Cross cultural adaptation and psychometric evaluation of an Arabic version of the modified fatigue impact scale in people with multiple sclerosis

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Cross Cultural Adaptation and Psychometric evaluation of an Arabic version of the Modified Fatigue Impact Scale in People with Multiple Sclerosis

Hanan Khalil PhD Assocaite Professorproject administrationconceptualizationmethodologydata collectiondata anay Alham Al-Shorman PhD Assisstant Professorconceptualizationdata collectiondata anaylisiswritting-up , Alia A. Alghwiri PhD Associate professor , Nour Abdo PhD Assistant Professorconceptualizationdata analysiswriting-up , Khalid El-Salem MDFAAN Professor of neurologyconceptualizationrecruitmentmethodologywriting up , Sarah Shalabi Bsc conceptualizationdata collectionwriting up , Aseel Aburub M.Sc. conceptualizationdata collectiondata analysis and writing up and editing PII: DOI: Reference:

S2211-0348(19)30950-2 https://doi.org/10.1016/j.msard.2019.101878 MSARD 101878

To appear in:

Multiple Sclerosis and Related Disorders

Received date: Revised date: Accepted date:

26 February 2019 11 November 2019 28 November 2019

Please cite this article as: Hanan Khalil PhD Assocaite Professorproject administrationconceptualizationmethodolog Alham Al-Shorman PhD Assisstant Professorconceptualizationdata collectiondata anaylisiswritting-up , Alia A. Alghwiri PhD Associate professor , Nour Abdo PhD Assistant Professorconceptualizationdata analysiswritin Khalid El-Salem MDFAAN Professor of neurologyconceptualizationrecruitmentmethodologywriting up , Sarah Shalabi Bsc conceptualizationdata collectionwriting up , Aseel Aburub M.Sc. conceptualizationdata collectio Cross Cultural Adaptation and Psychometric evaluation of an Arabic version of the Modified Fatigue Impact Scale in People with Multiple Sclerosis, Multiple Sclerosis and Related Disorders (2019), doi: https://doi.org/10.1016/j.msard.2019.101878

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Highlights   

The Arabic Modified Fatigue Impact scale (A-MFIS) has two factors cognitive and physical. The A-MFIS has high concurrent validity with measures of disease severity and quality of life. The A-MFIS subscale and total scores have high test-retest reliability.

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Title: Cross Cultural Adaptation and Psychometric evaluation of an Arabic version of the Modified Fatigue Impact Scale in People with Multiple Sclerosis Hanan Khalil, PhD Assocaite Professor Jordan University of Science and Technology Faculty of Applied Medical Sciences, Department of Rehabilitation Sciences, Irbid, Jordan Alham Al-Shorman, PhD Assisstant Professor Jordan University of Science and Technology Faculty of Applied Medical Sciences, Department of Rehabilitation Sciences, Irbid, Jordan Alia A. Alghwiri, PhD Associate professor The University of Jordan, School of Rehabilitation Sciences, Amman, Jordan Nour Abdo, PhD Assistant Professor Jordan University of Science and Technology Faculty of Medicine, Department of Public Health, Irbid, Jordan Khalid El-Salem, MD, FAAN Professor of neurology Jordan University of Science and Technology Faculty of Medicine, Department of Neurosciences, Irbid, Jordan

Sarah Shalabi, Bsc Jordan University of Science and Technology Faculty of Applied Medical Sciences, Department of Rehabilitation Sciences, Irbid, Jordan Aseel Aburub, M.Sc. School of Health and Rehabilitation, Keele University, Newcastle Under Lyme, United Kingdom *Address all correspondence to Dr. Hanan Khalil, Department of Rehabilitation Sciences, Faculty of Applied Medical Sciences, Jordan University of Science and Technology, Irbid 22110, Jordan. Email:[email protected]. Phone number: 00962797713017

Key words: Modified fatigue scale, Arabic version, reliability, validity, multiple sclerosis

