Mapping Patient-Specific Functional Scale (PSFS) Items to the International Classification of Functioning, Disability and Health (ICF)

Background. The International Classification of Functioning, Disability and Health (ICF) provides a common framework for clinical outcome measurement. Because the Patient-Specific Functional Scale (PSFS) is widely used for documenting change over time in individual patients receiving musculoskeletal physical therapy, investigation of the extent to which PSFS items reflect the ICF is needed. Objective. The study objective was to investigate the extent to which patient-generated PSFS items reflect ICF domains. Design. This investigation was an observational content validity study. Methods. A total of 2,911 PSFS items from 1,050 files for patients with musculoskeletal disorders were analyzed. The data were from a random sample of participants in the Otago Outcome Measures Project at 4 clinics of the School of Physiotherapy, University of Otago, situated in 3 New Zealand cities. Patient-nominated PSFS items were categorized and mapped with thematic analysis techniques to ICF components, chapters, and categories. Subgroup analyses were conducted for body region of injury and age ranges. Results. All (100%) of the analyzed items could be mapped to the ICF. Most patient-nominated items mapped to the activity component (80.0%), some items mapped to the participation component (7.7%), other items were related to impairment (7.4%), and the fourth group contained items that overlapped the activity and participation components (4.9%). Similar results were found for each of the 5 body regions and across age ranges in subgroup analyses. Limitations. These results are limited to individual patients seeking musculoskeletal physical therapy. Patient-generated PSFS items were investigated. Conclusions. The ICF activity component was most commonly represented by patient-nominated PSFS items, the participation component was moderately represented, and impairment was least represented. Hence, the PSFS would complement impairment-based clinical outcome measures.