Alzheimer’s disease (AD) is a neurodegenerative disorder hallmarked by extracellular amyloid-beta (AB) plaques and intracellular neurofibrillary tangles of hyperphosphorylated tau (p-tau), which lead to progressive loss of neuronal function and cell death (1). These pathologies can be present and developing in the brain for years before any symptoms become apparent (2). During this buildup there are several specific proteins that are released into the cerebrospinal fluid (CSF) that have been identified as reliable biomarkers for the diagnosis of AD.
Tau protein normally acts to stabilize the axons of neurons, but when it is hyperphosphorylated (p-tau) it becomes prone to aggregating into neurofibrillary tangles, leading to neuronal dysfunction and death (3), There are several variants of p-tau that have been identified as significant in AD, differentiated by the location of the phosphorylation site.
The two most notable isoforms are p-tau 181 and p-tau 217. Levels of p-tau 181 and 217 in both CSF and blood have been shown to be elevated in AD and increase over the course of the disease, indicating they could be a valuable tool for diagnosis (4,5), but the relative performance of the two has been an area of intense interest.
Studies have consistently found that p-tau 217 levels are more sensitive and specific than p-tau 181 levels in distinguishing between AD and other neurodegenerative disorders (5-7). p-tau-217 also shows greater correlation with tau- and amyloid-positron emission tomography (PET) imaging, gold standards for detecting AD pathology in the brain (6,7).
Our assay is a single analyte, ultra-sensitive Simoa immunoassay for the accurate quantification of p-tau 217 levels in blood. This cutting-edge technique analyzes plasma samples with an automated system of sample preparation, data collection, and analysis. Results are reported in pg/mL and include an interpretation based on normal p-tau 217 concentration ranges.