Qualitative and quantitative assessment of fatigue in multiple sclerosis (MS)

It was the aim of the present study to develop a synoptic multidimensional test system for assessment of fatigue in multiple sclerosis (MS) patients objectifying physical and mental fatigue as well as the subjective and objective standpoint in these two fatigue forms. Seventy nine patients with relapsing remitting multiple sclerosis (RRMS) and 51 age-matched healthy controls (H) were analysed by means of the physical fatigue test (hand dynamometer) and an objective mental fatigue test (vigilance test from the computerised Test Battery for Attentional Performance). Furthermore, subjective tiredness caused by test procedures, subjective persisting tiredness (Modified Fatigue Impact Scale; MFIS: physical and cognitive scale) and mood (Beck Depression Inventory; BDI-18) were analysed. MS patients differed significantly from the controls in their objective physical and mental performance under fatigue, as well as in their subjective estimation of tiredness. MS patients showed an inverse relationship between below-average objective performance and high subjective feeling of tiredness when compared to controls. Subjectively severely tired MS patients achieved clearly poorer performances on the hand dynamometer test and slightly poorer performances on the vigilance test when compared to subjectively rarely tired MS patients. Depressed MS patients estimated their subjective tiredness in the MFIS significantly higher than non-depressed MS patients, but attained the same objective performance. This set of standardised tests enables meaningful comparisons between objective fatigue performance and subjective fatigue estimations in the physical and mental sphere and considers the influence of depression. Depression affects the subjective tiredness but not the objective fatigue performance.