A biomarker is a physical, biochemical, or functional measure used as an indicator of a physiological change or disease process. Biomarkers—sometimes referred to as surrogate markers or clinical endpoints—can be used to define, diagnose, or predict disease and enable rational treatment and monitoring of disease. Basic mechanistic studies of specific disorders can identify molecules in biological fluids, tissues, or even breath with which disease-related changes could be identified as disease biomarkers. Biomarker imaging tools such as positron emission tomography (PET), magnetic resonance imaging (MRI), and nuclear magnetic resonance (NMR) spectroscopy scans can reveal detailed alterations in tissue due to disease processes and permit non-invasive longitudinal tracking of disease progression. Other biomarkers help determine cognitive declines through standardized neuropsychological test batteries or the effect of environmental triggers or social stress factors on aging and health outcomes. Some biomarkers can also predict susceptibility to disease or serve as measures of drug toxicity.
There is a critical lack of specific, reliable, quantifiable, and easily measured biomarkers that correlate well with early disease progression. Public and private organizations have invested heavily in identifying candidate disease biomarkers using technologies such as imaging, genomics, proteomics, and high-throughput approaches. NIA-supported initiatives help to refine technologies for biomarker discovery and apply them to specific diseases. The Alzheimer’s Disease Neuroimaging Initiative, for example, seeks to identify whether longitudinal and concurrent brain imaging and biochemical measurements can be used to monitor disease progression. Improved brain imaging promises to provide researchers with the ability to monitor how drugs affect the accumulation of harmful proteins as disease progresses. Biological samples from well-characterized patients enrolled in this and similar studies are made available for other investigations.
NIA is working to improve the precision and validity of biomarkers for monitoring the progression of other diseases such as osteoarthritis or assessing an individual’s risk of cardiovascular disease or diabetes. Advanced biomarker technology also promises to streamline clinical trials by identifying clinical subtypes to establish more homogeneous study populations and applying biomarker testing to monitor and assess the effects of trial interventions.