Preventive Medicine for Neurodegeneration on the Rise: New Breakthrough in Routine Blood Testing for Alzheimer’s Disease

With neurodegenerative diseases on the rise, there’s an urgent need for early detection methods for large-scale screening. Current methods like spinal puncture for cerebral spinal fluid (CSF) and Positron Emission Tomography (PET) are highly invasive and expensive, limiting their widespread use.

To address this need, the first Alzheimer’s blood test was developed in the laboratory of Randall Bateman at Washington University and entered clinical use in December 2020. The test measures the ratio of two forms of amyloid protein in the blood and identifies the form of apolipoprotein E, a major risk factor for Alzheimer’s disease. Since then, Nicolas Barthelemy in Bateman’s lab has further developed a better test that can measure specific tau proteins in the blood. This new method, which combines tau testing with amyloid testing, is now being used in general clinics to screen patients. While research is ongoing and the test has not yet been approved by the FDA, preliminary results suggest it may be as accurate as, or even more accurate than, CSF tests.

Blood Tests: The Key to Mass Preventive Screening for Alzheimer’s Disease

Given the urgent need for quick Alzheimer’s diagnosis and the limitations of spinal tap and amyloid PET tests, blood tests are expected to become the primary method for detecting Alzheimer’s brain changes in the coming years. Drawing blood is a simple procedure, making Alzheimer’s blood tests an ideal screening tool for the majority of patients with cognitive issues. Extensive blood testing is essential for identifying the vast majority of patients with early symptoms. While these tests are currently mainly used by cognitive neurologists, they are likely to become more widespread in primary care as they become better validated and clinicians gain more knowledge about them.

In the next few years, there may be another significant shift. Clinical trials are currently assessing whether medical professionals can prevent or delay Alzheimer’s progression in individuals with normal cognition but early brain changes. If successful, primary care doctors could incorporate blood tests into annual follow-up clinics to screen older adults with normal cognition for signs of Alzheimer’s disease brain changes in its early stages. This would transform Alzheimer’s disease into a chronic health management issue akin to high cholesterol, rather than the devastating illness it is currently perceived as.

Currently, there are at least 16 blood tests for Alzheimer’s in various stages of development. While some are highly accurate, others still need improvement. Accurate blood tests could revolutionize Alzheimer’s diagnosis, making it feasible to screen large numbers of patients early in the disease’s progression. This would enable timely initiation of treatments like lecanemab, potentially slowing the disease before significant cognitive decline occurs. 

Spinal Taps are Invasive and PET Scans are Costly

Alzheimer’s disease is a progressive neurological disorder that primarily affects memory and thinking. It is the most common cause of dementia in individuals over the age of 65. Alzheimer’s is characterized by the deposition of amyloid plaques in the brain, which can be detected 10 to 20 years before the onset of symptoms. The disease progresses from mild cognitive impairment to severe dementia, impacting daily activities such as dressing, bathing, and eating.

In 2012, the U.S. Food and Drug Administration (FDA) approved amyloid PET scans, which can identify amyloid plaques in the brain. These plaques are believed to initiate a cascade of brain changes leading to dementia, and are essential in facilitating whether subjects may develop Alzheimer’s. The IDEAS study, which performed 20,000 amyloid PET scans across the U.S., highlighted the demand for such tests, given the large number of potential Alzheimer’s patients. However, although amyloid PET scans are a reliable diagnostic tool, they are costly, around $6,000, and limited in availability, making it impossible to effectively popularize it.

A further advance in the diagnostic capabilities for Alzheimer’s came more recently in 2022, with the approval and use of CSF tests. By 2022, the FDA approved tests for Alzheimer’s disease that measure amyloid proteins in CSF. Neurologists have used CSF tests for over a decade to diagnose Alzheimer’s, but the procedure involves spinal taps, which can be daunting for patients. In this regard clinicians say that many patients will not take CSF for fear of invasive testing, and patients may assume that a positive CSF test will not change their treatment regimen and therefore choose to continue with their existing medication pattern. Hence, although there are indeed effective and accurate diagnostic tools that can be used to test for Alzheimer’s, their high cost and invasive nature make them impractical for widespread use.

Lecanemab and Donanemab: Promising Therapies, but Memory Clinics Seek Enhanced Diagnostic Solutions

On July 6, 2023, the FDA fully approved lecanemab, a treatment that clears amyloid plaques from the brains of patients with mild Alzheimer’s symptoms, thereby slowing cognitive decline. Another similar treatment, donanemab, has shown promise in clinical trials. With nearly 150 treatments currently under study, there is hope for more effective therapies in the future. 

Given the effectiveness of treatments like lecanemab in the early stages of Alzheimer’s, timely diagnosis has become crucial. Memory clinics, which used to perform a handful of spinal taps per month, have increased the number of procedures significantly to meet the rising demand for early diagnosis. However, the time-consuming nature of spinal taps and the expense of PET scans necessitate more accessible diagnostic tools. Here, blood tests are expected to become the primary diagnostic tool within a few years, given their ease of use and ability to be integrated into routine healthcare. This shift would allow for widespread screening and early intervention, possibly transforming Alzheimer’s disease management from a devastating diagnosis to a chronic condition that can be managed more effectively.

Article Reference: https://www.scientificamerican.com/custom-media/davos-alzheimers-collaborative/blood-tests-for-alzheimers-could-become-routine/ 

Author

Bernice Lottering