Biomarkers of Alzheimer disease: current and future applications to diagnostic criteria.

PURPOSE OF REVIEW This article reviews recent advances in imaging and fluid biomarkers for Alzheimer disease (AD) and their application to newly proposed diagnostic criteria across the continuum of AD. RECENT FINDINGS There have been remarkable developments in neuroimaging markers for AD over the past decade, most notably the advent of positron emission tomography (PET) amyloid imaging using radiotracers that label fibrillar forms of amyloid-β (Aβ). Similarly, new research in CSF markers suggests CSF levels of Aβ1-42 and phosphorylated tau may be useful in the early diagnosis of AD and prediction of cognitive decline. The National Institute on Aging and the Alzheimer's Association recently convened three workgroups to develop joint recommendations for new diagnostic guidelines across the spectrum of AD. These recommendations incorporate biomarkers and propose updated criteria for the previously recognized stage of AD dementia, the evolving definition of mild cognitive impairment, and a newly proposed concept of stages of preclinical AD. SUMMARY Recent advances in AD biomarkers have increased the ability to detect evidence of early AD pathology in vivo. These biomarkers have been incorporated into new diagnostic recommendations, but a number of challenges remain for the biomarkers to become widely applied in clinical practice.