Advances in plasma biomarkers for the diagnosis of Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by memory impairment and deficits in other cognitive domains, ultimately leading to loss of independence in activities of daily living. As AD becomes an increasingly prevalent global health burden, the demand for early diagnosis of AD in clinical practice is growing. Due to factors such as accessibility, invasiveness, and testing costs, blood-based biomarkers (BBMs) are generally more favored by patients and more feasible compared to lumbar puncture or neuroimaging. Blood-based biomarkers may represent a breakthrough area for AD diagnosis. This review summarizes the AD biomarkers that have been widely studied to date, aiming to provide a comprehensive understanding of these markers to advance early diagnosis and offer valuable insights for clinical practice. First, we summarize the currently discovered biomarkers that can be used for AD diagnosis. It is noted that only a few highly promising biomarkers have been practically applied in the clinical auxiliary diagnosis of AD (including APOE genotyping for assessing genetic risk; Aβ42/Aβ40, P-tau181/Aβ42, and p-tau217 for differentiating AD; NfL for monitoring AD progression). It should be noted that current AD biomarkers are only applicable for clinical auxiliary diagnosis and cannot completely replace classic assessment scales for independent diagnosis. Additionally, we summarize the clinical advantages and potential challenges of these biomarkers, as well as the differences in their applicability to different populations. We emphasize that extensive clinical cohort studies are still needed in the future to further clarify the specificity of blood biomarkers and develop more suitable laboratory testing methods for clinical use to meet the clinical demand for high-sensitivity and high-specificity AD biomarker detection.