Associations of Antemortem Cerebrospinal Fluid Biomarkers with Alzheimer’s Disease Neuropathologic changes at Autopsy

Abstract

AbstractBackgroundCerebrospinal fluid (CSF) amyloid‐beta 42 (Aβ42) and tau phosphorylated at threonine 181 (p‐tau181) have been widely used as biomarkers for Alzheimer’s disease (AD). AT(N) classification even proposes each substance as a direct biomarker of amyloid (A) and tau (T) pathologies, respectively. However, recent studies suggest that increased CSF p‐tau181 may rather be associated with amyloid pathology. Although neuropathological evaluation at autopsy is the gold standard for assessing these changes, studies evaluating the association between CSF biomarkers and AD neuropathologic changes are limited.MethodWe retrospectively studied patients who underwent antemortem CSF AD biomarker measurement and neuropathological evaluation at autopsy at our institution from 1995 to 2021. CSF biomarkers were measured by ELISA (Fujirebio, Belgium). Neuropathological evaluation of AD was performed routinely regardless of diagnosis and Thal phase, Braak neurofibrillary tangle (NFT) stage, and CERAD score were assessed according to current guidelines.ResultThe mean age of the 119 patients was 76.2 ± 8.9 years; 49 were women. The duration from lumbar puncture to autopsy was median 2 years (0‐13 years). AD pathology was observed in 29 patients (24%). Other common pathologies were Lewy body disease and frontotemporal lobar degeneration. Antemortem CSF Aβ42 and p‐tau181 results were obtained in 119 and 68 patients, respectively. As expected, CSF Aβ42 decreased with increasing Thal phase and CERAD score. CSF p‐tau181 increased with increasing Thal phase, Braak NFT stage, and CERAD score. Even when the analysis was restricted to patients with Braak NFT stage 3 or less (n = 48), CSF p‐tau181 increased mildly with increasing Thal phase and CERAD score. In patients with moderate or severe amyloid pathology by Thal phase or CERAD score (n = 34), CSF p‐tau181 increased more highly at Braak NFT stage 5 or more.ConclusionThe results of this study, which directly compared antemortem CSF biomarkers with AD neuropathologic changes at autopsy, support the current theories that increased CSF p‐tau181 is caused by both amyloid and tau pathology related to AD while decreased CSF Aβ42 is associated with amyloid pathology.