The diagnostic value of plasma Aβ42 and Aβ40 in Alzheimer's disease: current status, challenges, and impacting variables.

Alzheimer's disease (AD) is a group of central nervous system degenerative diseases that affect cognitive function. During the diagnosis of AD, the levels of amyloid-β 42 (Aβ42) and amyloid-β 40 (Aβ40) in plasma, as well as their ratio Aβ42/Aβ40, have recently been recommended by the International Association for the Study of Aging and Alzheimer's Disease as biomarkers to assist in clinical decision-making. However, an increasing amount of research data indicates that the effectiveness of these biomarkers is influenced by various factors. The levels of Aβ42 and Aβ40 are not only related to the physiological state of the human body, but also closely associated with the collection and preservation of plasma samples, pre-analytical processing, different detection methodologies, and even the result analysis process. Moreover, the functional status of metabolic organs in the human body, different comorbidities, bacterial or viral infections, and other factors can all affect the true levels of Aβ42 and Aβ40. Therefore, to clearly and comprehensively understand the advantages and limitations of plasma Aβ42 and Aβ40 as diagnostic biomarkers for AD, this article focuses on reviewing and discussing the influencing factors when plasma Aβ42 and Aβ40 are applied to the diagnosis of AD, aiming to help clinicians make better use of these indicators to optimize their diagnostic value.