Finding a biomarker in Alzheimer’s disease (AD) that translates into clinical meaningfulness has been a real challenge for the field of biomarkers in the central nervous system (CNS). The current way to definitively diagnose AD is through brain scans and tests of cerebrospinal fluid (CSF) that must be collected via lumbar puncture, but these procedures are invasive and expensive.
The lumbar puncture procedure is very invasive as it requires local anesthetic before a doctor inserts a needle between two vertebrae in the lower back, while a positron emission tomography (PET) scan, which is very expensive, can only detect amyloid betas in the brain with 20% to 30% accuracy.
These challenges created opportunities for biomarkers that can be measured by simple blood or urine tests at point-of-care. Researcher at UNT Health Science Center in Fort Worth developed a test that will find biomarker proteins in the blood to detect AD.
The trial, funded by a $6.5m grant from the National Institute on Aging, is now ongoing to prove the effectiveness and accuracy of the test in people 65 years or older who are experiencing memory issues; it will take three years before having full results. The test could be easily administered in a primary care physician’s office, with better accuracy compared to PET scan and a far cheaper cost, disrupting the expensive and invasive scanning and spinal fluid technologies.
There is a great unmet need for simple, inexpensive, and non-invasive tests that could be applied on a large scale to screen for AD. The current testing process for AD involves a lot of steps, such as a physician’s visit, further referral to a specialist, and a magnetic resonance imaging (MRI) or PET scan that is not reimbursed and very expensive. This process could take months, and blood tests in development for AD could satisfy this need with accuracy close to 90% and replace CSF testing and brain imaging.
Challenges of implementing a new Alzheimer’s blood test
A major challenge impacting the development of blood-based biomarker tests is the blood-brain barrier (BBB), which functions to create a protective barrier around the brain and limits the flow of substances in or out of the CNS. It is quite difficult to determine whether peripheral measures of putative biomarkers are actually representative of what is going on within the section of the brain and CNS enclosed by the BBB. This difficulty has limited the development of biomarkers to a level where they can have clinical utility.
However, even without treatments being available, there is a value for patients and their families in obtaining an accurate diagnosis of AD, which could allow them to plan for their future, make lifestyle changes that could help prevent rapid disease progression, start symptomatic treatments earlier, or even make the decision to enroll in a clinical trial of AD treatments in development.
If physicians can easily and effectively detect AD in its early stages, they can enroll patients in experimental trials for preventative treatments, as lack of qualified patients for clinical trials is one of the primary reasons for drug-trial failures in AD. Having patients more carefully evaluated and referred to specialists who can administer more complex cognitive exams or utilize the latest diagnostic biomarker tools can confirm an AD diagnosis and enable researchers to develop preventative treatments that are most likely to be effective.