Validity and reliability of the Swedish version of the Patient Specific Functional Scale in patients treated surgically for carpometacarpal joint osteoarthritis

Design: Cross-sectional clinical measurements. Introduction: Activity limitation is often persistent after surgically treated carpometacarpal (CMC) joint osteoarthritis (OA). Purpose: To describe content and concurrent validity, test-retest reliability and internal consistency of the Swedish version of the Patient Specific Functional Scale (PSFS) in patients with surgically treated CMC joint OA. Methods: Fifty-eight patients were assessed ten weeks after surgical treatment of CMC joint OA. PSFS, the shorter version of Disabilities of the Arm, Shoulder and Hand (Quick DASH), EuroQol-5Dimensions (EQ-5D), pain intensity, joint movement of CMC joint, grip and pinch strength were assessed. Classification of activities was done according to the International Classification of Functioning, Disability and Health (ICF). Spearman correlation, intra-class correlation coefficient (ICC) and Kappa were calculated to assess validity, test-retest reliability and internal consistency. The PSFS was administered twice, 2-3 days apart. Results: All of the activity limitations stated in the PSFS could be classified according to the activity component in the ICF. Significant correlations for the PSFS were obtained with pain at rest (r(s) = -0.36) and the Quick DASH (r(s) = -0.28). Test-retest reliability was good, ICC (0.79) and the three items of the PSFS correlated 0.69-0.83 with the total score of PSFS. Conclusion: Content validity was excellent, concurrent validity was low-moderate, as in earlier studies. The PSFS could be a valuable supplement to existing measures in measuring activity limitations in individuals with surgically treated CMC joint OA.