Processing speed test as an alternative to the symbol digit modalities test for cognitive screening in multiple sclerosis

To replicate previous findings on the validity of the Processing Speed Test (PST) as a potential alternative to the Symbol Digit Modalities Test (SDMT) for assessing neurocognitive function in patients with multiple sclerosis (MS), and to further confirm its associations with demographic, clinical, neuropsychological, radiological, and sociodemographic factors.

A cross-sectional study was conducted with 219 adults diagnosed with relapsing remitting MS. Cognitive assessment included the Brief International Cognitive Assessment for MS (BICAMS) battery-comprising SDMT, California Verbal Learning Test, and Brief Visuospatial Memory Test-Revised-alongside the PST, which is self-administered on a digital device. Fatigue and mood were measured using the Modified Fatigue Impact Scale and Beck Depression Inventory-Second Edition (BDI-II), respectively. Also clinical, demographic, and magnetic resonance image variables were collected. Correlations between PST, SDMT, and other cognitive, demographic, clinical and radiological measures were calculated.

PST exhibited a strong positive correlation with SDMT (rho=0.814, p < 0.001) and similar associations with other BICAMS subtests. Lower PST scores were associated with older age higher fatigue, depression, disability, and lesion burden; while higher educational level was linked to better performance.

These findings replicate and strengthen prior evidence supporting the PST as a valid cognitive screening tool in MS. Its self-administered and automated scoring supports its use as a practical alternative to SDMT for routine clinical screening. Further longitudinal studies are needed to confirm its utility for monitoring cognitive changes over time.