As it happens, to find out what is going on in the brain of someone with Alzheimer’s disease, all it takes is a drop of blood. Unimaginable only three years ago, researchers now have plasma biomarkers that correlate with amyloid plaques, neurofibrillary tangles, and neurodegeneration—the three major neuropathological hallmarks of AD. So rapidly has the science progressed that C2N Diagnostics, a company that grew out of basic biomarker research at Randall Bateman’s lab at Washington University, St. Louis, recently gained certification for its Precivity mass-spec Aβ assay. In the U.S., regulators at the Centers for Medicare & Medicaid Services approved the test under the Clinical Laboratory Improvement Amendments protocol. CLIA certification is a prerequisite for any laboratory testing of human samples outside of research settings. The EU gave the test its own CE Mark of approval for in vitro diagnostic medical devices.
- C2N’s mass-spec for plasma Aβ gains CLIA and CE approval.
- The company has begun marketing the test to patients and doctors.
- Plasma p-tau181 and p-tau217 are nipping at its heels.
Developers of plasma phospho-tau assays are nipping at C2N’s heels. Recent publications and meeting presentations bolster the evidence that upticks in p-tau181, p-tau217, and p-tau231 occur soon after Aβ begins to accumulate in the brain. That’s years before neurofibrillary tangles can be detected by PET, and decades before symptoms. Researchers predict these markers, which also distinguish AD from other forms of dementia, will lead to more robust tests than those based on Aβ, because of their larger dynamic range—phosphorylated fragments of tau climb by as much as 10-fold in the blood as AD progresses, whereas the Aβ42/40 ratio falls by about 15 percent at most.
Nevertheless, researchers applauded C2N’s milestone. “The development of a CLIA-certified blood test to help characterize the presence or absence of amyloid plaques and return information to clinical providers, patients, and families in the clinical setting is an important landmark,” wrote Eric Reiman, Banner Alzheimer’s Institute, Phoenix. “It is my hope that we will see other assays, including plasma p-tau217, follow in the footsteps of this effort, and provide additional value to those in the research, treatment development, and clinical setting,” he added (see comment below). Reiman co-founded ALZPath, a company planning to develop plasma p-tau217 and other blood-based biomarkers for use in research, drug development, and clinical care.