Comparative analysis of Elecsys and ELISA for differentiating amyloid-PET status in a Korean memory clinic based on cerebrospinal fluid biomarkers.

Abstract

Background: The adoption of Alzheimer's disease (AD) biomarkers in clinical practice is expected to increase following recent approval of disease-modifying therapies. Fully automated immunoassays, Elecsys platform, offer convenience and enhanced reliability.

Objective: This study was performed to evaluate the performance of the Elecsys assay in a Korean clinical setting, comparing its effectiveness to ELISA for detecting amyloid-PET positivity.

Methods: Cerebrospinal fluid (CSF) Aβ₄₂, pTau₁₈₁, tTau, pTau₁₈₁/Aβ₄₂, and tTau/Aβ₄₂ were evaluated using Elecsys kits on a Cobas e 411 analyzer and manual Innotest ELISA with paired frozen samples (n = 118) from subjects with cognitive status ranging from unimpaired to mild cognitive impairment and dementia.

Results: Strong linear correlations were observed between Elecsys- and ELISA-measured Aβ₄₂, pTau₁₈₁, and tTau levels. Receiver operating characteristic-based cutoff points for pTau₁₈₁/Aβ₄₂ (0.0252) and tTau/Aβ₄₂ (0.258) in Elecsys demonstrated the highest areas under the curve (0.97 and 0.96) and predictive values (96.6% for both) for detecting amyloid-PET abnormalities. No cases of abnormal amyloid PET status were found without concurrent abnormal CSF biomarkers when considering Elecsys Aβ₄₂ and the pTau₁₈₁/Aβ₄₂ ratio simultaneously. In addition, previously established cutoffs for combined ratios effectively differentiated amyloid PET status in our samples.

Conclusions: This study demonstrated the utility of Elecsys-measured CSF AD biomarkers in agreement with amyloid-PET classification in the Korean population. The pTau₁₈₁/Aβ₄₂ and tTau/Aβ₄₂ ratios were the most accurate in detecting amyloid-PET (+), with Elecsys showing higher accuracy than ELISA. The study also supported the applicability of common cutoffs from Western countries for these biomarkers in our samples.