Differential Validity in the Written, Oral, and Electronic SDMT in Multiple Sclerosis

Area of Science:

• Neuroscience
• Psychometrics
• Clinical Neurology

Background:

• Cognitive decline in multiple sclerosis (MS) is often evaluated using the Symbol Digit Modalities Test (SDMT).
• Written (wSDMT), oral (oSDMT), and electronic (eSDMT) SDMT versions are used interchangeably, but may have different psychometric properties.

Purpose of the Study:

• To compare the psychometric properties of wSDMT, oSDMT, and eSDMT in individuals with MS.
• To assess inter-test reliability and the influence of demographic factors and motor disability on performance across SDMT versions.

Main Methods:

• A within-subjects design was employed with 85 MS participants completing all three SDMT versions.
• Intraclass correlation coefficients (ICCs) and sequential multiple regression were used for statistical analysis.

Main Results:

• All three SDMT versions showed good inter-test reliability (ICC = 0.77) and comparable mean scores.
• Scores on all versions declined with age, with a steeper decline observed in the eSDMT.
• Motor disability influenced wSDMT and eSDMT scores, while age and education most significantly impacted eSDMT performance.

Conclusions:

• The eSDMT demonstrates greater sensitivity to age and education compared to wSDMT and oSDMT.
• Motor disability affects wSDMT and eSDMT performance.
• Differential construct validity highlights the need for version-specific normative data and motor adjustments in MS cognitive assessments.