Preclinical detection of Alzheimer's disease pathology using conceptual discrimination abilities.

Background: Performance on the Conceptual Matching Task (CMT), a measure of discrimination between conceptually confusable items, has been suggested as a cognitive marker of rhinal cortex atrophy, one of the first brain regions affected by Alzheimer's disease (AD) pathology.

Objectives: We aimed to determine whether CMT can detect preclinical AD, and whether CMT performance is related to regional deposition of tau protein or other AD-associated lesions including amyloid (Aβ) accumulation and white matter hyperintensities (WMH).

Design, setting and participants: This cross-sectional study include 101 participants from the UCL2016-121 cohorts in Brussels, Belgium, classified as 56 Aβ-negative cognitively unimpaired (Aβ-CU), 25 Aβ-positive CU (Aβ+CU, preclinical AD), and 20 Aβ-positive mildly cognitively impaired (Aβ+MCI, prodromal AD) individuals.

Measurements: Participants underwent CMT and a standard neuropsychological assessment that included the Preclinical Alzheimer Cognitive Composite (PACC5), an Aβ status examination, a 3D-T1 MRI and a [¹⁸F]MK-6240 tau-PET scan.

Results: CMT performance was lower among Aβ+MCI and Aβ+CU than Aβ-CU individuals. The effect of Aβ on CMT performance was stronger in the presence of WMH, but rhinal tau burden did not explain CMT performance beyond the effects of Aβ and WMH. CMT performance correlated with executive, memory, and language performance. Finally, CMT was more sensitive than PACC5 to detect CU individuals with Aβ or tau pathology.

Conclusion: Given that impaired performance is observed earlier in the CMT than in standard neuropsychological tests, this test shows promise as an early diagnostic tool for AD and may offer significant utility in the context of clinical trials.