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Abstract Background: Fatigue is a common symptom in multiple sclerosis and has significant impacts on participation and quality of life. Thus, fatigue assessment in this population is always a necessity. Objectives: to examine the underlying structure, validity and test-retest reliability of an Arabic translated and culturally adapted version of the Modified Fatigue Impact scale (A-MFIS). Methods: The study was carried out into two phases: firstly, the English version of the MFIS was translated into Arabic and secondly, a detailed analysis of the psychometric properties and the structure of the translated version was conducted using Principle Component Analysis (PCA). Convergent validity was assessed by comparison with measures of disease severity, quality of life and with another measure of fatigue. Test retest reliability was assessed with intraclass correlations. Results: 145 subjects participated in the study. The PCA revealed that the instrument has two main factors ―cognitive‖ and ―physical‖, rather than the original three factors scale. Significant correlations were found between the A-MFIS and measures of disease severity and quality of life (P<0.05). Furthermore, the A-MFIS subscale and total scores have good to high test-retest reliability. Conclusion: The A-MFIS has high reliability and concurrent validity with other measures of disease severity and quality of life.

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Introduction Fatigue is one of one of the most common symptoms of multiple sclerosis (MS), reported to affect between 50% and 80% of MS patients at some point in the disease course 1, 2. Fatigue is a subjective symptom that has multidimensional character. Although for this reason assessing fatigue is complex 2, it is usually estimated by self-report scales in which people are asked to describe and rate their fatigue, and/ or rate experiences related to the impact of fatigue on their daily life2. The most commonly used scales for assessing fatigue in MS are the Fatigue Severity Scale (FSS) and the Modified Fatigue Impact Scale (MFIS). Both scales are reliable and valid in assessing short-term perceived fatigue (i.e. within the last month of assessment) 3-5. However, the FSS was found to be moderately reliable in long term fatigue assessment in people with MS; on the other hand, the MFIS was found to be highly reliable in long-term fatigue assessment (i.e. over six months)6. Besides, the MS council recommended the 21-item Modified Fatigue Impact Scale (MFIS) for use in clinical practice and research 7. The MFIS 8 is a shortened version of the 40-item Fatigue Impact scale 9 which offers a multidimensional assessment of the effects of fatigue in terms of physical, cognitive, and psychosocial functioning. In addition to its multidimensional features, the MFIS has good psychometric properties for use in people with MS 10, 11, correlates well with the FSS 10 and takes shorter time to administer than the original 40item version. However, The MFIS has been also criticised in term of its structure 12, 13. For example, Mill et al (2010) 12 reported that the items in the MFIS‘s domains need to be restructured, and Larson et. al (2013) 13 recommended conducting further studies to assess the structure of the MFIS. The increased number of international research as well as the diversity of populations and cultures around the world has created the need to validate self-reported instruments in groups

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different from those originally used to develop the measure. Within this context, the MFIS which was originally developed in English language has been translated into different languages 14, 15 1622

. However, to our knowledge, the MFIS has not yet been translated into Arabic language

whether the standard Arabic language or any other Arabic delicate. Throughout the world, Arabic is the native language of between 242 million people23. Moreover, Arabic has been adopted as one of the official languages of the World Health Organization (WHO), along with Spanish, English, Chinese, French, and Russian 24. While a majority of Arabic speaking healthcare professionals have a basic understanding of written English, self-reported tools such as the MFIS cannot be administered to the Arab population without validating the tool in Arabic language. The only Arabic translated scale assessing fatigue in MS is the FSS, which examine the short-term fatigue state 6. Overall, fatigue in people with MS is known to be associated with a decreased quality of life on several life indices including lower employment rates, decreased daily function, and sleep disturbances 2, 25. Fatigue may worsen the progression of the disease and previous work has found that it is associated with disease severity measured using the EDSS 26-28. The current study aimed to translate the MFIS into the standard Arabic language through the process of crosscultural adaptation, and explore the psychometric properties of the produced Arabic version (AMFIS) among a sample of Arabic-speaking people with MS. The specific aims were to 1) examine the underlying structure of the A-MFIS; 2) determine the floor and ceiling effects; 3) determine the convergent validity of the A-MFIS with the EDSS, quality of life and another measure of fatigue severity; 4) determine the reliability of the A-MFIS. Method

