A novel digital digit-symbol substitution test measures processing speed in adults at-risk for Alzheimer’s disease: A validation study (Preprint)

Abstract

Assessing cognitive constructs affected by Alzheimer’s disease, such as processing speed (PS), is important to screen for potential disease and allow early detection. Digital PS assessments have been developed to provide widespread, efficient cognitive testing, but all have been validated only based on the correlation between test scores. Best statistical practices dictate that concurrent validity should be assessed for agreement or equivalence, rather than utilizing correlation alone.

To assess the concurrent validity of a novel digital PS assessment against a gold-standard measure of PS.

Adults aged 45-75 years (n = 191) participated in this study. Participants completed the novel digital digit symbol substitution test (DDSST) and the Repeatable Battery for the Assessment of Neuropsychological Status coding test (RBANS-C). The correlation between test scores was determined using a Pearson’s product moment correlation and a difference in mean test scores between tests was checked for using a dependent samples t-test. Data were analyzed for agreement between the two tests using Bland-Altman limits of agreement and equivalency using a two one-sided tests approach.

A significant moderate, positive correlation was found between DDSST and RBANS-C scores (r = .577, p < .001), and no difference in mean scores was detected between tests (p = 0.93). Scores between tests were found to display adequate agreement and equivalence (p = .049).

Analyses indicate that the DDSST is a valid digital assessment of PS. The DDSST appears to be a suitable option for widespread, immediate, and efficient PS testing.

ClinicalTrials.gov Identifier: NCT04559789 https://clinicaltrials.gov/ct2/show/NCT04559789