Blood Test Shows Promise for Alzheimer’s Diagnosis

SUSHRUT -A Magazine of Pharmaceutical Sciences

Volume 1, Issue 1, August 2024, Pages 11-13

Blood Test Shows Promise for Alzheimer’s Diagnosis

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August 2024 ➧ A MAGAZINE OF PHARMACEUTICAL SCIENCES ➧ ¹ Institute of Pharmaceutical Sciences, RKDF University, Ranchi, Jharkhand-834004, India ➧ Volume 1

Alzheimer's disease is the most common type of dementia. It is a progressive disease beginning with mild memory loss and possibly leading to loss of the ability to carry on a conversation and respond to the environment. A simple blood test shows promise as a way to detect Alzheimer’s disease, which could drastically improve the accuracy and speed of diagnoses. Currently, Alzheimer’s is diagnosed via a mixture of memory and cognitive tests, as well as brain imaging and lab tests. While some blood tests have shown promise as a diagnostic tool, they are hindered by their complexity. A simple blood test has been shown to detect Alzheimer’s disease in routine healthcare settings with up to 90% accuracy, according to Swedish researchers. The findings were presented at the Alzheimer’s Association International Conference in Philadelphia. The findings could speed up the quest for an affordable and accessible way to diagnose patients with memory problems.

: Alzheimer's disease, Alzheimer’s diagnosis, Blood test

Introduction

Alzheimer’s disease [1] is a brain disorder that slowly destroys memory and thinking skills, and eventually, the ability to carry out the simplest tasks. In most people with Alzheimer’s, symptoms first appear later in life. There is currently no cure, but there are ways to support a person through medication and other strategies. Approximately one in five women and one in 10 men develop dementia due to Alzheimer’s disease, according to the Alzheimer’s Association [2].

Common symptoms of Alzheimer’s disease include memory loss, language problems, and impulsive or unpredictable behaviour. One of the main features of the condition is the presence of plaques and tangles in the brain. Another feature is a loss of connection between the nerve cells, or neurons, in the brain. These features mean that information cannot pass easily between different areas of the brain or between the brain and the muscles or organs. As the symptoms worsen, it becomes harder for people to remember recent events, to reason, and to recognize people they know [3].

Eventually, a person with Alzheimer’s disease may need full-time assistance. Alzheimer’s disease is the most common type of dementia. It involves plaques and tangles forming in the brain. Symptoms start gradually and are most likely to include a decline in cognitive function and language ability. No disease-modifying drugs are available for Alzheimer’s disease, but some options may reduce the symptoms and help improve quality of life. Drugs called cholinesterase inhibitors can ease cognitive symptoms, including memory loss, confusion, altered thought processes, and judgment problems. They improve neural communication across the brain and slow the progress of these symptoms.

Methodology

In a study published in the Journal of the American Medical Association [4], the researchers said their new method accurately detected signs of Alzheimer’s in around 90% of patients. Researchers reported that a blood test was significantly more accurate than doctors’ interpretation of cognitive tests and CT scans in signaling the condition. Dementia specialists using standard methods that did not include expensive PET scans or invasive spinal taps were accurate 73 percent of the time, while primary care doctors using those methods got it right only 61 percent of the time. The blood test’s accuracy was highest with patients who had already progressed to dementia and was slightly lower with patients in a pre-dementia stage called mild cognitive impairment.

Results

Blood test based on the ratio of plasma phosphorylated tau 217 (p-tau217) relative to non–ptau217 (expressed as a percentage of p-tau217) combined with the amyloid-β 42 and amyloidβ 40 plasma ratio (the amyloid probability score 2 [APS2]) accurately identify Alzheimer disease in primary care and secondary care.

There were 1213 patients undergoing cognitive evaluation in primary or secondary care. The APS2 had high diagnostic accuracy (range, 88%-92%) for detecting Alzheimer disease pathology in both primary and secondary care. Dementia specialists identified clinical Alzheimer disease with a diagnostic accuracy of 73% vs 91% using the APS2 and primary care physicians had a diagnostic accuracy of 61% vs 91% using the APS2.

The patients then underwent both the blood test and cerebrospinal fluid tests, and researchers compared the results. The test works by measuring the levels of Plasma PhosphoTau217, a biomarker that is linked to the presence of Alzheimer’s pathology in the brain. By comparison, the blood test had an accuracy of 90%. The main limitation of the research was that it was only conducted in Sweden. It has been shown to detect the disease even before the person begins experiencing symptoms. The biomarker, known as plasma phosphorylated tau 217 (or p-tau217), can also be found in cerebrospinal fluid, but extracting that is a more difficult process than blood. The test also looked at the ratio of two components of a plaque that forms in the brains of people with Alzheimer’s. If the p-tau217 was found in a sample along with a certain ratio of the plaque components, the researchers theorized it would lead to conclusive evidence that a patient had the disease [5].

The APS2 and percentage of p-tau217 alone had high diagnostic accuracy for identifying AD among individuals with cognitive symptoms in primary and secondary care using predefined cutoff values. Future studies should evaluate how the use of blood tests for these biomarkers influences clinical care.

Conclusion

The new study used a blood test that focuses on a form of a protein called tau that sprouts into tangles in the brains of people with Alzheimer’s. Medical experts say the findings bring the field closer to a day when people might receive routine blood tests for cognitive impairment as part of primary care checkups, similar to the way they receive cholesterol tests. The findings could speed up the quest for an affordable and accessible way to diagnose patients with memory problems.

References

1. Williamson J, Goldman J, Marder KS. Genetic aspects of Alzheimer disease. Neurologist. 2009 Mar;15(2):80-6. doi: 10.1097/NRL.0b013e318187e76b. PMID: 19276785; PMCID: PMC3052768.
2. https://www.foxnews.com/health/alzheimers-blood-test-detects-disease-accuracy-routine-doctors-appointments-study
3. https://www.medicalnewstoday.com/articles/159442#what-is-it.
4. Palmqvist S, Tideman P, Mattsson-Carlgren N, et al. Blood Biomarkers to Detect Alzheimer Disease in Primary Care and Secondary Care. JAMA. Published online July 28, 2024. doi:10.1001/jama.2024.13855.
5. https://gizmodo.com/blood-test-shows-promise-for-alzheimers-diagnosis2000480827.