While the first blood test detecting Alzheimer’s disease made headlines last week when it landed on the market, researchers, including the test's developers, say pairing the tool with forthcoming tests may offer more accurate diagnostics.
The test was developed by C2N Diagnostics of St. Louis, and measures a protein called beta-amyloid in the blood to determine levels of the protein buildup in the brain, which can disrupt cell function. The goal is to help patients learn if they have Alzheimer’s disease more easily, as opposed to pricey brain scans and spinal taps.
C2N's test also just received CE marking from the European Union, meaning it met mandatory EU safety and health standards.
However, Oskar Hansson, professor of neurology at Lund University and consultant neurologist at Skåne University Hospital in Sweden, told Fox News in a recent phone interview that blood tests involving certain variants of another protein, tau, may prove to be even more effective in patients with clear, measurable memory impairment. In the future, both beta-amyloid and tau blood tests might be used in combination to reach optimal diagnostic accuracy, Hansson said.
Drs. Randall Bateman and David Holtzman, founders of C2N and neurology professors at Washington University School of Medicine in St. Louis, recently explained their amyloid blood test to Fox News.
“This test is quite accurate when performed by mass spectrometry for determining whether or not a person has amyloid deposition in the brain,” Holtzman wrote in an emailed statement.
“The C2N Diagnostics PrecivityAD test is a breakthrough milestone as the first blood test available to patients and doctors,” Bateman wrote.
Hansson’s team made headlines in July when part of a three-cohort study across Colombia, Sweden and Arizona found signs of the cognitive disease 20 years before anticipated symptom onset, when using Eli Lilly's blood test. The test from Lilly works by measuring the tau protein as a biomarker for the disease. The study found that about 90% of Alzheimer's dementia cases were accurately identified, though Hansson says it varied somewhat between cohorts.
Hansson said that beta-amyloid can develop at least 10-20 years before dementia onset, and it may prove problematic because it becomes a less specific marker during the symptomatic stages of Alzheimer's disease.
“When patients have mild cognitive impairment, (i.e. problems with memory but no dementia), we found that P-tau217 in blood was a stronger predictor of subsequent development of dementia than beta-amyloid, but a combination of the two markers might prove to be optimal,” he said, adding that he looks forward to combining the P-tau217 assay with the beta-amyloid assay developed by C2N in the same patient population.
Hansson expects enough data in about one to two months to then assess diagnostic accuracy when combining Eli Lilly and C2N's tests.
C2N’s test is only available by a doctor’s order and is not covered by insurance or Medicare; costing $1,250. Holtzman says the company plans to publish data on the test “very soon,” though some data is visible on the company’s website. In an analysis among 686 patients ages 60 to 91 with brain impairment and clinically suspected Alzheimer’s disease, 55% were positive for amyloid buildup by a PET scan. Meanwhile, C2N’s test came in with a 92% sensitivity in accurately identifying amyloid-positive patients, and was 77% accurate in showing negative tests.
Finally, Hansson also cited the need for developing “appropriate use criteria,” or guidance for physicians on administering the test to which patients, and when, to avoid misuse and misinterpretation of results.