Biofluid Biomarkers Aid in Diagnosing and Developing Improved Treatments for People with Alzheimer's Disease

Dementia is a disease in which daily life is disrupted by a loss of cognitive function. Late-onset Alzheimer's disease (AD) is the most common dementia that largely begins to affect individuals in their mid 60s or older. AD was selected as the focus of this paper because it is the most common form of dementia, accounting for 50-70% of dementia cases. A typical diagnostic approach used by physicians starts with a simple clinical test, the Mini-Mental State Examination (MMSE), when cognitive decline is suspected in a patient. Then if there is enough evidence to suggest AD, a physician would order tests for positron emission tomography (PET) or magnetic resonance imaging (MRI). While useful, the problem with these tests is that they tend to be used when cognitive decline is advanced and reflect changes in the brain that likely began 10-20 years before diagnosis. In addition, current medications can only slow but not stop or reverse cognitive decline. Thus, studies are also focused on the use of biofluid markers that may be detected earlier in the disease. Biomarkers show promise in measuring cognitive decline, while being less expensive than imaging tests. Thus, as amyloid beta fragment 1-42 (AB1-42) and total tau (t-tau) have been heavily researched among several biomarkers these will be discussed within this paper, as well as newer biomarkers including phosphorylated tau (p-tau), neurofilament light (Nfl), synaptosome-associated protein of 25 kDa (SNAP-25), microRNA (miRNA), and extracellular vesicles (EVs).