis, the relationships among changes in these 5 methods were established.
Intercorrelations between change scores of the self-report methods ranged from 0.12 to 0.34. Correlations between the observational method and the self-report methods ranged from 0.14 to 0.26. In the factor analysis, both the self-report methods and the observational method loaded on the same factor.
In a longitudinal design, no evidence for differential responsiveness of observational and self-report methods was obtained. Because of the advantages of questionnaires (they are easier to use, less time-consuming, and less of a burden to subjects), this implies that the use of self-report methods is to be preferred over observational methods.