Diagnosis Critical To Early Intervention
Alzheimer’s disease is typically diagnosed through a combination of symptoms and guesswork. It’s far from a science. Testing is primarily done through brain imaging and behavioral tests, which are costly and often fail to detect the disease in its earliest stages. However, research shows a promising blood test that may detect Alzheimer’s disease before symptoms appear.
The first blood test designed to assist physicians in determining whether a patient has Alzheimer’s disease is now available in most US states. The test measures biomarkers that frequently reflect the presence of amyloid plaques in the brain—a hallmark of Alzheimer’s disease—as well as the presence of a gene variant that increases the risk of the disease. Independent experts are leery because key test results have not been published and the test has not been approved by the U.S. Food and Drug Administration. The test is being sold under rules for commercial labs. It also should be able to confirm Parkinson’s disease, which has the same pathology as Alzheimer’s disease. The primary difference is that Parkinson’s impacts a different region of the brain than Alzheimer’s disease.
“It’s not a cure, it’s not a treatment, but you can’t treat the disease without being able to diagnose it,” said Alzheimer’s disease researcher Dr. Michael Weiner.
The blood test from C2N Diagnostics of St. Louis aims to fill that gap. The company’s founders include Drs. David Holtzman and Randall Bateman of Washington University School of Medicine, who headed research that led to the test and are included on a patent that the university licensed to C2N.
Only doctors can order the blood test and results come within 10 days. It’s sold in all but a few states in the U.S. European regulators just approved the test.
The test costs $1,250, says C2N CEO Joel Braunstein, but patients who qualify for financial assistance will be charged between $25 and $400. Health insurance companies don’t currently pay for the test. The best way now to measure the protein is a costly PET brain scan that usually is not covered by insurance. That means most people don’t get one and are left wondering if their problems are due to normal aging, Alzheimer’s or something else. The PET brain scan costs some people about $5,000 and often isn’t covered by insurance.
“I’m very excited about it,” says Suzanne Schindler, a neurologist at the Washington University School of Medicine in St. Louis who was involved in testing an earlier version of the assay but is not connected to C2N. While there are two other tests for Alzheimer’s-associated brain changes, she notes, both have logistical and financial challenges: one that collects biomarkers in the cerebrospinal fluid (CSF) requires a spinal tap, while the other, a scan called amyloid PET, involves injecting a radioactive tracer, costs thousands of dollars, and is only performed at specialized centers. “I think patients really like the idea of a blood test,” she says.
Being able to distinguish Alzheimer’s disease from other possible causes of cognitive impairment is valuable. Earlier diagnoses can’t stop the disease, but treatments can prolong the period before people lose the ability to function on their own.
Symptom-based diagnosis of Alzheimer’s disease is only about 70 percent accurate, notes Colin Masters of the Florey Institute of Neuroscience and Mental Health in Australia who was part of the team that first characterized the amyloid plaques in the disease. If a clinician suspects the disease but the blood test returns a negative result, this “will force the clinicians to go and look harder for other causes of dementia,” says Masters, who collaborates with one of the test’s developers but has no ties to C2N. He adds that once an amyloid-targeting Alzheimer’s drug is approved, the test will be useful in determining who should receive it.
Now, the bad news. Amyloid plaques are forms of prions–infectious proteins (the contagion). As the new blood test confirms, infectious prions are in the blood of those who have prion disease (Alzheimer’s disease, Creutzfeldt-Jakob disease, and Parkinson’s disease, for example). Blood banks have not been screening for prions in the blood. Blood transfusions, surgical instruments, dental tools and many other prion pathways have been ignored. Once exposed to infectious prions, these tools are permanently contaminated. To contain prion disease and the prion pandemic, we must manage all prion pathways. Blood pathways are just the tip of the iceberg.
