Development of a light-initiated chemiluminescence system for the detection of human plasma p-tau181.

Phosphorylated tau 181 (p-tau181) is a promising biomarker for predicting and monitoring Alzheimer's disease (AD) neuropathology. However, existing commercial assays suffer from disadvantages such as high cost and insufficient detection sensitivity, limiting their clinical applications and suitability for routine laboratory use. In this study, we developed a novel light-initiated chemiluminescence assay (LiCA®) and evaluated its performance for quantifying plasma p-tau181 levels. A compact, fully automated LiCA® analyzer was developed for decentralized and point-of-care testing environments. Analytical performance of the p-tau181 assay on the analyzer was validated according to Clinical and Laboratory Standards Institute (CLSI) guidelines, with evaluation of precision, accuracy, linearity, detection capability, and interference. Reference intervals were established per EP28-A3c. Method comparison was conducted using Spearman's correlation with the Simoa® pTau-181 Advantage V2.1 kit. The assay demonstrated excellent precision (coefficient of variation: 2.72-5.11%), high recovery accuracy (93.29-107.56%), and strong linearity (R = 0.9986) across a range of 0-200 pg mL-1. Sensitivity parameters included limit of blank (LoB) = 0.10 pg mL-1, limit of detection (LoD) = 0.19 pg mL-1, limit of quantitation (LoQ) = 0.30 pg mL-1 (20% CV) and LoQ = 0.57 pg mL-1 (10% CV). Plasma p-tau181 was detectable in 100% of healthy individuals (n = 400), confirming the assay's capability for baseline differentiation. Strong correlation with the Simoa® platform (ρ = 0.868) further validated clinical concordance. LiCA® offers a fully automated, random-access platform for highly sensitive and accurate measurement of p-tau181. It could be a viable tool for early screening and differential diagnosis of neurodegenerative diseases in both clinical trial settings and routine clinical practice.