A + T ± status across MCI and dementia due to AD: a clinic-based, retrospective study

Background: This study aimed at comparing, within the 2018 NIA-AA amyloidosis/tauopathy/neurodegeneration (ATN) framework, the distribution of T ± profiles across A + patients with MCI and dementia in a retrospective, single-center, clinic-based cohort. Methods: We retrospectively collected data on N = 168 A + patients with either MCI due to AD (N = 50) or probable AD dementia (ADD; N = 118). ATN status was assigned, according to the 2018 NIA-AA framework, based on cerebrospinal fluid (CSF) biomarker concentrations. A χ2-test for independent samples was run to compare the distribution of A + T + vs. A + T- profiles, regardless of N status, across MCI and dementia patients. Results: The most represented ATN profile in both groups was A + T + N + (MCI: 54%; dementia: 70.3%); 3.4% of dementia patients and none within the MCI cohort presented with an A + T-N + profile. When grouping ATN profiles solely based on A and T dimensions, the prevalence of A + T + was of 76.3% and 66% in dementia and MCI patients, respectively. No association between clinical diagnoses (i.e., MCI vs. dementia status) and AT profiles (i.e., A + T + vs. A + T-) was detected. Discussion: The distribution of A + T + vs. A + T- does not differ between MCI and ADD, with A + T + profiles being predominant in both clinical categories. This does not support the common notion of A + T- profiles being relatively more prevalent in MCI patients, as indexing an earlier and/or less severe disease. Hence, caution should be exerted in attributing a case of MCI to prodromal AD solely based on A-positivity in the presence of a T-negative profile.