Characterization of AD pathology based on plasma biomarkers measured by a fully automated immunoassay system (HISCL^TM series)

Abstract

Background There have been a lot of studies on classification of Alzheimer’s disease (AD) based on its pathological process. These pathological changes have been defined by the ATN classification system (A : amyloid β (Aβ) deposition, T : pathogenic tau, N : neurodegeneration) based on cerebrospinal fluid (CSF) biomarker levels or neuroimaging. In order to promote research and practical application, it is necessary to develop a cost effective and minimally invasive technology. Therefore, we have developed plasma Aβ1‐40, Aβ1‐42, threonine‐181 phosphorylated tau (p‐tau181) and total‐tau immunoassay systems and reported that these plasma biomarkers levels were significantly different between AD and cognitively normal (CN). In this study we have measured biomarkers in other sample sets including mild cognitive impairment (MCI), and evaluated the performance in characterizing AD pathology, in the context of the ATN classification system. Method We measured commercially available plasma and CSF samples on the HISCLTM series, which can achieve high degrees of sensitivity and fast measurement times of 17 minutes, requiring only 10 to 30 µl of samples. The concentration of plasma and CSF biomarkers levels (Aβ1‐40, Aβ1‐42, p‐tau181, total‐tau) were measured and the significance of the difference between AD, MCI and CN groups was assessed. Result The AD group had lower Aβ1‐42/Aβ1‐40 ratio and higher levels of p‐tau181 and t‐tau compared to MCI or CN groups. The levels of plasma biomarkers in MCI group showed wide distribution compared to AD or CN group, suggesting these plasma biomarkers reflect the various pathological states of dementia in MCI patients. This might indicate that our plasma biomarker measurement systems represent characterization of AD pathological processes. Conclusion Our assay system revealed that the distribution of plasma biomarkers showed characteristic distribution in AD, MCI and CN groups, respectively. This result may indicate the possibility of practical diagnosis of AD pathology based on plasma biomarker ATN classification system. We aim to continue to measure other clinical sample sets for evaluation of the usefulness and universality of plasma biomarkers.