# Head-to-head comparison of plasma p-tau217 immunoassays for incipient Alzheimer’s disease in community cohorts

## TL;DR

This study compares four plasma p-tau217 assays for detecting early Alzheimer’s disease in diverse community-based groups.

## Contribution

The study provides a direct comparison of p-tau217 assays in diverse community cohorts, revealing their equivalent performance in detecting amyloid positivity.

## Key findings

- All four p-tau217 assays showed moderate to strong cross-platform correlations (Spearman correlations of 0.40–0.86).
- The assays had statistically equivalent AUCs (0.84–0.90) for determining Aβ positivity in diverse older adult populations.

## Abstract

Plasma p-tau217 is a promising biomarker for detecting incipient AD pathology, but direct comparison of different p-tau217 assays in community-based cohorts are limited.

We evaluated two cohorts from southwestern Pennsylvania, USA; the MYHAT-NI sub-study, which included two-year longitudinal follow-up neuroimaging assessments of Aβ, tau, and cortical thickness; and the Human Connectome Project/CoBRA, targeting a 50:50 split of self-identified Black and non-Hispanic White individuals. Plasma p-tau217 was measured using four different assays: Lumipulse, Johnson&Johnson, ALZpath, and NULISA. Aβ and tau pathologies were assessed with [11C]PiB PET and [18F]Flortaucipir PET, respectively. Clinical Dementia Rating (CDR) and Montreal Cognitive Assessment were used to assess cognitive performance.

We included 344 participants (MYHAT-NI: n=111, median age 76 [IQR: 72–80], 54% female; HCP/CoBRA: n=234, median age 62 [IQR: 52–70], 65% female). All four p-tau217 assays exhibited moderate to strong cross-platform correlations (Spearman correlations of 0.40 – 0.86), and statistically equivalent AUCs (of 0.84–0.90) for determining Aβ positivity.

Our findings showed strong equivalent performances of plasma p-tau217 assays to identify amyloid positivity across two highly diverse cohorts of community-dwelling older adults.