Diagnostics
Disease Research Center and has facilitated several collaborative research projects related to the blood biomarkers of Alzheimer’s.
While useful in
diagnosing Alzheimer’s, MRI and PET scans can be costly tools.
While over 55 million people are estimated to be living with dementia, 60–70% of which are caused by Alzheimer’s disease, according to WHO in 2019, 75% of these dementia cases go undiagnosed worldwide. This rises to 90% in lower-middle income countries, as reported in Alzheimer’s Disease International’s World Alzheimer’s Report 2021. Researchers predict that by 2050, over 152 million individuals will have dementia, with an official diagnosis taking up to 2.8 years. However, recent developments in diagnostics have the potential to alter this situation and provide fresh hope for early detection and management.
Diagnosing Alzheimer’s Alzheimer’s has traditionally been diagnosed using a multi-step process. Doctors start by going over the patient’s medical history and using tests like the Montreal Cognitive Assessment (MoCA) or the Mini-Mental State Examination (MMSE) to evaluate cognitive function. Changes in the structure and function of the brain can be detected with the use of positron emission tomography (PET) scans and magnetic resonance imaging (MRI). For example, amyloid plaques, a defining feature of Alzheimer’s disease pathology, can be found using PET scans. Furthermore, determining the amounts of tau and amyloid-beta proteins in cerebrospinal fluid (CSF) provide vital information about how the illness develops. While these methods effectively confirm a diagnosis, they are not without their drawbacks. Neuroimaging is costly and often unavailable in resource-limited settings, while lumbar punctures for CSF analysis are invasive and uncomfortable for patients. Moreover, “Cognitive impairment can have many different causes and patients with Alzheimer’s disease brain pathology often have multiple issues that are causing or contributing to their cognitive impairment,” explains Suzanne E. Schindler, MD, PhD, associate professor of neurology at Washington University School of Medicine, who leads the Fluid Biomarker Core for the Knight Alzheimer’s
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“If we perform a thorough evaluation, we can sometimes find reversible causes that are contributing to cognitive symptoms in patients who also have Alzheimer’s disease pathology. These issues can be as simple as sleep apnoea or medication side effects. This is why it’s important not just to perform a test for Alzheimer’s disease pathology and, if positive, to attribute all cognitive symptoms to Alzheimer’s – the full diagnosis is often much more complicated.” In recent years, the discovery of biomarkers has revolutionised the understanding and diagnosis of Alzheimer’s. Amyloid-beta, tau, and neurofilament light chain (NfL) proteins are examples of biomarkers, which are quantifiable indications of biological processes, in the context of Alzheimer’s disease. These chemicals are essential to the development of the illness and are now able to be identified with previously unprecedented precision.
A step up in diagnostics
Blood-based biomarker testing is arguably the most exciting advancement in Alzheimer’s diagnoses. In contrast to conventional techniques, these tests are accessible, affordable and less intrusive, which makes them perfect for widespread screening and early detection. According to Niklas Mattsson-Carlgren, MD, PhD, associate professor at the Clinical Memory Unit at Lund University, and neurologist at the Memory Clinic, Skåne University Hospital, “Blood biomarkers are developing very strongly and are able to reach diagnostic performance which is very close to or non- inferior to what can be achieved with more expensive or invasive methods with CSF and PET.” “Accurate blood tests for Alzheimer’s disease pathology are becoming increasingly available,” says Schindler. “They provide very similar information to tests we have used in research for decades, such as sophisticated imaging scans and cerebrospinal fluid tests, but the blood tests are much easier to perform.” Phosphorylated tau (p-tau), which indicates abnormal tau protein aggregation in the brain, is one promising biomarker. Research has indicated a substantial correlation between Alzheimer’s pathology and blood levels of p-tau217. In a recent study led by Schindler, the accuracy of six commercial blood tests that measure blood levels of one or more Alzheimer’s biomarkers was compared. One of which, p-tau217, was exceptionally accurate in four of the tests that used the biomarker, meeting the standard of cerebrospinal fluid tests. Mattsson-Carlgren’s research has also outlined the promise of p-tau217, demonstrating its high accuracy in diagnosing Alzheimer’s and potential to outperform traditional diagnostic tools. Another study published in Nature Medicine by Mattsson-Carlgren et al. also found that plasma pTau 181 levels were able to
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