image: Overview of the CLEAR-AD study evaluating the diagnostic accuracy of nine commercial plasma p-tau217 assays against amyloid PET imaging in a multicenter memory clinic cohort.
Credit: ©Science Bulletin
With the arrival of disease-modifying therapies for Alzheimer's disease, accessible and accurate diagnostic tools have become essential. Blood-based biomarkers, particularly phosphorylated tau at threonine 217 (p-tau217), offer a promising, non-invasive alternative to spinal taps and costly PET imaging scans. However, the rapid emergence of commercial p-tau217 tests has created clinical uncertainty, as their diagnostic accuracy has rarely been directly compared within the same patient cohort.
To address this gap, researchers conducted the Clinical Evaluation of Blood-Based Tests for the Rapid Identification of Amyloid Pathology in AD (CLEAR-AD) study. This multicenter diagnostic accuracy study included 431 participants from ten memory clinics across China, spanning cognitively unimpaired individuals, patients with mild cognitive impairment, and patients with dementia. Blood samples were evaluated in a central laboratory using nine commercially available p-tau217 assays across three distinct analytical platforms, with diagnostic performance benchmarked against brain amyloid PET scans.
The results revealed noticeable performance variations among the tests. Seven of the nine assays demonstrated strong accuracy in detecting amyloid PET positivity. However, two assays exhibited substantially lower diagnostic discrimination. These findings indicate that plasma p-tau217 tests should not be treated as a uniform, interchangeable diagnostic category, as clinical utility depends heavily on the specific analytical platform used.
The research team also evaluated a two-cutoff interpretation strategy designed to rule in or rule out amyloid pathology. For the top-performing assays, this approach maintained a high level of diagnostic certainty while keeping intermediate, inconclusive results within a small, clinically manageable range. Additionally, adding plasma amyloid-beta measurements to derive a biomarker ratio provided diagnostic benefits only in specific patient subgroups, such as those with mild cognitive impairment.
External cutoffs recommended by manufacturers or prior studies also showed variable performance in this independent cohort, reinforcing the necessity of calibrating threshold values prior to real-world clinical implementation. Overall, the CLEAR-AD study supports the clinical translation of high-performing plasma p-tau217 assays to streamline diagnostic workflows, provided that platform-specific calibration and standardized protocols are established.
About the University of Science and Technology of China
The University of Science and Technology of China (USTC) is a premier national research university under the Chinese Academy of Sciences, renowned for its cutting-edge advancements in science, technology, and biomedical research.