Elecsys Total-Tau and Phospho-Tau (181P) CSF Assays: Analytical Performance of the Novel, Fully Automated Immunoassays for Quantification of Tau Proteins in Human Cerebrospinal Fluid

Background: Total tau (tTau) and phosphorylated 181P tau (pTau) are supportive diagnostic cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease. Manual CSF tau assays are limited by lot-to-lot and between-laboratory variability and long incubation/turnaround times. Elecsys Total-Tau CSF and Phospho-Tau (181P) CSF immunoassays were developed for fully automated cobas e analyzers, allowing broader access in clinical practice and trials.

Methods: Analytical performance, reproducibility, method comparisons with commercially available assays, and lot-to-lot and platform comparability (cobas e 601/411) of the Elecsys CSF assays were assessed. Tau distributions and concentration ranges were evaluated in CSF samples from two clinical cohorts.

Results: Both assays showed high sensitivity (limit of quantitation [LoQ]: 63 pg/mL [tTau]; 4 pg/mL [pTau]) and linearity over the measuring range (80-1300 pg/mL; 8-120 pg/mL), which covered the entire concentration range measured in clinical samples. Lot-to-lot and platform comparability demonstrated good consistency (Pearson's r: 0.998; 1.000). Multicenter evaluation coefficients of variation (CVs): repeatability, < 1.8%; intermediate precision, < 2.8%; between-laboratory variability, < 2.7% (both assays); and total reproducibility, < 6.7% (tTau) and < 4.7% (pTau). Elecsys CSF assays demonstrated good correlation with commercially available tau assays.

Conclusions: Elecsys Total-Tau CSF and Phospho-Tau (181P) CSF assays demonstrate good analytical performance with clinically relevant measuring ranges; data support their use in clinical trials and practice.