A biological marker (biomarker) is a measurable substance in an organism whose presence is indicative of some phenomenon such as disease or infection. Biomarkers can help doctors and scientists diagnose diseases and health conditions, find health risks in a person, monitor responses to treatment, and see how a person's disease or health condition changes over time.
Biomarkers can show early indications of biological changes associated with Alzheimer’s disease (AD). AD may begin causing gradual changes in the brain some 10-20 years before the onset of symptoms.
The best hope of stopping AD is before symptoms appear, and the need for earlier treatment makes biomarkers so important.
Biomarkers and Alzheimer’s Disease
Scientists are searching for an “AD signature” using biomarkers. Said another way, scientists are looking for earlier signs of AD that aren’t visible to the naked eye by studying many types of biomarkers. In the future, a biomarker test could:
- Allow for a proper clinical diagnosis earlier before symptoms are visible.
- Provide reliable measures of how the disease progress in a particular patient.
- Guide treatment decisions. When drugs become available, determining such things as who needs treatment, when to start, and which drugs and treatment strategies are most likely to be successful.
- Be used by doctors to monitor response to treatment.
It is now widely accepted that distinct subtypes of Alzheimer’s exist. Biomarkers may help distinguish between these different types of the disease and help inform optimal patient-specific treatment options.
What types of biomarkers are being studied?
In Alzheimer's and other forms of dementia, primary biomarkers are toxic proteins associated with the disease – like amyloid-beta and tau. These can be detected using neuroimaging scans such as PET or MRI, or by testing the cerebrospinal fluid or more recently, blood.
The goal is to find the least invasive, earliest measures that might be able to detect the probability of disease. More novel biomarker assessments are being developed that use the eye to detect changes in the brain as well as driving or walking patterns that may serve as earlier detectors of disease.
- Biomarkers in Cerebral Spinal Fluid (CSF)
- Biomarkers in Blood
Biomarkers in Cerebral Spinal Fluid (CSF)
CSF is a clear fluid surrounding the brain and spinal cord and functions as a cushion, protecting the brain. It is also an optimal source of AD biomarkers, like proteins. Proteins that are made in the brain are released into the CSF and measuring them provides great insight into events and changes taking place within the brain. CSF can be safely collected by a procedure called a lumbar puncture (spinal tap).
Biomarkers in Blood
Thanks to donors who support our Alzheimer’s Disease Research program, BrightFocus provided key, early funding to develop the first-ever blood test to diagnose Alzheimer’s through a blood sample. The PrecivityAD™ blood test is now in use in the United States and Europe, helping to boost early diagnosis and speed recruitment into clinical trials.
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Explore More of Our 360° Research Approach
- Tangling with Tau
- Battling Amyloid Beta
- Blood and the Brain in Dementia
- Immunity and Inflammation
- Biology of APO E and Lipids
- Cell Death
- New Approaches
Genes are the “master blueprint” that instructs our cells to make unique proteins which in turn build, operate, and repair human tissue. Humans have an estimated 24,000 genes along our 23 matched pairs of chromosomes (46 in all), and “genomics” refers to the field that studies all of them at once.
Tangling with Tau
Tau is a small protein with a short name but a large reputation because of its association with multiple brain diseases, including Alzheimer’s disease (AD). The tau protein is predominantly found in brain cells (neurons).
Battling Amyloid Beta
There are many versions of amyloid protein in the human body, and most serve a useful role. One of the hallmarks of Alzheimer’s disease (AD) is the accumulation of amyloid plaques (abnormally configured proteins) between nerve cells (neurons) in the brain.
Blood and the Brain in Dementia
Scientists are interested in developing a screening tool for Alzheimer’s disease (AD) in blood. A simple blood draw is much less invasive than a spinal tap and may prove more cost effective. Developing blood biomarkers that accurately depict brain changes has proven challenging, as levels of AD hallmark proteins in the blood are low, but there are some very recent promising results observing tau and the ratio of Aβ42 and Aβ40.
Immunity and Inflammation
One theory about Alzheimer’s disease (AD) is that it may be triggered, in part, by a breakdown in the brain’s immune system.
Biology of APO E and Lipids
Alzheimer's disease (AD). Its primary function is to regulate a class of proteins involved in the metabolism of fats (lipids) in the body. However, APOE has several common variants (or "alleles") whose effects vary.
The human brain has an estimated 100 billion neurons. Extending from each of them is a long fiber, known as an “axon,” which can run several feet. Each axon forms a connection, known as a “synapse” with another neuron, creating a circuit over which brain signals travel. In Alzheimer’s disease (AD), individual neurons die and do not regenerate; while others have brains that are more are resilient and respond to meet changing demands.
Years of innovative and dedicated research have paid off with the discovery of numerous factors contributing to Alzheimer’s disease (AD) pathology. With a disease as complex as this one, it’s very helpful to find multiple points where it may be possible to slow or halt its progress.