Validation of the International Classification of Functioning, Disability, and Health (ICF) Brief Core Set for osteoarthritis

OBJECTIVE: To validate the International Classification of Functioning, Disability, and Health (ICF) Brief Core Set for osteoarthritis (OA) by comparing the preliminary Brief Core Set to a selection of categories from the Comprehensive Core Set that explain most of the variance of functioning and health. METHODS: Patients with knee OA were asked to complete the Case Report Form for Patients, which includes the 36-item Short Form Health Survey (SF-36) and the Self-administered Comorbidity Questionnaire (SCQ). For each patient, the research staff was asked to complete the Case Report Form for Health Professionals, which includes the ICF Comprehensive Core Set for OA. Two individual questions regarding patients' general health and functioning were completed by both the patients and the research staff. The ICF categories to be entered into an initial regression model were selected following systematic steps in accordance with the ICF structure. Based on the initial models, additional models were generated by systematically substituting the ICF categories included in the initial models with other highly intercorrelated categories. RESULTS: A consecutive sample of 122 patients completed this study. Sixteen candidate ICF categories were identified by 15 linear regression models, which accounted for 5.5-57.7% of the total variance. Besides the two categories, b710 and b730, that are already included in the preliminary Brief Core Set, 14 additional categories were identified to be potential candidates for the Core Set. CONCLUSIONS: This study complemented the development of the Brief Core Set, which should be further refined by incorporating the opinions of patients, clinicians, and statisticians.