Abstract
Alzheimer's disease (AD) is a growing health crisis around the world. Although significant progress has been made in our understanding of AD pathogenesis, there is currently no effective treatment to delay onset or prevent the disease. The focus has now shifted to the identification and treatment of AD in the early clinical stages as well as before cognitive symptoms emerge-during the long preclinical stage. It is possible that diagnosis of individuals with AD will be more accurate when clinical symptoms and signs are combined with biomarkers, which can improve both the diagnostic and prognostic accuracy of AD and its differentiation from the other neurodegenerative diseases. This review discusses fluid and imaging biomarkers that have shown promise in such areas, as well as some of the current challenges that face the field.