To develop a short form of the knee and hip osteoarthritis quality of life questionnaire, the Mini-OAKHQOL, preserving the conceptual model and, as far as possible, the content and the psychometric properties of the original instrument.
A two-step shortening procedure was used: (1) a consensus Delphi method, with a panel of patients and another of professionals independently asked to select items and (2) a nominal group, where patients, professionals, and methodologists reached consensus on the final selection of items, using information from the panels and from modern measurement and classical test theory analyses. The psychometric properties of the Mini-OAKHQOL were assessed in an independent population-based sample of 581 subjects with knee or hip osteoarthritis.
The two-step shortening procedure resulted in a 20-item questionnaire. Confirmatory factor analysis showed preservation of the original five-dimensional structure. Rasch analyses showed the unidimensionality and invariance by sex, age, and joint of the main dimensions. Convergent validity, reproducibility, and internal consistency were similar to or better than those of the original OAKHQOL.
The 20-item Mini-OAKHQOL has good psychometric properties and can be used for the measurement of quality of life in subjects with osteoarthritis of the lower limbs.