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Participants: The data for this study obtained as part of baseline data of three ongoing studies at Jordan University of Science and Technology and the University of Jordan. Overall, participants were recruited from two hospitals in Jordan: King Abdulla University Hospital (Irbid, Jordan) as well as Al-Basheer hospital (Amman, Jordan). Sequential MS patients attending routine neurology clinic appointments at these two hospitals between December 2016 and October 2018 were screened for eligibility by a neurology consultant. Eligible subjects were invited to participate in the study. Brochures and adverts about the study were also distributed through the Jordanian Multiple Sclerosis Society. Participants who were willing to participate were also screened for eligibility by a neurology consultant. Inclusion criteria were: 1) neurologist-confirmed diagnosis of MS according to the revised McDonald criteria 29; 2) no exacerbation of symptoms 30 days prior to completing testing; 2) ability to walk independently with or without walking aid outdoor for at least 10 metres ; 3) ability to read and understand Arabic; 4) age ≥ 18 years; 5) capacity to give informed consent. Exclusion criteria were: 1) presence of additional neurological disorders that may affect fatigue or mobility (e.g. head injury, stroke, vestibular dysfunction, or peripheral neuropathy); and 2) presence of severe cognitive deficits or behavioural disorders preventing participation. Procedure: The study was carried out into two phases: firstly, the English version of the MFIS was translated into Arabic in accordance with the World Health Organization (WHO) guideline for translating assessment tool30 and secondly, a detailed analysis of the psychometric properties of the translated version of the MFIS was conducted. Participants were assessed in two different locations (School of Rehabilitation Sciences at the University of Jordan at Amman, and Department of Rehabilitation Sciences, Jordan University of Science and Technology at Irbid, Jordan) depending on their residence area. In both sites, participants were assessed by the

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same investigator. All participants gave a written informed consent approved from the Institutional Research Committees of Jordan University of Science and Technology (HK20140194, AS-20150182 and AA-20/2012–2013). Translation and cross-cultural adaptation: According to the National Multiple Sclerosis Society, the MFIS is in the public domain and no permission was required for the translation process. Forward translation of the English version of the MFIS into Arabic was carried out by two independent bilingual translators, whose first language was Arabic. The study panel revised the two versions of the forward translations in which discrepancies were discussed and reconciled; thus, a synthesized version of the Arabic MFIS (A-MFIS) was agreed upon. The synthesized version of the A-MFIS was then back translated into English by an independent bilingual translator whose first language is English. Linguistic discrepancies in the back translation were discussed and resolved by the study panel. To ensure accuracy of meanings and that all questions are understood by individuals, the pre-final version of the A-MFIS was pilot tested on five MS patients. Feedback from patients and translators were discussed by the study panel in which the final version of the A-MFIS was issued. Psychometric evaluation: In order to address the third goal of the study, it was hypothesized that A-MFIS would have moderate negative correlation with health-related quality of life measures and positive moderate correlation with the EDSS score and fatigue severity. In order to test this, the convergent validity of the A-MFIS was assessed by testing the assumption that if the A-MFIS is valid then it should converge (i.e. correlate) with other tests that measure a similar constructs 32. This means that in the presence of a higher score on A-MFIS (an indication of a higher level of fatigue), one may expect a poorer performance on health-related quality of life for example. Thus, in this study the A-MFIS was administered simultaneously with measures

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of health-related quality of life, disease severity and a previously validated measure of fatigue severity. The Arabic-version of the FSS

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was used to assess fatigue in only 45 participants of

the sample. The Arabic Short Form-36 (SF36; V1)33 and the Kurtzke Expanded Disability Status Scale (EDSS) were used to evaluate health-related quality of life and disease severity, respectively. The scores from the vitality subscales of the SF36 as well as the physical and mental summary components were used for data analysis. All tests were administered in a standardized manner. The order of tests for each participant was randomized (between participants) to minimize any bias due to order effects 33. To evaluate test- retest reliability of the A-MFIS, subsample of the existing participants completed the A-MFIS in a second session which was scheduled after a week. Overall, all participants who completed the first session of assessment were invited to participate in the retest session which was conducted one week after. The sub-sample represents those participants who agreed and attended the second session. The 1-week gap was considered between sessions to minimize the probability of a recall bias33. The same examiner was involved in both sessions. Demographic data including age and gender were recorded. Duration of diseases was noted and EDSS was scored by two neurologists; one neurologist completed the EDSS scoring for participants who were recruited from KAUH, irbid and one conducted the EDSS scoring for participants who were recruited from Al-Basheer hospital, Amman. Both neurologists had previous training on conducting the EDSS assessments as per standard operating procedure and both have extensive exeprience in assessing and treating patients with MS. Statistical analysis: Descriptive statistics were calculated for all variables. Data was checked for normality using histograms (Statistical Package for the Social Sciences (SPSS) Version 21 (SPSS, Chicago)). To investigate the underlying structure of the A-MFIS, the

