Blood Testing May Be as Accurate as CSF Testing for Alzheimer Disease Biomarkers

Mass spectrometry-based blood testing assays for plasma phosphorylated tau at threonine 217 (p-tau217), a plasma biomarker for Alzheimer disease (AD), were as accurate as cerebrospinal fluid (CSF) tests in predicting cognitive impairment and dementia severity, according to research presented at the 2023 meeting of the Alzheimer’s Association International Conference (AAIC).

The study enrolled 337 patients with AD from the Knight Disease Research Center who previously received amyloid positron emission tomography (PET) testing to detect amyloid and CSF testing for AD biomarkers using the Lumipulse G1200 Automated Instrument Assay (Fujireibo US, Malvern, PA). An immunoprecipitation mass-spectrometry assay was conducted on plasma samples collected during the same session as CSF testing to measure plasma p-tau217 occupancy, calculated as the percent of phosphorylated to non-phosphorylated p-tau217. CSF and plasma p-tau217 assay results were compared to measures of dementia severity in participants as measured by Clinical Dementia Rating (CDR) and Clinical Dementia Rating Sum of Boxes (CDR-SB) scores.

Plasma p-tau217 occupancy testing was more accurate than CSF testing in correlation to both the measurement of cognitive impairment using CDR (AUC 0.876 and 0.814 respectively, P=.006) as well as measurement of dementia severity using CDR-SB (Spearman P=0.455 and -0.338 respectively, P=.02).

Accurate AD biomarker testing with easily administered assays, like the plasma p-tau217 assay, is of increasing importance in conjunction with the advancing development of disease-modifying therapies (DMTs) for AD. The authors of this study are affiliated with the Washington University in St. Louis School of Medicine, the Knight Alzheimer Disease Research Center, and the Tracy Family SILQ Center.