Smartphone-based symbol-digit modalities test reliably captures brain damage in multiple sclerosis.

Area of Science:

• Neuroscience
• Digital Health
• Biomarker Development

Background:

• Increasing burden of neurodegenerative diseases necessitates improved methods for assessing complex neurological functions beyond limited clinic visits.
• Patient-collected digital biomarkers hold promise for continuous monitoring, but their psychometric properties require thorough evaluation.
• Existing cognitive tests often lack the granularity needed for frequent, remote assessment.

Purpose of the Study:

• To develop and validate a smartphone-based adaptation of the Symbol-Digit Modalities Test (SDMT) for assessing cognitive function.
• To evaluate the psychometric properties of the smartphone SDMT in individuals with multiple sclerosis (MS) and healthy volunteers (HV).
• To compare the performance of the smartphone SDMT against traditional SDMT and neurological/radiological measures.

Main Methods:

• Developed a smartphone version of the SDMT with randomized symbol-number codes and testing sequences.
• Recruited 154 MS patients and 39 HV to undergo both smartphone and traditional SDMT.
• Correlated SDMT performance with cognitive subscores from neurological exams and MRI-measured brain injury.
• Utilized a separate smartphone test to measure motoric hand disability for mathematical adjustment.

Main Results:

• The smartphone SDMT demonstrated comparable psychometric properties to the traditional SDMT in both MS patients and HV.
• Smartphone SDMT showed slightly higher correlations with cognitive function scores (R²=0.75) and MRI-assessed brain injury (Rho=0.83) than the traditional version.
• Mathematical adjustment for motoric hand disability improved the accuracy of the touch-based smartphone test.
• Averaging granular home measurements enhanced the accuracy of detecting neurological decline.

Conclusions:

• The smartphone SDMT is a psychometrically sound digital biomarker for assessing cognitive function in neurodegenerative diseases.
• This digital tool can provide reliable, granular data for monitoring neurological decline, complementing traditional clinical assessments.
• Smartphone-based cognitive testing offers a scalable and accessible approach to managing the growing burden of neurological disorders.