Box 4 | Expert opinion on blood-based biomarkers

• While blood-based biomarkers are currently limited to the research setting, in general, they are useful for screening and stratifying AD, monitoring disease progression, and predicting therapeutic response to      DMT. They are more easily assessable than CSF biomarkers, especially for repeated assessments

• The plasma Aβ42/Aβ40 ratio, P-tau181, and P-tau217 have the potential for triaging patients in the primary care setting for further testing using PET imaging or CSF biomarkers

• Plasma P-tau181 and P-tau217 have a potential role in stratifying risk of progression from prodromal dementia to AD dementia

• Plasma NfL is a biomarker for neurodegeneration in several cognitive disorders and may be a feasible screening test and tool to monitor disease progression

• The expert group highlights the need for fluid biomarkers to undergo a phase of standardization to harmonize assay platforms and define Asian reference and cut-off values

• A panel of fluid biomarkers reflecting amyloid and tau pathology, as well as neurodegeneration, would be imperative for the application of these blood tests in research and clinical practice

• If accurate blood-based biomarkers are made available at a reasonable cost to patients, they may become a standard part of the dementia workup to predict risk and screen for AD

• Blood-based biomarkers may offer an opportunity for greater health equity, facilitating research into AD progression across larger and more representative populations

AD, Alzheimer’s disease; CSF, cerebrospinal fluid; DMT, disease-modifying therapy; NfL, neurofilament light protein; PET, positron emission tomography; P-tau181, threonine-181-phosphorylated tau; P-tau217, tau phosphorylated at threonine 217