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

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) Aβ 42 , pTau 181 , tTau, pTau 181 /Aβ 42 , and tTau/Aβ 42 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 Aβ 42 , pTau 181 , and tTau levels. Receiver operating characteristic-based cutoff points for pTau 181 /Aβ 42 (0.0252) and tTau/Aβ 42 (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 Aβ 42 and the pTau 181 /Aβ 42 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 pTau 181 /Aβ 42 and tTau/Aβ 42 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.