Neurologists diagnose cognitive impairment with a clinical exam of memory and thinking skills. To determine whether Alzheimer’s disease is the cause of the cognitive impairment, evidence of the specific brain changes that characterize Alzheimer’s must be obtained, typically via a brain scan or spinal tap. Identifying people whose cognitive symptoms are due to Alzheimer’s disease is critical now that new Alzheimer’s therapies are available that could change the course of the illness.
To make diagnosis more convenient for patients, many companies have begun selling Alzheimer’s blood tests to consumers, and at least five companies are now offering these tests to doctors for clinical use. Doctors have no way of knowing which tests are most accurate because, until now, the tests have not been evaluated in a head-to-head comparison using the same population, methods and criteria.
Suzanne Schindler, MD, PhD, and her team at Washington University School of Medicine in St. Louis led a data analysis comparing the accuracy of six commercial blood tests, four of which are clinically available, in detecting signs of Alzheimer’s disease, particularly the presence of the characteristic amyloid plaques in the brain. The analysis showed that some of the tests are accurate enough to replace spinal taps and brain scans in many patients with cognitive impairment. The head-to-head comparison was part of a project developed and launched by the Foundation for the National Institutes of Health Biomarkers Consortium, a public-private partnership of which Washington University is a member. The results were presented July 30 in an oral session at the Alzheimer’s Association International Conference in Philadelphia.
“Some of the blood tests are accurate and some are not, and doctors don’t know which tests to use,” said Schindler, an associate professor of neurology at Washington University and the lead author of the study. “With this head-to-head comparison, doctors now have more reliable information about which tests will best help them provide an accurate diagnosis to their patients.”
Confirming that cognitive impairment is due to Alzheimer’s disease — early in the course of the illness — is crucial for ensuring access to the newest generation of Alzheimer’s therapies. In the past two years, the Food and Drug Administration (FDA) has approved two drugs that slow the trajectory of disease, with more in the pipeline. Both FDA-approved drugs target amyloid, so doctors must confirm that a patient has amyloid buildup in the brain before they can prescribe the treatment. In addition, the diagnosis must be confirmed as early in the disease course as possible, because the drugs are only approved for people with very mild to mild symptoms.
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.