Developing Topics

Background: There is increasing evidence that the pathogenesis of Alzheimer's disease (AD) involves various immunological responses. Indeed, astrocyte reactivity or astrocytosis is a pathological process that is commonly found surrounding amyloid-β plaques in the brains of AD patients. Although the exact role of astrocytosis is still unrevealed, monitoring astrocyte activity using biomarkers leads to a better understanding of the underlying mechanism of AD pathogenesis. Glial fibrillary acidic protein (GFAP) is commonly used as a reactive astrocyte biomarker following injury or stress in the central nervous system. Here, we developed an assay for plasma GFAP on the LUMIPULSE G platform, and evaluated the preliminary performance.

Method: The LUMIPULSE G System is a fully automated chemiluminescent enzyme immunoassay (CLEIA) platform that processes samples in ready-to-use immunoreaction cartridges within 30 minutes. The assay employs a pair of in-house developed monoclonal antibodies to detect GFAP. Analytical assay characteristics including sensitivity, precision and correlation between paired serum and plasma samples were assessed. The analytical studies comprised a series of buffer, EDTA plasma and serum samples, each tested in multiple replicates. Preliminary clinical performance was investigated using a small set of commercially- available samples.

Result: All tested analytical parameters met our acceptance criteria. Healthy control samples from a young age group exhibited results above the limit of quantification (LoQ). The LoQ was determined based on the assessment of low concentrated plasma GFAP samples. Imprecision was less than 10% CV for buffer-based as well as plasma samples. There was a statistically significant correlation between plasma and serum GFAP levels (r = 0.99, p <0.0001). ROC curve analysis showed the greatest AUC for plasma GFAP to distingish AD patients from healthy controls.

Conclusion: This preliminary evaluation of the Lumipulse G GFAP Plasma prototype assay showed promising results with regards to high sensitivity, low variability, and clinical utility. Further studies with well-characterised and diverse cohorts are needed to validate the assay's clinical performance.