Measuring fatigue in haemodialysis patients: psychometric properties of the Chalder Fatigue Questionnaire (CFQ)

Abstract

Background: Fatigue is common in haemodialysis (HD) patients, leading to poorer quality of life and patient outcomes. Given the complex and subjective nature of fatigue, and its overlap with sleep disturbances and depression, its measurement represents a challenge. Great variability exists in fatigue instruments used in this patient population, with little informed agreement on what scale would be optimal. Our aim was to evaluate the psychometric properties of the 11-item Chalder Fatigue Questionnaire (CFQ) in HD patients, including an assessment of the validity of the factor structure, internal-reliability, and discriminant validity with respect to psychological distress and comorbidity. Methods: Data were evaluated for psychometric analysis from a published study investigating clinical and psychosocial correlates of fatigue among 174 HD patients. Confirmatory factor analysis was used to determine the factor structure using Weighted Least-Squares with Mean and Variance adjustment (WLSMV) estimation. Findings: Mental and physical fatigue factors correlated highly (r=.70, p<.01) suggesting it is difficult to differentiate such symptoms. A bi-factor model, consisting of one general fatigue factor and two smaller factors (mental and physical fatigue), had good fit (CFI>.95; TLI>.95). The CFQ had high internal consistency and showed a moderate correlation with distress and a small association with comorbidity. Discussion: The CFQ can be summed to a total fatigue severity score, representing a composite of physical and mental fatigue, and has good psychometric properties. Taking into consideration its good psychometric properties and brief length, the CFQ should be used in future studies interested in measuring fatigue in HD patients.