Investigating the dimension functioning from a condition-specific perspective and the qualifier scale of the International Classification of Functioning, Disability, and Health based on Rasch analyses.

Objective: This study aimed to explore to what extent the data collected for patients with low back pain, breast cancer, and stroke, based on the International Classification of Functioning, Disability and Health (ICF) Checklist, reflect the hypothesized single latent dimension functioning and whether the ICF qualifier scale expresses a clearly defined ordered sequence of response options. Design: Data including ratings of 56 ICF categories for low back pain, 54 for breast cancer, and 84 for stroke were analyzed using the Rasch model. Results: For each health condition, most of the ICF categories fit the Rasch model. In most of them, one or two of the four threshold estimates were reversed before collapsing the response options. The collapsing strategy 01122 was proposed. Conclusions: The fit residual statistics showed that most of the ICF categories selected for each of the health conditions reflect the single latent variable functioning. The ordering of the ICF qualifier scale was not consistent with the intended order.