Alzheimer’s blood test performs as well as spinal fluid tests

A study by researchers at Washington University School of Medicine in St. Louis and Lund University in Sweden shows that a blood test can be as good at detecting molecular signs of Alzheimer’s disease in the brain as cerebrospinal fluid tests approved by the Food and Drug Administration (FDA) for Alzheimer’s diagnosis.

The blood test, which was created by Washington University researchers, uses a highly sensitive technique to measure levels of Alzheimer’s proteins in the blood.

The article, titled Highly Accurate Blood Test for Alzheimer’s Disease Comparable or Superior to Clinical CSF Tests, was published 21 February in Nature Medicine.

The findings demonstrate that a blood test can diagnose Alzheimer’s disease pathology as accurately as cerebrospinal fluid tests and brain scans, even in patients with mild symptoms, and can be used to detect molecular signs of Alzheimer’s disease in the brain when symptoms haven’t yet emerged.

“The accuracy of this blood test now enables us to diagnose the presence of Alzheimer’s disease pathology with a single blood sample,” said co-senior author Randall J Bateman, MD, the Charles F and Joanne Knight Distinguished Professor of Neurology at Washington University. “This advance will increase accurate diagnoses for many patients.”

“In the near future, this type of blood test will replace the need for costly and less accessible cerebrospinal fluid and PET imaging tests in specialist memory clinics,” said co-senior author Oskar Hansson, MD, PhD, a Professor of Neurology at Lund University. “Next, we need to determine if the Alzheimer’s blood test also works in primary care. This is currently being investigated in Sweden.”

The blood test is based on the effects of amyloid accumulation on tau protein. The presence of amyloid in the brain changes the levels of various forms of tau protein in the brain and in the blood. Measuring the ratio of phosphorylated tau-217 (ptau-217) and unphosphorylated tau in the blood reliably reflects brain amyloid levels. A test combining the amyloid and tau blood measures is marketed by the Washington University startup C2N Diagnostics, as PrecivityAD2.

Th study compared the abilities of four tests to identify people with amyloid in their brains: the ptau-217 blood test and three FDA-approved cerebrospinal fluid tests. Both groups included people with very mild and mild cognitive symptoms, as well as healthy people for comparison. The tests’ accuracy rates were calculated by comparing their results to the gold standard: PET brain scans for amyloid and tau tangles.

The ptau-217 blood test was just as good as the FDA-approved cerebrospinal fluid tests at identifying people with amyloid buildup, with accuracy scores for all tests at 95% to 97%. In a secondary analysis, the researchers measured how well the tests determined the levels of tau tangles in the brain. In this, the ptau-217 blood test was superior to cerebrospinal fluid tests, with accuracy scores in the range of 95% to 98%.


  • Barthélemy NR, Salvadó G, Schindler S, et al. Highly Accurate Blood Test for Alzheimer's Disease Comparable or Superior to Clinical CSF Tests. Nat Med. Published online February 21, 2024. doi:10.1038/s41591-024-02869-z


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