Structural Validity of the Arabic Upper Extremity Functional Index Using Exploratory and Confirmatory Factor Analysis

Abstract

The upper extremity functional index (UEFI) is a commonly used patient-reported outcome measure with good measurement properties. The Arabic UEFI has been reported to have sufficient reliability and construct validity, but its structural validity has not been examined yet. The aim of this study was to examine the structural validity of the Arabic UEFI using both exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) in patients with upper extremity musculoskeletal disorders. Participants with upper extremity musculoskeletal disorders attending physical therapy clinics were recruited. Participants were asked at their initial visit to physical therapy to complete the Arabic versions of the UEFI, and the numeric pain rating scale. In the EFA, the number of factors was determined using parallel analysis and maximum likelihood was used for extraction. The fit of the structural model identified using EFA was examined using CFA with multiple fit indices. The results of the EFA suggested one factor structure accounting for 57.22% of the total variance. All the UEFI items showed substantial loadings on the single factor that ranged from 0.51 to 0.85. The CFA multiple fit indices did not support the fit of the unidimensional structure at the first run of the analysis. Adding error covariance to items of similar function led to good fit of the data to the modified unidimensional model; χ2 = 665.94 (df = 162, P < 0.001), χ2/df = 2.88, Tucker–Lewis index (TLI) = 0.91, comparative fit index (CFI) = 0.92, root mean square error of approximation (RMSEA) = 0.086 (90% CI = 0.077-0.095), and standardized root mean residual (SRMR) = 0.045. The results of the EFA supported this unidimensional structure of the UEFI while the CFA supported this unidimensional structure after accounting for possible response dependency among some of the items. Clinicians and researchers can use one total score for the Arabic UEFI that reflects the level of upper extremity function.