Biomarkers for Alzheimer's disease--clinical needs and application.

Biomarkers for Alzheimer's disease have many diagnostic and therapeutic uses. They can be used to facilitate diagnosis, particularly early diagnosis and possibly presymptomatic diagnosis. In evaluating treatment aimed at modifying the course of AD, biomarkers can help to assess whether the drug is hitting a target or influencing disease mechanisms in the brain, and can help with dose-finding. In definitive clinical trails, biomarkers can be used as surrogate outcome measures. Progress has been made in investigating candidate biomarkers in cerebrospinal fluid and plasma. At present, cerebrospinal fluid levels of amyloid-beta, tau and phospho-tau come closest to meeting criteria proposed for useful biomarkers for diagnosis. Other biomarkers can provide insight into processes such as inflammation and oxidative damage. Unbiased and broad-based searches for novel biomarkers using proteomics have much potential. As efforts to diagnose and treat AD move towards earlier intervention and even towards prevention, biomarkers will gain significance as tools to aid research and ultimately clinical practice.