Test-retest reliability of cognitive fatigability measures during the SDMT and PASAT in people with multiple sclerosis

Objective: Cognitive capacity tests can measure cognitive fatigability (CF) in persons with multiple sclerosis (pwMS). This study investigated test–retest reliability of CF measures using Paced Auditory Serial Addition Test (PASAT) and Symbol Digit Modalities Test (SDMT). Methods: CF index (CFI%) comparing the last and first thirds and delta scores of SDMT and PASAT were assessed in 49 pwMS (EDSS:3–6.5) and 23 healthy controls. Tests were performed twice 5–7 days apart. Results: Both groups showed a performance decline (−2 to −21%). CFI and delta showed poor reliability in both groups (ICC range = 0.04–0.36). Conclusions: CF measures exhibited low reliability in pwMS.