Psychometric Evaluation of the Fatigue Severity Scale in Chronic Neck Pain.

This study aimed to evaluate the psychometric properties of the existing Turkish version of the Fatigue Severity Scale (FSS-TR) in individuals with chronic neck pain. A cross-sectional study. A total of 106 participants were included. Content validity was assessed by experts using the Item-Level Content Validity Index (I-CVI) and Content Validity Ratio, while face validity was examined through patient feedback using the Comprehensibility Index (CI). Construct validity was tested using Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA). CFA showed excellent fit indices (Comparative Fit Index = 0.989, Tucker-Lewis Index = 0.983, Root Mean Square Error of Approximation = 0.066, Standardized Root Mean Square Residual = 0.022), with factor loadings from 0.771 to 0.927. Convergent and discriminant validity were examined with Pearson correlations using the Turkish Fatigue Impact Scale (FIS-TR) and the Visual Analog Scale for fatigue (VAS fatigue), showing strong correlations with FIS-TR (r = 0.800, p < .001) and VAS fatigue (r = 0.803 and p < .001). Reliability analyses indicated excellent internal consistency (Cronbach's α = 0.959) and high test-retest reliability (ICC = 0.894). The findings suggest that the FSS-TR is a valid and reliable tool for assessing fatigue in individuals with CNP.