The patient-specific functional scale:: Validity in workers' compensation claimants

Objective: To examine the construct and predictive validity of the Patient-Specific Functional Scale (PSFS) in workers' compensation claimants. Design: Prospective cohort study with 1-year follow-up. Setting: A workers' compensation rehabilitation facility. Participants: Subjects included 294 claimants with a variety of musculoskeletal disorders. The sample was predominantly male (70%), with a mean age of 44 years. Subjects completed a battery of measures at baseline including the PSFS, the Pain Disability Index (PDI), and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). Interventions: Not applicable. Main Outcome Measures: Outcomes for determining predictive validity included administrative indicators of timely return to work and recovery during the 1-year follow-up. Analysis included Pearson correlation and multivariable Cox and logistic regression. Results: At baseline, the PSFS correlated moderately (r range, 0.3-0.5) with other indicators of functional limitation (PDI, SF-36 role-physical subscale) but negligibly with the SF-36 mental health and role-emotional subscales. The PSFS was associated with timely recovery (adjusted hazard ratio, 1.16; 95% confidence interval, 1.07-1.27) with increasing functional limitation related to delayed recovery. Conclusions: Results provide construct and predictive validity evidence for the PSFS as an indicator of functional limitation in workers' compensation claimants.