The feeling of fatigue--fatigue severity by unidimensional versus composite questionnaires

The authors' purpose in this study was to compare the perception of fatigue severity as measured by different fatigue questionnaires. The authors evaluated 3 groups of patients in a cross-sectional study: chronic fatigue syndrome (CFS, n = 20), non-CFS fatigue (n = 20), and familial Mediterranean fever (FMF n = 25). In addition, the authors tracked 7 patients with CFS longitudinally for severity of fatigue. The severity of fatigue-related symptoms was assessed with 2 questionnaires: the unidimensional Chalder's Fatigue Severity Scale (CH) and the composite Fatigue Impact Scale (FI) which has 3 subscales--cognitive, physical, and social--and a total score. In the cross-sectional study, correlations between CH and FI cognitive scores were r = .78 (p < .0001), CH versus FI physical scores r = .603 (p < .0001), CH versus FI social scores r = .66 (p < .0001), and CH versus FI total scores r = .74 (p < .0001). In the longitudinal survey of CFS patients, the authors compared 30 questionnaires revealing correlations of CH versus FI cognitive scores r = .64 (p = .0004), CH versus FI physical r = .68 (p = .0001), CH versus FI social r = .87 (p < .0001), and CH versus FI total r = .90 (p < .0001). Fatigue severity as assessed by the unidimensional CH scale and the composite FI scale is comparable. The simple CH scale may be adequate for the assessment of the feeling of fatigue, in general, and for monitoring the severity of fatigue in CFS, in particular.