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responses of the total sample were subjected to a principal factor analysis and principal component analysis, using the R Statistical Package R64 3.4.1). The factor-analysis procedure identified different factors of fatigue and provided an estimate of each factor loading. Several solutions of scree tests were examined to identify the optimal number of factors to be retained including the Kaiser‘s eigenvalue-greater-than-one rule, Parallel Analysis and Optimal Coordinate (OC) and Acceleration Factor (AF) 30. Both the OC and AF outperform the Kaiser‘s eigenvalue-greater-than-one rule since they are more robust to abrupt changes to the slope of curve 30. This multiple approach is recommended to confirm the optimal number of factors by avoiding the bias of over or under estimating the required number of factors 30. Varimax orthogonal rotation was then used to reorganize the representation of items for each factor selected. This was also confirmed by the variables factor map of principal component analysis (PCA) 34, 35. The floor-effect (percentage of patients who scored at floor level, equivalent to the 10% lowest scores on the scale); and the ceiling-effect (percentage of patients who scored at the ceiling level, that corresponded to 10% highest scores on the scale) 36 were calculated for each domain of the A-MFIS. To test convergent validity of the A-MFIS, its correlations with clinical tests of fatigue severity, disease severity and health-related quality of life were computed using Spearman‘s correlation coefficients. A spearman correlation coefficient of ≥0.7 indicates strong correlation, 0.4 to 0.6 indicates moderate correlation, and 0.10 to 0.3 indicates weak correlation37. To evaluate test-retest reliability of the A-MFIS, a paired t-test using the test and re-test scores was used to evaluate if there were any systematic differences between the 2 session scores. The intra-class correlation coefficients (ICC) were calculated to assess both systematic

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and random error that may affect relative test- retest reliability. The ICC (2,1) (the 2 way random model of consistency) 38 was used because final scores on the A-MFIS were based on a single trial. An ICC of >0.75 indicates ―excellent‖ reliability, 0.40 to 0.74 indicates ―fair to good‖ reliability, and <0.40 indicates ―poor‖ reliability 38. The internal consistency of the A-MFIS was evaluated with Cronbach‘s alpha. An α coefficient greater than 0.7 was considered satisfactory 39

. Measures of absolute reliability were expressed as the standard error of measurement

(SEM) and the minimal detectable change at the 95% confidence level (MDC 95) 40. The standard error of measurement (SEM) was estimated from the square root of the mean error term from a repeated measure ANOVA 40. The MDC95 was calculated as 1.96*√2*SEM. Thus, the MDC95 values provide information about the confidence limits associated with measurement error so that, for example, it can be stated with 95% confidence that an individual‘s change score that exceeds the MDC represents a true change.

Results Translation and cultural adaptation of the A-MFIS On conducting the translation process, it was important to prioritize the conceptual correspondence and cultural relevance over accurate word-for- word translation. Every attempt was taken to keep the idea conveyed by the question taken into consideration its relevance to Arabic people at the same time. The translation and cultural adaptation process highlighted the difficulty in word-for word translation at some items. For example, in the phrase ―I am more clumsy and uncoordinated‖, there is not an Arabic equivalence to ―clumsy‖. Similarly, the direct translation

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of ―my muscles feel much weaker than they should‖ suggests, in Arabic, that strength is decreased. Again, in the phrase ―I have had to pace myself in physical activities‖, a direct translation to the word ―pace‖ into Arabic will make the meaning of the phrase abstruse. In all these cases and other similar cases, an appropriate and culturally relevant substitute was used considering to keep the conceptual equivalency.

Psychometric evaluation of the A-MFIS One hundred forty-five individuals with MS participated in the study (male/female; 50/95). Table 1 shows the characteristics of the participants. The A-MFIS was completed by all participants with scores ranging from 0 to 84 (mean = 40.14, SD = 20.0289).

