Psychometric properties of an Arabic translation of the modified fatigue impact scale in patients with multiple sclerosis.

PURPOSE

To translate and validate the modified fatigue impact scale into Arabic (MFIS-A) in patients with multiple sclerosis (MS).

METHODS

A total of 116 patients with relapsing remitting MS and 59 healthy participants were recruited. Fifty patients filled the MFIS-A twice with one week difference. Reliability was assessed by measuring Cronbach's and intraclass correlation coefficient (ICC). The MFIS-A was correlated with the fatigue severity scale (FSS), the vitality domain of the Short Form 36 (SF-36V), the fatigue visual analogue scale (VAS-F), and the Beck Depression Inventory II (BDI-II) to assess validity. Dimensionality of the MFIS-A was investigated. A receiver operating characteristic (ROC) curve analysis was done and specificity and sensitivity were calculated.

RESULTS

Factor analysis (based on 116 patients) revealed that the MFIS-A consists of two subscales: the physical/social and the cognitive subscales. The MFIS-A showed excellent test-retest reliability (ICC = 0.920) and internal consistency (Cronbach's  = 0.968). The minimal detectable change with 95% confidence interval was 14.68 (32.0%). The MFIS-A showed strong positive correlation with FSS and BDI-II, moderate positive correlation with VAS-F, negative moderate correlation with SF-36V, and weak correlation with EDSS. The MFIS-A differentiated healthy participants from patients with 79.3% sensitivity and 89.8% specificity.

CONCLUSIONS

The MFIS-A showed good validity and reliability indicating its usefulness as an assessment measure for patients with MS.IMPLICATIONS FOR REHABILITATIONMFIS-A is a valid and reliable tool for fatigue evaluation for patients with relapsing remitting MS.The optimal cutoff scores of the total MFIS-A, the physical/social, and cognitive subscales which indicate fatigue are 35.5, 18.5, and 15.5, respectively.Changes of 14.68 or more points may indicate a clinically important change (a true change) in fatigue in patients with MS.