Accuracy confirmed
Positron emission tomography (PET) is the gold standard in the diagnosis of Alzheimer's disease, but it is accompanied by radiation exposure to the body and is characterized by a high cost (from 5000 to 8000 dollars per scan). Another diagnostic method is to determine the level of beta-amyloid and tau protein in the cerebrospinal fluid. This study costs about $ 1,000, but requires a spinal tap, which not every patient agrees to.
Washington University Medical School in St. Louis has developed a method that allows detecting early signs of Alzheimer's disease with high accuracy from a blood sample. In an international study involving about 500 volunteers from three countries, the test reliably detected the initial signs of the disease, even if the patient himself did not complain of cognitive impairment. The test developed by Randall Bateman and his colleagues shows whether amyloid plaques have begun to form in the brain, based on the ratio of the levels of beta-amyloid proteins Aß42 and Aß40 in the blood.
Diagnostics using the new method can reduce both the cost (up to $ 500) and the time required to include patients in clinical trials that use PET scanning.
The Precivity AD test was certified in 2020 as part of the Clinical Laboratory Improvement Amendments (CLIA) program. The CLIA certification program is conducted by the FDA and the Centers for Medicare and Medicaid Services. CLIA certification makes this test available to clinicians in the United States and in Europe.
The current study shows that the blood test remains fairly accurate, even if it is carried out in different laboratories according to different protocols and in different cohorts.
The authors of the study wanted to find out whether small differences in blood sampling methods (for example, taking on an empty stomach or after eating or using different anticoagulants to preserve the material) could have a significant impact on the accuracy of the test, since its results are based on minimal shifts in the level of beta-amyloid protein in the blood. If differences in the blood sampling protocol affect the ratios of amyloid proteins, they can lead to a false negative or false positive result.
To test the accuracy of the test, the researchers used blood samples from people currently participating in large Alzheimer's disease studies in the United States, Australia and Sweden, each using different protocols for processing blood samples and related brain imaging.
The results confirmed that a blood test for Aß42/Aß40 using the precision immunoprecipitation mass spectrometry Precision AD gives accurate and consistent results for both patients with confirmed cognitive impairment and healthy people in each of the three studies.
When elevated levels of beta-amyloids in the blood were combined with another major risk factor for Alzheimer's disease – the presence of the genetic variant APOE4, the accuracy of the analysis of Precivity AD was 88% compared with PET imaging of the brain and 93% compared with spinal tap.
Thus, the test can be useful for identifying patients at risk of developing dementia in the future, which gives them hope for timely treatment. A negative test result will help doctors rule out Alzheimer's disease in patients and link their disorders to some other disease or medication.
Article Y.Li et al. Validation of Plasma Amyloid-β 42/40 for Detecting Alzheimer's Disease Amyloid Plaques is published in the journal Neurology.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of Washington University School of Medicine in St. Louis: Blood test for Alzheimer's highly accurate in large, international study.