A factor-analysis provided different solutions with one, two, or four factors could be retained (Figure 1). The two-factor solution was consistently identified using the Parallel analysis and Optimal Coordinates approaches. Furthermore, the results of the principal component analysis and Varimax rotation for the two-factor analysis confirmed retaining twofactors (Table 2, Figure 2 & Figure 3). Finally, 52% of the variance was explained by the twofactor instrument which we selected; the 52% represents the cumulative percentage of variance which is a source of disagreement in the factor analysis approach. The first-factor, ‗cognitive dimension‘, was similar to the original questionnaire (10 items). The second-factor, which we called ‗physical dimension‘ was composed of 11 items. The two-items from the ―psychosocial‖ dimension factor in the original Modified Fatigue Impact Scale were loaded on the physical dimension (Table 2, Figure 2 & Figure 3). Internal consistency was high; Cronbach‘s alpha for the total score, cognitive and physical subscales were 0.94, 91 and 0.91 respectively. 11



The total A-MFIS score and the cognitive and physical subscales did not show any ceiling or floor effect (Table 3), with 6.89% of the sample size scored on the lowest 10% of the scores and 3.45% scores in the top 10% of the score. Significant moderate to large correlations were found between the A-MFIS-total score and the measures of SF-36 (PCS), SF-36 (MCS), and SF-36 (Vitality), the FSS and the EDSS (P<0.05) (Table 4).

Test-retest reliability was conducted in a subsample (n=62) of those who completed day 1 assessment. Table 5 shows the first and second testing days‘ descriptive scores as well as the differences between the scores obtained from the 2 days. The mean score of the A-MFIS-total for day 1 was 40.18 ± 20.44 and 41.10 ± 20.52 for day 2. No significant differences were observed between the A-MFIS-subscales' scores and the A-MFIS-total score between the 2 visits (Table 5). Table 6 illustrates the ICCs, the standard error of measurements (SEM) and the minimal detectable change (MDC95). The intra-class correlation coefficient reflected high agreement for the A-MFIS-total score (ICC=0.95) (Table 6).

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Discussion To our knowledge, this is the first study to translate the MFIS to standard Arabic language that can be used with any Arabic-speaking individual around the world and to establish the psychometric properties of the A-MFIS in Arabic-speaking people with MS. The A-MFIS was translated in the general Arabic language that can be understood by all Arabic speaking people. This could have a positive impact in healthcare globally, because Arabic is considered the sixth most spoken language 41. Additionally, the National Health Services (NHS) in the UK addressed Arabic as one of the languages that are needed to be covered for information about the most common diseases such as low back pain, diabetes, women health, and heart diseases42. However, very few outcome measures have been translated in validated to Arabic language, specifically for multiple sclerosis. Thus, this study might add an important value in assessing fatigue in people with MS. According to the findings of the present study, the A-MFIS is a valid and reliable tool for the assessment of fatigue in MS individuals. However, some questions should be raised regarding the structural validity of the MFIS. The major concern refers to the three-dimensional model proposed previously 17. Our factor analysis confirmed the multidimensional structure, but did not confirm the number of the factors. The principal component analysis in our study suggested the retain of only two factors in which items number 8 and 9 of the MFIS were assigned to the physical domain, rather than the psychosocial domain. This is consistent with previous observations and it might be explained by the small number (i.e., 2) of items in the psychosocial domain. Our results are similar to those reported in the four European countries study by Kos, et.al (2005) 17 in which items 8 and 9 were also loaded into the physical domain, in

