The Fatigue Descriptive Scale (FDS): a useful tool to evaluate fatigue in multiple sclerosis

Although fatigue is common among multiple sclerosis (MS) patients, evaluation of this symptom is difficult due to the subjectivity and variability of the complaint. We proposed the Fatigue Descriptive Scale (FDS) as a tool to evaluate the severity and quality of fatigue in a group of patients suffering from MS. As a way to demonstrate the usefulness of this scale we applied the FDS in a group of 155 patients (105 women and 50 men) with clinically-definite multiple sclerosis, as outlined according to Poser's criteria. Age was 36.2 +/- 11.1 years (range 12-62) and time of evolution was 8.3 +/- 9.4 years (range 1-44). The Fatigue Severity Scale (FSS) was also used. Descriptive statistics techniques and techniques for nonparametric distribution (Spearman Rank, Kruskal-Wallis ANOVA) were used. One hundred and eighteen patients reported fatigue (73 spontaneously, 45 when questioned). All descriptions of fatigue were ranked according to FDS categories. Eighty-five patients defined the symptom as fatigue with exercise, 26 as asthenia and seven as the worsening of other symptoms. Fatigue by itself produced limited or disrupted activity in 78 patients; work-related functions were limited in 48 patients; social relations were limited in 29 patients; and self-care difficult for one patient. Fifty-six patients suffered fatigue daily. FDS score was 4.9 +/- 3.9 (range 0-13). FSS was 3.1 +/- 1.7 (range 0.2-6.6). FDS and FSS of Krupp were highly correlated (R = 0.87, p < 0.001). Therefore, in comparison with other scales, the FDS shows remarkable usefulness in classifying, periodicity, and severity of fatigue in MS patients. The high correlation with the FSS implies that it is a valid method to measure the severity of fatigue, as was demonstrated in our paper proposing the FDS. The importance of this new scale is its ability to inform the clinicians in a very quick, easy, and at the same time complete way, how severe the fatigue really is and how it affects the patient.