Interrater reliability of the extended ICF core set for stroke applied by physical therapists

The World Health Organization's International Classification of Functioning, Disability and Health (ICF) is gaining recognition in physical therapy. The Extended ICF Core Set for Stroke is a practical tool that represents a selection of categories from the whole classification and can be used along with the ICF qualifier scale to describe patients' functioning and disability following stroke. The application of the ICF qualifier scale poses the question of interrater reliability. The primary objective of this investigation was to study the agreement between physical therapists' ratings of subjects' functioning and disability with the Extended ICF Core Set for Stroke and with the ICF qualifier scale. Further objectives were to explore the relationships between agreement and rater confidence and between agreement and physical therapists' areas of core competence.

A monocentric, cross-sectional reliability study was conducted. A consecutive sample of 30 subjects after stroke participated. Two physical therapists rated the subjects' functioning in 166 ICF categories.

The interrater agreement of the 2 physical therapists was moderate across all judgments (observed agreement=51%, kappa=.41). Interrater reliability was not related to rater confidence or to the physical therapists' areas of core competence.

The present study suggests potential improvements to enhance the implementation of the ICF and the Extended ICF Core Set for Stroke in practice. The results hint at the importance of the operationalization of the ICF categories and the standardization of the rating process, which might be useful in controlling for rater effects and increasing reliability.