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people with MS. Similarly, a study investigated the validity of the MFIS in people with Parkinson‘s revealed that after running factor analysis for the three original subscales, items number 8 and 9 were added to the physical subscale, ending with two subscales (physical and cognitive), rather than the original structure (cognitive, psychosocial and physical) 43. The explanation of assigning these items (items no.8 & 9) to the physical domain might be because of the nature of the items. Since these items ―motivated to participate in social activities‖, and ―ability to do things away from home‖ might interfere with the physical abilities of participants to perform the tasks. Convergent validity of the A-MFIS was evaluated by comparing the subscale and total scores of the A-MFIS with disease severity and health-related quality of life measures. While conducting this study, Al-Sobayel et al published an article for translation, validity and reliability of an Arabic version of the FSS 31. Thus, we have collected the Arabic FSS, and checked the validity of the A-MFIS with the rest of the sample (n=45), and it was not feasible to repeat all the sample that has been already collected before their publication. Interestingly, moderate correlation (r=0.44) between the total A-MFIS and the FSS, confirming that the A-MFIS is a valid tool for assessing fatigue in MS. Although the total score of the A-MFIS was moderately correlated with the physical, mental and vitality domains of the SF-36, and the FSS, but it was weakly correlated with the EDSS score. A study conducted in four European countries reported similar findings with the translated versions of the MFIS which were not correlated with the EDSS. This might be explained by a recent population-based study that investigated relationship between fatigue and sociodemographic variables, which reported a high correlation of fatigue with age and disease severity, but only among patients with primary progressive MS, and our inclusion criteria was limited to people with relapsing remitting MS.

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The test-retest reliability of the A-MFIS is higher than what was reported by the original MFIS (ICC=0.86) 11 and other languages of the MFIS such as the Dutch version (ICC=0.85) 15 and the European versions of the MFIS (Belgian, Italian, Slovenian or Spanish version) that had ICC values ranged between 084 and 0.93 17. Additionally, the MDC95 score of the subscales though were close to what were reported in the original MFIS 11, the MDC95 for the A-MFIStotal score was much lower than the MDC95 for the MFIS-total score in English (MDC95=20.2) 11 language. Such differences in these studies may be due to the variability of time interval between test and retest administrations. For example, the test-retest reliability of the original MFIS was assessed over a period of 6 months 11. Such interval may indicate true change in their fatigue status rather than lower agreement score in the measure. In our study, the test-retest reliability of the A-MFIS was assessed only in 62 participants. It was not feasible for the rest of the sample to perform the test again, due to work/ personal commitments. This study is not without limitations. Firstly, an evaluation of the responsiveness of the A-MFIS was not performed. Secondly, the test-retest reliability was performed in a sub-sample which was relatively small. This limits our ability to generalize the results reported here to the MS population in general. Although two back translations are recommended 43, the WHO guideline for translating assessment tool 24 indicates that one back translation is sufficient. For the purposes of this study, the recruitment of a second translator was difficult as bilingual translators whose first language is English are very few in Jordan. Thus, the back translation was made only by one independent bilingual translator. In conclusion, this study shows that Arabic version of the MFIS is valid tool to assess fatigue in MS population. Furthermore, the A-MFIS subscale and total scores have good to high

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test-retest reliability. The MFIS has the advantage that it is a multidimensional scale which covers physical and cognitive domains.

Financial disclosure/conflict of interest related to the submitted manuscript:The authors report no conflicts of interest. Acknowledgment: The authors would like to acknowledge all the participants of the study. Acknowledgement for funding support is to Jordan University of Science and Technology (Grant number 0194/2014 to HK) as well as the University of Jordan (AA-20/2012–2013).

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Figure 1: Principal component analysis of scree tests

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Figure 2: Variables Factor Map of Principle Component Analysis.

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Figure 3: Principal component analysis

Items in red represent those belong to the physical dimension in the original scale. Items in green represent those belong to the psychosocial dimension in the original scale. These items loaded here in factor 1. Items in blue represent those belong to the cognitive dimension in the original scale loaded here in factor 2.

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Table 1: Descriptive of demographics (n=145) Outcome Age (years) Duration of disease (years)

EDSS (unit)

Range

Mean

SD

18 -59

36.6

10.2

1-30

8.4

5.5

Range

Median

1.0-6.5

3.0

Interquartile range 2.75

Duration of disease: years since date of diagnosis EDSS: Expanded Disability Status Scale

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Table 2: Principal factor analysis with varimax rotation I

