Diagnostic biomarkers of Alzheimer's disease: A state-of-the-art review

In 2018, there was a recent shift towards a biological definition of Alzheimer's disease (AD), based on biomarkers measured in vivo even before the onset of clinical dementia symptoms. No single biomarker can by itself accurately diagnose AD. A combination of biomarkers assessed through imaging and cerebrospinal fluid (CSF) yields better diagnostic accuracy. Although amyloid PET imaging and CSF levels of amyloid and tau deposits are increasingly used in AD clinical trials to increase diagnostic confidence in enrolled subjects, routine use of these biomarkers in clinical settings is still premature because of the risk of overdiagnosis, increased cost and/or invasiveness of the assessment method. Also, standardization of measures across studies is needed to assure biomarker regulatory approval. Exploring novel biomarkers beyond the amyloid and tau pathologies, and their longitudinal change across the AD continnum are important research avenues for the future.