Abstract
BACKGROUND: Because of the absence of biological parameters for fatigue, appropriate instruments for assessing the degree of fatigue are important in the diagnosis and management of people complaining of fatigue-like symptoms. This study statistically analyzed the fatigue scores from two typical questionnaire-based instruments: the Korean version of the Multidimensional Fatigue Inventory (MFI-K) and the modified Chalder Fatigue Scale (mKCFQ). METHODS: Seventy participants (males n = 40, females n = 30, median age 48 years old, range of 25-67) were grouped into three groups ('mild' = 20, 'moderate' = 42, and 'severe' = 8) according to self-reported fatigue levels using a 7-point Likert scale. The similarities and differences between two instrument-derived scores were analyzed using correlations (r) and multidimensional scaling (MDS). RESULTS: The total scores of the two assessments were significantly correlated (r = 75%, p < 0.001), as were the subscores ('Total Physical fatigue': r = 76%, p < 0.001, 'Total Mental fatigue': r = 56%, p < 0.001). Relative overestimation of the MFI-K (45.8 ± 11.3) compared to the mKCFQ (36.1 ± 16.2) was observed, which was especially prominent in the 'mild' group. The scores of the three groups were more easily distinguished by the mKCFQ than by the MFI-K. In terms of the five dimension scores, we found a higher correlation of the two assessments for 'general fatigue' (r = 79%, p < 0.001) and 'physical fatigue' (r = 66%, p < 0.001) than for the reductions in 'motivation' (r = 41%, p < 0.01) and 'activity' (r = 26%, p > 0.05). CONCLUSIONS: Our results may indicate the usefulness of the two instruments, especially for the physical symptoms of fatigue ('general' and 'physical' fatigue). Furthermore, the MFI-K may be useful for conditions of moderate-to-severe fatigue, such as chronic fatigue syndrome, but the mKCFQ may be useful for all spectra of fatigue, including in subhealthy people.