Reliability, measurement error, and validity of the Arabic version of the Patient-Specific Functional Scale in patients with upper extremity musculoskeletal disorders.

Abstract

To evaluate the measurement properties of the Arabic Patient-Specific Functional Scale (PSFS) in individuals with upper extremity musculoskeletal disorders. Participants with upper extremity musculoskeletal disorders (<i>N</i> = 139) completed the PSFS, Upper Extremity Functional Index (UEFI), the Disabilities of the Arm, Shoulder and Hand (DASH), Numeric Pain Rating Scale (NPRS) and the Global Assessment of Function scale (GAF). The same outcome measures were completed again with one week in addition to the Global Rating of Change Scale. The test-retest reliability, measurement error, floor and ceiling effects, and construct validity of the PSFS were examined. The PSFS demonstrated very good test-retest reliability (ICC_2,1 = 0.82; 95% CI: 0.71-0.88), with no evidence of floor or ceiling effects. The standard error of measurement was determined to be 0.74 while the minimal detectable change was 1.73 points. The PSFS demonstrated significant negative correlation with DASH, NPRS (-0.58, -0.35), and significant positive correlation with the UEFI and GAF (0.56, 0.50). The PSFS demonstrated statistically higher correlation with the DASH and UEFI compared with the NPRS (<i>p</i> < 0.004) supporting our predefined construct validity hypotheses. The Arabic PSFS is an applicable, reliable, and valid outcome measure of upper-extremity activity limitations for patients with upper extremity musculoskeletal disorders.