Reliability and validity of the Persian version of the Fatigue Scale for Motor and Cognitive Functions (P-FSMC) in Iranian people with multiple sclerosis.

Purpose This study evaluated the psychometric feature of the Persian version of the Fatigue Scale for Motor and Cognitive Functions (P-FSMC) in Iranian People with Multiple Sclerosis (PwMS). Materials And Methods In this cross-sectional study, 303 PwMS and 102 healthy controls participated. Structural validity was explored using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Construct validity was determined through correlations of P-FSMC with the Fatigue Severity Scale (FSS) and the Fatigue Impact Scale (FIS), besides expected differences in P-FSMC scores and by examining score variations based on disability and depression levels. Fatigue discrimination and diagnostic accuracy between PwMS and healthy controls were evaluated. Results The P-FSMC demonstrated excellent test-retest reliability and high internal consistency. EFA revealed two factors explaining 70.08% of the variance, with good fit model. The P-FSMC showed moderate to high correlations with FSS and FIS and distinguished different levels of disability and depression. The total score discriminated fatigue with 86.7% accuracy, 84.5% sensitivity, and 93.1% specificity. Cut-off scores for mild, moderate, and severe fatigue severity were ≥46, ≥56, and ≥66, respectively, with high sensitivity (81.52-91.42%) and specificity (80.02-99.01%). Conclusions The P-FSMC is a reliable and valid questionnaire for assessing fatigue in Iranian PwMS.The Fatigue Scale for Motor and Cognitive Functions, as a two-dimensional instrument, uniquely assesses fatigue severity across cognitive and motor dimensions, setting it apart from other tools.The separation of domains helps to understand the impact of potentially confounding variables and elucidate the mechanisms that lead to fatigue.The Persian version of the Fatigue Scale for Motor and Cognitive Functions appears to be valid and reliable for individuals with multiple sclerosis, indicating its potential use in clinical setting and research.