Fluid biomarkers in the evolving care landscape of Alzheimer's disease and related disorders.

Fluid biomarkers for Alzheimer's disease have advanced rapidly during the past several years driven by breakthroughs including development of ultrasensitive and multiplexing technologies and high specificity antibodies. Blood-based biomarkers, such as neurofilament light for frontotemporal dementia and amyotrophic lateral sclerosis, and phosphorylated tau 217 for the diagnosis of Alzheimer's disease, are now being implemented in clinical practice, which is particularly timely because of the increasing clinical availability of amyloid-targeting treatments in Alzheimer's disease. Multiple fluid biomarkers are needed to capture the complexity of disease mechanisms for precise diagnosis and to measure the diverse pathologies that lead to dementia, such as vascular, α-synuclein, and TDP-43 pathologies. Moreover, fluid biomarkers can aid in capturing heterogeneity in treatment course between patients, probably due to copathologies or key intermediates, including microglia and astrocyte dysregulation. Increased focus on biomarker-pathology relationships in experimental models will likely accelerate biomarker development and further the understanding of their precise substrates. Future clinical implementation of biomarkers to capture the full complexity of pathologies will likely be facilitated by the expansion of diagnostic methods, development of point of care technologies, and remote sampling approaches.