Cross-cultural adaptation, validity, and reliability of the Persian version of the Upper Limb Functional Index

The Upper Limb Functional Index (ULFI) is a patient-reported outcome measure (PROM) designed to evaluate both the functional status and the level of participation in patients with upper limb musculoskeletal disorders (ULMSDs). The purpose of this study was translation, cross-cultural adaptation, and psychometric evaluation of the original ULFI into Persian (ULFI-Pr).

The original ULFI was translated into Persian through double forward and backward translations. Consecutive symptomatic upper limb patients (n = 180, male = 60%, age = 38.21 ± 7.13) were recruited and completed the ULFI-Pr and the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaires. Internal consistency and test-retest reliability were determined using Cronbach's Alpha and the Intra-class Correlation Coefficient (ICC_2.1). Criterion validity was analyzed by evaluating the Pearson's r correlation coefficient between the ULFI-Pr and DASH questionnaires. Construct validity was examined through exploratory factor analysis (EFA) using Maximum Likelihood Extraction with Promax rotation.

The original ULFI was translated and cross-culturally adapted into Persian with only minor wording changes. The ULFI-Pr demonstrated high levels of internal consistency (α = 0.91) and test-retest reliability (ICC_2.1=0.92). The correlation between the ULFI and DASH was high (r = 0.71). The EFA demonstrated a one-factor structure that explained 38.2% of total variance. No floor or ceiling effects were observed.

The ULFI-Pr can be considered as a region-specific, single-factor structure PROM for evaluation of patients with upper limb disorders for clinical and research purposes in Persian language populations.