Psychometric study of Turkish version of Fatigue Impact Scale in multiple sclerosis patients

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Abstract

Background

The aims of this study were to test the validity, test–retest reliability, and internal consistency of Turkish version of FIS; the variables affecting FIS score.

Materials and methods

71 MS patients and 68 healthy subjects were included to the study.

Results

Total FIS score and subscale scores were different statistically between MS patients and healthy volunteers in both first and second FIS applications (p < 0.001). These results showed that FIS is validated in divergent direction. BDI score was higher in MS patients than healthy volunteers (p < 0.001). There was no statistically significant difference between two study groups for cognitive subscale scores, after the effect of depression was eliminated (p > 0.05). To assess the test–retest reliability, the scores of two FIS applications did not differ statistically (cognitive t = 1.948 p > 0.05, physical t = 1.420 p = 0.160, social t = 1.470 p = 0.146, total t = 1.990 p = 0.05). Intraclass correlation coefficients were 0.89 (99% confidence interval: 0.79–0.94) for cognitive, 0.95 (0.91–0.97) for physical, 0.91 (0.83–0.95) for social, and 0.93 (0.86–0.96) for total FIS scores (p < 0.001). EDSS correlated with physical subscores in both applications of FIS.

Conclusion

Turkish version of FIS, which is valid and reliable, seems an appropriate tool for the assessment of the effects of fatigue in Turkish MS population.

Introduction

The most common and disabling symptom in multiple sclerosis (MS) is severe fatigue, present in 65 to 97% of MS patients [1], [2], [3], [4], [5], [6]. Fatigue induced by MS is different from those seen in healthy people [7]. It is unique to the disorder and is not just an extreme form of the “tiredness” but rather a “short-circuiting” type of fatigue which is incompatible with the activities performed. 15–40% of MS patients complain fatigue as a disabling problem that causes mainly physical, social, and cognitive incapacity as well as unemployment [8], [9], [10].

In order to evaluate the multidimensional aspect of fatigue, several scales have been developed. Fatigue Impact Scale (FIS) (Fisk et al., 1994) is a commonly used fatigue scale in both clinical and experimental studies [11].

We planned to test the validity, test–retest reliability, and internal consistency of Turkish version of FIS; the variables affecting FIS score.

Section snippets

Fatigue Impact Scale

FIS is a multidimensional scale measuring the physical, cognitive, and social effects of fatigue. It comprises 40 questions, of which 10 related to cognitive, 10 to physical, and 20 to social subscales. Each question scores between 1 and 4, changing from minimal to severe degrees. The maximum total score is 160.

We defined the level of patients’ disability using Expanded Disability Status Scale (EDSS) [12] before the application of FIS. Additionally, Beck Depression Inventory (BDI), was applied

Results

The demographic and clinical characteristics of MS patients and healthy volunteers were given in Table 1. There was no statistically significant difference between two groups regarding age, gender, and education level, but marital status was different between groups.

Total FIS score and physical and social subscale scores were different statistically between MS patients and healthy volunteers in both first and second FIS applications (p < 0.001). Although cognitive subscale scores were similar in

Discussion

FIS is a multidimensional scale for the measurement of the effects of fatigue on the daily life activities and quality of life of MS patients. Although it was shortened from 40 questions for practical reasons, we planned to validate the original version of the scale in this study. German and Swedish versions of FIS were developed before [15], [16].

In our study, MS patients and healthy volunteers were different regarding marital status. Being a divorcee or single may affect the psychological

Conclusion

In this validation study of FIS, the most remarkable differences had been found also in social and physical subscales. The cognitive subscale differed the least. However our results showed that FIS is validated in divergent direction. After the effect of depression was eliminated, FIS total, physical, and social subscale scores were still significantly high in MS patients. There was no valid cognitive subscale, when the effect of depression was eliminated.

High Cronbach's alpha values indicate

Acknowledgments

We are gratefully indebted to all of the participants in this study, who so willingly shared their life experiences of MS-related fatigue with us. We are also grateful to the staff working within the MED-ILAC.

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