# Blood-based Biomarkers of Alzheimer’s Disease and Neurodegeneration in an Indigenous African Cohort using both SIMOA and NULISA Platforms

## TL;DR

This study explores blood-based Alzheimer's disease biomarkers in an African cohort using two advanced platforms, showing their potential for diagnosis and highlighting sex differences.

## Contribution

First application of SIMOA and NULISA platforms for AD biomarkers in an indigenous African cohort, revealing sex differences and platform concordance.

## Key findings

- Core AD biomarkers like p-tau 217, NfL, and GFAP increased with disease severity across diagnostic groups.
- Biomarker levels were consistently measured using both SIMOA and NULISA platforms.
- Male participants showed higher biomarker levels, and apoE E4 proteotype affected p-tau217 levels.

## Abstract

In low- and middle-income countries, Alzheimer’s disease and related dementias (ADRD) constitute a growing public health burden. Indeed, the lack of awareness and easy screening tools, such as blood-based biomarkers, leaves many patients undiagnosed. In this study, we explored the core biomarkers of AD in an indigenous African cohort (VALIANT) to assess their relevance and potential utility to aid clinical diagnosis.

Nigerian African older adults (n = 967; ≥50 years) participating in the VALIANT study completed a baseline cross-sectional evaluation with associated clinical diagnosis. We quantified phosphorylated tau (p-tau 217), glial fibrillary acidic protein (GFAP), neurofilament light (NfL), and amyloid beta (Aβ42 and Aβ40) levels in plasma with both the Single Molecule Assay (SIMOA, Quanterix) and Nucleic acid-Linked Immuno-Sandwich Assay (NULISA, Alamar) platforms.

In agreement with previous findings, core AD biomarkers were associated with disease severity both in clinical diagnostic and clinico-pathological groups, with stepwise increases of p-tau 217, NfL and GFAP from cognitively unimpaired (CU) to dementia (p < 0.05). These results were consistent across both SIMOA and NULISA platforms. Comparison between sexes showed higher levels of biomarkers in male participants across diagnostic groups. We identified a significant effect of apoE E4 proteotype on p-tau217 levels after adjusting for age and sex but no significant effect on the other AD biomarkers.

This first application of cutting-edge plasma AD biomarker immunoassay using two ultrasensitive platforms in an indigenous African cohort showed good concordance and underscores the relevance and utility of blood-based biomarkers of AD in diverse populations. Additionally, sex differences could unveil biological distinctions inherent in the African population.