The telephone-based application of the modified fatigue impact scale in individuals with multiple sclerosis: An investigation of measurement properties

Abstract

BackgroundFatigue is one of the most common symptoms reported by individuals with multiple sclerosis and it contributes to the reduction of the functionality. Therefore, it is important to assess the impact of fatigue on daily living of individuals with multiple sclerosis. The Modified Fatigue Impact Scale (MFIS) is an instrument to assess the perception of the impact of fatigue. However, there have been no investigations about the measurement properties of this instrument administered over the telephone for individuals with multiple sclerosis. ObjectivesTo verify the concurrent validity, the test-retest reliability, the standard error of measurement (SEM) and the minimal detectable change (MDC) of the MFIS applied over the telephone to assess the perception of the impact of fatigue of individuals with multiple sclerosis. MethodsThe MFIS, composed of 21 items covering three domains: physical, cognitive and psychosocial, was applied at three different moments with an interval of 5–7 days. To establish the concurrent criterion validity, the face-to-face application and the first evaluation by telephone were used. The two telephone assessments were used to assess the test-retest reliability The intraclass correlation coefficient (ICC) with 95 % confidence interval (CI) and the Bland-Altman method were used. The standard error of measurement (SEM) and the MDC was calculated according to reliability results. ResultsThirty individuals (40.83 ± 10.61, 60 % female) were included. The median score on the Expanded Disability Status Scale was 2.00 (±4.00). The majority of participants experienced fatigue (n = 17; 56.67 %). A significant and high magnitude correlation (0.70 ≤ ICC ≤ 0.87, p < 0.001) was found in the investigation of concurrent criterion validity. The Bland-Altman method showed a mean difference between 0.70 to 2.17 points between face-to-face and telephone-based application of the MFIS. For test-retest reliability, a significant and very high magnitude correlation (0.91 ≤ ICC ≤ 0.97, p < 0.001) was found. The Bland-Altman method showed a mean difference between -0.03 and -0.77 points between two telephone-based applications. The SEM and the MDC were 0.71 and 1.97 points. ConclusionThe telephone-based application of the MFIS to assess the perceived impact of fatigue in individuals with multiple sclerosis demonstrated adequate measurement properties, and may be a valuable tool to assess patients in clinical practice.