Psychometric evaluation of the ReacStick: A feasible and valid tool for assessing processing speed and executive function in multiple sclerosis.

BACKGROUND: Processing speed and executive functions are commonly impaired in people with multiple sclerosis (PwMS). ReacStick is a novel, portable device designed to assess these domains. Although validated in other clinical populations, its utility has not been evaluated in PwMS. This study aimed to evaluate the feasibility, validity, and reliability of ReacStick in PwMS. METHODS: ReacStick uses a "ruler drop" paradigm to determine simple reaction time (SRT) and short latency (390-millisecond) decision-making based on ability to catch, or withhold catching, the device based on a light cue (reaction accuracy). Completion rates determined feasibility. Correlations with standard cognitive measures and comparisons across MS subgroups evaluated construct validity. Relative and absolute indices determined reliability. RESULTS: 99.6% of participants completed the protocol, indicating high feasibility; the only incomplete session resulted from device malfunction. ReacStick metrics moderately correlated with processing speed and executive function measures (r = -0.37 to 0.51) and weakly with language tests (r ≤ 0.13). Scores differed by disability and MS subgroup. SRT showed excellent reliability (ICC = 0.92); reaction accuracy showed moderate-to-good reliability (Spearman-Brown = 0.51-0.76). CONCLUSIONS: ReacStick is a feasible, valid, and reliable tool for cognitive assessment in MS. Its brief and portable format supports its use in both clinical and research settings.