Multiplexing Biomarker Methods, Proteomics and Considerations for Alzheimer's Disease.

Biomarker research for Alzheimer's disease (AD) has been growing rapidly over recent years especially as the number of persons affected by this disease is nearing approximately 46 million worldwide. Single biomarker assays are challenging to establish since AD is multifactorial and complex. In addition to the classic signs of diminished cognition and memory, AD patients can also exhibit symptoms which may be confused with some psychiatric disorders, such as depression. No molecular biomarkers have been established or translated into clinical tools although recent efforts have resulted in addition of molecular biomarker profiles to the National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer's Disease and Related Disorders Association criteria for research purposes. The three accepted molecular biomarkers are amyloid-βeta peptide 1-42, total tau protein and hyperphosphorylated tau at threonine 181 in human cerebrospinal fluid (CSF). Aside from these three CSF markers, a number of potential candidates have been identified in CSF and other body fluids. In order to identify biomarkers for diagnosis, early prevention, prognosis and response to therapeutic treatment, multiplex biomarker tests will be required. These include multiplex immunoassay and mass spectrometry-based proteomics platforms. Proteomics analyses of bodily fluids such as plasma are growing in number and providing potential targets for further investigation and validation in AD research. This chapter highlights proteomic biomarker assays and their applications and potential use for clinical diagnosis and prognosis of AD.