Validity of the Symbol Digit Modalities Test as a cognition performance outcome measure for multiple sclerosis

Abstract

Cognitive and motor performance measures are commonly employed in multiple sclerosis (MS) research, particularly when the purpose is to determine the efficacy of treatment. The increasing focus of new therapies on slowing progression or reversing neurological disability makes the utilization of sensitive, reproducible, and valid measures essential. Processing speed is a basic elemental cognitive function that likely influences downstream processes such as memory. The Multiple Sclerosis Outcome Assessments Consortium (MSOAC) includes representatives from advocacy organizations, Food and Drug Administration (FDA), European Medicines Agency (EMA), National Institute of Neurological Disorders and Stroke (NINDS), academic institutions, and industry partners along with persons living with MS. Among the MSOAC goals is acceptance and qualification by regulators of performance outcomes that are highly reliable and valid, practical, cost-effective, and meaningful to persons with MS. A critical step for these neuroperformance metrics is elucidation of clinically relevant benchmarks, well-defined degrees of disability, and gradients of change that are deemed clinically meaningful. This topical review provides an overview of research on one particular cognitive measure, the Symbol Digit Modalities Test (SDMT), recognized as being particularly sensitive to slowed processing of information that is commonly seen in MS. The research in MS clearly supports the reliability and validity of this test and recently has supported a responder definition of SDMT change approximating 4 points or 10% in magnitude.

Preserved network functional connectivity underlies cognitive reserve in multiple sclerosis

“…The networks of GM regions whose WM tract disruption was significantly associated with each cognitive domain are consistent with expectations. Impairment of cognitive processing speed as measured by SDMT was significantly related to a much more diffuse network of structurally disrupted pairs of GM regions (Figure 4), which is consistent with our understanding of SDMT as a cognitive assessment that is highly sensitive to structural damage in PwMS (Benedict et al, 2017 (Birn et al, 2013), future work should consider longer acquisition times. These results confirm the role of right hemispheric ventral visual pathways and hippocampal networks in visual/spatial processing and memory (De Schotten et al, 2011;Kravitz, Saleem, Baker, Ungerleider, & Mishkin, 2013;Squire, Kosslyn, Zola-Morgan, Haist, & Musen, 1992).…”

Neurofilament light chain serum levels correlate with 10‐year MRI outcomes in multiple sclerosis

“…EDSS and T2FW are collected in all CLIMB subjects annually. Subjects in the QOL subgroup of CLIMB annually completed several patient reported outcomes (PROs) and this analysis included a fatigue measurement (modified fatigue impact scale, MFIS)21 and cognition (symbol digit modalities test, SDMT) 22…”

Cognitive impairment as one of the important non‐motor symptoms in multiple sclerosis and neuromyelitis optica spectrum disorders

“…47 For the CVLT2, words were culturally adapted for the Japanese population, and the Japanese version of the CVLT2 has been recently validated in the literature. 59 The SDMT, which is one of the tests included in the MACFIMS, BRB-N and BICAMS, is among the best psychometric tools for assessing cognitive processing speed, which seems to be more frequently impaired in patients with MS. 10,46,57,60 The SDMT is a good test to predict cognitive impairment in patients with MS, even patients who are in the early stages of the disease. 56 The MACFIMS and the BRB-N are optimal for a more comprehensive investigation of the cognitive profile than the BICAMS, and might be more suitable to identify changes in cognition over time than the BICAMS.…”