Association of the Processing Speed Test with depression and brain magnetic resonance imaging metrics in Japanese patients with multiple sclerosis

Objectives Cognitive dysfunction occurs in a substantial proportion of patients with multiple sclerosis (MS). The Processing Speed Test (PST) is a self‐administered, tablet‐based cognitive screening tool that closely resembles the Symbol Digit Modalities Test and can be quickly administered. In this study we assessed the performance of the PST and its correlation with the clinical and radiological aspects of MS in Japanese patients. Methods PST was administered to 52 Japanese patients with MS. The Beck Depression Inventory Second Edition (BDI‐II), Fatigue Severity Scale (FSS), and Functional Assessment of MS (FAMS) were used to evaluate depression, fatigue, and health‐related quality of life, respectively. Global and regional brain volumes and cortical thickness were analyzed based on 3D T1‐weighted magnetic resonance images. Results The mean ± standard deviation of the PST score was 52.5 ± 16.5. Negative correlations were observed between PST score and age, disease duration, and the Expanded Disability Status Scale (EDSS). The PST score showed significant correlation with BDI‐II after adjusting for disease duration and EDSS. In contrast, no significant association was observed between PST score and FSS, FAMS total score, and employment status after adjusting for disease duration, EDSS, and BDI‐II. The PST score showed significant correlation with global and regional brain volumes, and the thickness of bilateral temporal cortexes. Conclusion The PST score was associated with the severity of depression and both global and regional brain volume in Japanese patients with MS. Our findings support the validity of the PST as a useful tool for assessing the cognitive function of MS patients in clinical practice.