Psychometric properties of an International Classification of Functioning, Disability and Health (ICF)-oriented, adaptive questionnaire for the assessment of mobility, self-care and domestic life.

OBJECTIVE: Development of an adaptive, International Classification of Functioning, Disability and Health (ICF)-oriented patient questionnaire on mobility and self-care based on an item response theory model (MOSES questionnaire). METHODS: Using item reconstruction rules, items were developed for the ICF chapters "mobility", "self-care" and "domestic life". The resulting instrument, together with other instruments (SF-36, Short Musculoskeletal Function Assessment Questionnaire (SMFA), MacNew, Functional Independence Measure (FIM), Barthel) was presented to 549 patients with musculoskeletal disease, 212 patients with cardiac disease and 258 neurological rehabilitation patients in rehabilitation clinics in Germany. RESULTS: The MOSES questionnaire includes 58 items on 12 scales and fulfills the requirements of the 1-parameter item response theory model (Rasch model). The results indicate good reliability and high construct validity and sensitivity to change of the instrument. In the construction and selection of items, ICF contents that include complex processes of evaluation, and which presuppose skills that are not acquired prior to the individual learning process, were omitted due to a lack of unidimensionality. CONCLUSION: The successful implementation of the concept of applying rules to ICF categories in formulating the items of a patient questionnaire showed that the goal of a theory-driven measurement of activities using the ICF is feasible. The results of the project also raise questions as to the homogeneity of the contents of some ICF categories.