On Jul. 30, 2024, a head-to-head comparison of six commercially available blood tests for Alzheimer’s disease led by researchers at Washington University School of Medicine in St. Louis has revealed that two are accurate enough to replace brain scans and spinal taps in some patients with cognitive impairments.

A newly developed blood test for Alzheimer’s disease not only aids in the diagnosis of the neurodegenerative condition but also indicates how far it has progressed, according to a study by researchers at Washington University School of Medicine in St. Louis and Lund University in Sweden. Several blood tests for Alzheimer’s disease are already clinically available, including two based on technology licensed from WashU. Such tests help doctors diagnose the disease in people with cognitive symptoms, but do not indicate the clinical stage of the disease symptoms – that is, the degree of impairment in thinking or memory due to Alzheimer’s dementia.

Current Alzheimer’s therapies are most effective in early stages of the disease, so having a relatively easy and reliable way to gauge how far the disease has progressed could help doctors determine which patients are likely to benefit from drug treatment and to what extent. The new test can also provide insight on whether a person’s symptoms are likely due to Alzheimer’s versus some other cause.

The team evaluated the ability of six commercially available blood tests to detect proteins in the blood that correlated with key features of Alzheimer’s disease: amyloid plaques and tangles of the protein tau in the brain, reduced brain volumes and cognitive impairment. The six tests were developed by ALZpath, C2N Diagnostics, Fujirebio Diagnostics, Janssen, Quanterix and Roche Diagnostics. C2N Diagnostics is a Washington University startup, and its Alzheimer’s tests are based on technology licensed to C2N by the university.

Blood samples and participant data were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), a long-running, multisite collaboration designed to identify Alzheimer’s biomarkers and to advance biomarker development by sharing data and resources within the research community. The study included 392 people who had provided blood samples within six months of undergoing brain scans. The participants had a median age of 78.1 years, and just under half (49%) exhibited cognitive impairment.

Each of the six tests measured the blood levels of one or more biomarkers linked to Alzheimer’s disease. Across the six tests, five distinct biomarkers were measured using various techniques. One biomarker, used in four of the tests, proved exceptionally accurate at identifying signs of Alzheimer’s disease: a form of tau known as phosphorylated tau 217 (p-tau217).

The four tests that incorporate measures of p-tau217 all performed well, regardless of the approach they took to measuring the protein. The top two performers across all measures were C2N Diagnostics’ PrecivityAD2 and Fujirebio’s Lumipulse. The study was published in Nature Medicine.