Description

Factor

tem

Cog nitive

Physi cal

1

Alertness

0.58

0.16

2

Attention

0.76

0.2

3

Clear thinking

0.72

0.2

4

Coordination

0.14

0.62

5

Forgetfulness

0.46

0.30

6

Pace physical activities

0.23

0.48

7

Motivation-physical

0.30

0.66

8

Motivation-social

0.25

0.58

9

Outside activities

0.21

0.58

1

Maintain physical effort

0.19

0.75

1

Decision-making

0.65

0.35

1

Motivation-mental

0.73

0.29

1

Muscle weakness

0.21

0.70

1

Physically uncomfortable

0.29

0.67

0

1

2

3

4

23

1

Mental task completion

0.69

0.31

1

Thought organization

0.70

0.33

1

Physical task completion

0.27

0.70

1

Slow thinking

0.74

0.29

1

Concentration

0.71

0.35

2

Physical activities

0.35

0.63

2

Need for rest

0.36

0.67

5

6

7

8

9

0

1 Loading in bold represents the factors to which the items are assigned.

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Table 3: Floor and Ceiling results of the A-MFIS (n=145) Mean (SD)

A-MFIS Total A_MFIS (cognitive)

40.16

Range Definition

0.0-84

Definition

Floor

Ceiling

of Floor

of Ceiling

Effect

Effect (%)

Effect*

Effect**

(%)

8.4

75.6

6.89%

3.45%

4

36

14.58%

4.86%

4.3

39.6

6.94%

3.47%

(20.02) 17.50

0.0-40

(10.93)

A-MFIS

22.69

(physical)

(11.59)

0.0-44

*Floor effect is equivalent to the 10% worst possible results of the scale; **Ceiling effect is equivalent to the 10% best possible results of the scale (Bennett, 2002). The instrument is considered to have floor or ceiling effect if the floor effect percentage or the ceiling effect percentage were >15% of the sample size 46.

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Table 4: Correlations between A-MFIS subscales and measures of fatigue, disease severity and health-related quality of life A-MFIS-

A-MFIS-

A-MFIS-

Cognitive

Physical

Total

r

-0.34

-0.28

-0.50

P- value

0.00

0.00

0.00

r

-0.52

-0.49

-0.55

P- value

0.00

0.00

0.00

r

-0.41

-0.51

-0.52

P- value

0.00

0.00

0.00

r

0.16

0.32

0.25

P- value

0.06

0.00

0.00

r

0.39

0.36

0.44

P- value

0.01

0.01

0.00

SF-36 N=145 (PCS) SF-36 N=145 (MCS) SF-36 N=145 (Vitality)

EDSS

N=145

FSS N=45 (n=45)

r: Pearson correlation coefficient A-MFIS: Arabic Modified Fatigue Impact Scale SF-36 (PCS): Physical Component Summary score of the SF-36 SF-36 (MCS): Mental Component Summary score of the SF-36 FSS: Fatigue Severity Scale

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Table 5: Descriptive data for test retest reliability (n=62) Outcome

Day 1

Day 2

Differences between day 1 and day 2

Mean ± SD

Mean ± SD

Mean ± SD

P-value

A-MFIS-Total

40.18 ± 20.44

41.10 ± 20.52

-0.92 ± 8.6

0.405

A-MFIS (cognitive)

17.50 ± 10.93

17.03 ± 11.09

.468 ± 4.96

0.46

A-MFIS (physical)

22.69 ± 11.59

24.06 ± 11.79

-1.37 ± 6.92

0.12

A-MFIS: Arabic Modified Fatigue Impact Scale/ range from 0 to 84 with a higher score indicating a poorer performance Physical subscale of the A-MFIS ranges from 0 to 44 Cognitive subscale of the A-MFIS ranges from 0 to 40

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Table 6: Intra Class Correlation Coefficients (ICCs) for test re-test reliability, standard error of measurements (SEM) and minimal detectable changes (MDC95) for A-MIFS (n=62) Outcome

Cronbach’s

ICC

SEM

MDC95

Alpha A-MFIS-Total

0.93

0.95

6.13

6.86

A-MFIS (cognitive)

0.91

0.94

3.51

5.19

A-MFIS (physical)

0.91

0.90

4.89

6.13

A-MFIS: Arabic Modified Fatigue Impact Scale

28

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Authors contributions section: Hanan Khalil: project administration, conceptualization, methodology, data collection, data anaylisis, writting-up and editing; Alham Al-Shorman: conceptualization, data collection, data anaylisis, writting-up; Nour Abdo: conceptualization, data analysis, writing-up; Khalid ElSalem: conceptualization, recruitment, methodology, writing up; Sarah Shalabi: conceptualization, data collection, writing up; Aseel Aburub: conceptualization, data collection, data analysis and writing up and editing.

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