Goodbye spinal tap? A simple blood test to detect Alzheimer’s disease

Until recently, screening for Alzheimer’s disease has required a lumbar puncture to collect cerebrospinal fluid and/or a PET scan to identify the presence of two biomarkers characteristic of the disease, beta-amyloid peptide and tau protein, the accumulation of which in neurons begins years before the appearance of the first symptoms. But now, a blood test could replace these cumbersome and expensive examinations.A study recently published in the journal JAMA Neurology shows that a blood test, already available, is just as effective. “What is impressive about our results is that the precision of this blood test is equivalent to that of cerebrospinal fluid analyzes and brain scans in revealing the pathology of Alzheimer’s disease in the brain,” says one of the study’s lead authors, Nicholas Ashton, professor of neurochemistry at the University of Gothenburg, Sweden.According to Ashton, “80% of individuals could be diagnosed based on a blood test without any further investigation.” Since it’s impossible to perform lumbar punctures and PET scans on everyone in the world who needs them, “that’s where the enormous potential of this blood test lies.” The study looked at data from 786 people, aged 66 on average, who'd undergone brain scans and lumbar punctures, as well as blood samples. They came from three distinct cohorts: one in the U.S. (Wisconsin Registry for Alzheimer’s Prevention or WRAP), one in Spain (Sant Pau Initiative on Neurodegeneration or SPIN) and that of the Research Center for Studies on Aging of the McGill University, Biomarkers of Aging and Dementia Cohort (BioVie).The researchers compared the results of the examinations of the three cohorts with those of a blood test developed by the Californian company ALZpath. Called ALZpath pTau 217, this test measures concentrations of a particular form of the tau protein, P-tau217, in plasma. The latter is already used as a biomarker for Alzheimer’s disease in cerebrospinal fluid, since it increases beta-amyloids and tau protein at the same time.A test marketed soonUltimately, ALZpath pTau 217 displays accuracy rates of 96% for identifying elevated levels of beta-amyloid and 97% for detecting tau protein. Only about 20% of participants had blood results that, in a clinical setting, would have required additional imaging testing or a lumbar puncture because they were unclear. “This is a significant reduction in expensive and in-demand tests,” says Ashton. Therefore, “we believe that a blood test and a clinical examination can lead to a definitive decision in 80%” of people who show early signs of dementia.For his colleagues at the University of Goteborg, Kaj Blennow and Henrik Zetterberg, “this is a breakthrough discovery for blood biomarkers of Alzheimer’s disease, paving the way for the clinical use of the ALZpath pTau test. 217,” adding that “this robust test is already used in many laboratories around the world.”“The test, known as ALZpath Dx, is currently available as a laboratory developed test (LDT) for clinical diagnostic use and clinical trials,” read a recent press release from the U.S.-based ALZpath Inc.This article was translated from its original French and was first published in our sister publication Profession Santé.

Goodbye spinal tap? A simple blood test to detect Alzheimer’s disease

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