Biomarkers

What is a biomarker?

A biomarker (also known as a biological marker) is something that helps measure a normal biological process, a disease or response to a treatment³⁴.

Why are biomarkers useful in early stage Alzheimer’s disease?

Biomarkers may be used to identify people who are at risk years or even decades before symptoms appear. One of the most important goals of neuroscience research is to develop and validate biomarkers that can detect and identify disorders early²².

Today, progress is being made in developing biomarkers relevant to Alzheimer’s drug development, especially those that characterize disease progression³⁵.

Facts about biomarkers to detect prodromal Alzheimer’s disease

The quest for biomarkers for Alzheimer’s disease includes research in multiple fields: biochemistry, genetics and genomics, structural and functional imaging and neurophysiology²².

Different biomarkers assess different biological processes in different parts of the body, providing complementary information. Different biomarkers have different sensitivities and predictive abilities; they can also have a different role at different stages of the disease. For example, cerebrospinal fluid (CSF) biomarkers and imaging biomarkers relating to beta-amyloid show great promise for diagnosing patients before they show symptoms³⁶.

Amyloid-beta and tau are among the most promising and informative Alzheimer’s disease biomarkers³⁶. Most patients with mild cognitive impairment who later progress to develop Alzheimer’s have decreased beta amyloid and increased tau in the CSF³⁷.

Combinations of biomarkers may be valuable. Recent studies suggest that a combination of CSF tau and amyloid-beta (Aβ) biomarker changes may predict whether a person with mild cognitive impairment will eventually develop Alzheimer’s – and possibly heralds disease onset before clinical symptoms emerge³⁷.

Amyloid in the brain can be detected using ‘markers’ of amyloid, such as the Pittsburgh compound B (PiB), a specific marker that measures amyloid-beta³⁸.

Research suggests that patients with Mild cognitive impairment who have positive PIB scans are highly likely to progress to Alzheimer’s disease; whereas those with negative scans are not³⁵, suggesting that PiB identifies mild cognitive impairment patients who do not yet meet criteria for dementia in the early phases of Alzheimer’s disease.

Developments are underway to try to develop biomarkers in blood but as yet these are not available.

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