Blood Test for Alzheimer's Disease? New Findings

Alzheimer's disease is difficult to diagnose as the symptoms may be similar to other neurological disorders such as Lewy body disease, vascular dementia, and even Parkinson's disease. At present, clinicians rely on PET scans and CSF testing. Wouldn't it be easy if we had blood tests to diagnose Alzheimer's disease? Here are some significant findings from recent research.

Key takeaways:

Dementia is a group of symptoms where people experience difficulties with memory, language, problem-solving, and judgment. Approximately 60–80% of persons with dementia are diagnosed with Alzheimer's disease. However, neurological diseases such as vascular dementia, Lewy body disease, and frontotemporal dementia may have dementia as a symptom. This makes accurate diagnosis of Alzheimer's disease a challenge for clinicians.

Diagnosing Alzheimer’s disease

In 2023, the Alzheimer’s Association report estimated that 6.7 million Americans are suffering from dementia. This number will double by 2050, and the U.S. will experience a shortage of clinicians who can diagnose the disease. Some areas will become ‘dementia neurology deserts,’ meaning they will not have enough neurologists to serve the general population.

The report also estimates that, currently, 85% of patients with dementia were initially diagnosed by their primary care physician, and 40% of the physicians did not feel comfortable making a diagnosis of Alzheimer’s or other forms of dementia. An objective criterion (e.g., findings from a brain scan) would help when making a diagnosis. Having an easy-to-administer blood test would be useful in early and accurate diagnosis of Alzheimer’s disease.

Misdiagnosis of Alzheimer's disease

Early diagnosis of Alzheimer's disease can help patients and their families plan their future. However, approximately 70% of persons with Alzheimer's disease are misdiagnosed at primary care facilities. At present, to receive a diagnosis of Alzheimer's disease, patients must undergo extensive testing such as cognitive testing, cerebrospinal fluid (CSF) testing, and PET scans. This testing may not be available at primary care facilities, and patients must travel to the hospitals that provide specialty care.

Furthermore, approximately 30% of the patients with Alzheimer's disease in specialty care are misdiagnosed as they may not be able to undergo testing. For instance, patients who take anticoagulants are not well suited for lumbar puncture. Patients who do not have insurance or the means to pay for PET scans may decline the scan. These situations highlight the need for an affordable and effective blood biomarker test for detecting Alzheimer's disease.

Possible blood biomarkers for Alzheimer's disease

Certain proteins that are characteristic of a specific disease pathology when present in the blood serve as blood biomarkers of that disease. For instance, Amyloid beta or Aβ42/Aβ40 can be found in the CSF and brain tissue of persons with dementia.

But can we find these proteins in the blood?

Researchers have tried to study the plasma Aβ42/Aβ40, but these biomarkers show a small difference between amyloid-positive and negative individuals. Hence, initial tests using plasma samples could not detect Alzheimer’s disease with certainty. Another possible blood biomarker is tau protein. However, tests have not yet detected this protein with certainty.

Clinical trial with promising results

PharmaKure is a U.K.-based company spun out of the University of Manchester, and it focuses on the treatments of neurodegenerative diseases such as Alzheimer's disease. The company has developed an Alzheimer’s disease biomarker test called ALZmetrix. A clinical trial was conducted at the Glasgow Memory Clinic to determine the accuracy of the test.

The study examined the relationship between biomarker proteins in patient blood and tests performed as current standard care, i.e., PET scans and CSF tests. After the approval of the Institutional Review Board, 54 subjects participated in this study. Along with the clinical data, the study considered other predictors of disease such as age, gender, tau protein, and genetics using machine learning algorithms.

The results of the study indicate that the ALZmetrix blood test can identify patient groups that are amyloid-positive or amyloid-negative with 97% accuracy. This ability to detect amyloid protein in the blood helps in predicting patients at the highest risk of Alzheimer’s disease. As the disease advances, tau and p-tau proteins can be detected in the blood. ALZmetrix test can also detect tau protein and, hence, preliminary results indicate that the test can track the progression of the disease.

The results are not yet published in peer-reviewed scientific journals, but the company has shared the results of this novel test with the public. The company will conduct studies with large sample sizes that meet regulatory requirements before the test is commercially available in healthcare facilities. This innovative test can facilitate testing for Alzheimer's disease at smaller clinics instead of large hospitals.

The final word

In summary, Alzheimer's disease is often misdiagnosed in its early stages due to the lack of tests that are easy to administer. A blood biomarker test can help in diagnosing Alzheimer’s disease. PharmaKure, a company spun off from the University of Manchester, U.K., developed a test to detect amyloid proteins in the blood. This test, when commercially available, will be useful to diagnose Alzheimer's disease in early stages. Stay tuned as we regularly publish further updates on biomarkers of Alzheimer's disease at Healthnews.

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