Search

Background: Recently developed blood markers for Alzheimer's disease (AD) detection have high accuracy but usually require ultra-sensitive analytic tools not commonly available in clinical laboratories, and their performance in clinical practice is unknown., Methods: We analyzed plasma samples from 290 consecutive participants that underwent lumbar puncture in routine clinical practice in a specialized memory clinic (66 cognitively unimpaired, 130 participants with mild cognitive impairment, and 94 with dementia). Participants were classified as amyloid positive (A +) or negative (A-) according to CSF Aβ 1-42 /Aβ 1-40 ratio. Plasma pTau 217 , pTau 181 , Aβ 1-42 and Aβ 1-40 were measured in the fully-automated LUMIPULSE platform. We used linear regression to compare plasma biomarkers concentrations between A + and A- groups, evaluated Spearman's correlation between plasma and CSF and performed ROC analyses to assess their diagnostic accuracy to detect brain amyloidosis as determined by CSF Aβ 1-42 /Aβ 1-40 ratio. We analyzed the concordance of pTau 217 with CSF amyloidosis., Results: Plasma pTau 217 and pTau 181 concentration were higher in A + than A- while the plasma Aβ 1-42 /Aβ 1-40 ratio was lower in A + compared to A-. pTau 181 and the Aβ 1-42 /Aβ 1-40 ratio showed moderate correlation between plasma and CSF (Rho = 0.66 and 0.69, respectively). The areas under the ROC curve to discriminate A + from A- participants were 0.94 (95% CI 0.92-0.97) for pTau 217 , and 0.88 (95% CI 0.84-0.92) for both pTau 181 and Aβ 1-42 /Aβ 1-40 . Chronic kidney disease (CKD) was related to increased plasma biomarker concentrations, but ratios were less affected. Plasma pTau 217 had the highest fold change (× 3.2) and showed high predictive capability in discriminating A + from A-, having 4-7% misclassification rate. The global accuracy of plasma pTau 217 using a two-threshold approach was robust in symptomatic groups, exceeding 90%., Conclusion: The evaluation of blood biomarkers on an automated platform exhibited high diagnostic accuracy for AD pathophysiology, and pTau 217 showed excellent diagnostic accuracy to identify participants with AD in a consecutive sample representing the routine clinical practice in a specialized memory unit., (© 2024. The Author(s).)