To explore whether it is possible to construct clinical measures of functioning by integrating information obtained across the categories of the International Classification of Functioning, Disability, and Health (ICF) using the ICF Core Set of osteoarthritis (OA) as a case in point.
Psychometric study using data from 437 patients with OA from Germany, Italy, Hungary, Serbia, and Singapore. The analyses were performed with the ICF categories of the comprehensive ICF Core Set for OA addressing functioning and using the Rasch model for ordered response options.
A clinical measure with 74 country-specific and seven common ICF categories was created with the pooled data of all countries but Hungary. The overall fit statistic according to the chi(2) was chi(df=405)(2)=451.73, P=0.054, and the Z-fit statistic was Z(mean)=-0.041 (Z(standard deviation [SD])=1.01) for items and Z(mean)=-0.15 (Z(SD)=1.19) for persons. The Person Separation Index r(beta) was 0.92.
For the first time, a cross-cultural clinical measure of functioning was constructed which integrates ICF categories. The results of this investigation are promising and can contribute to the acceptance and usefulness of the ICF in clinical practice.