A blood test approved by the Food and Drug Administration in May provides an inexpensive and noninvasive way to detect biomarkers of Alzheimer’s disease, vastly increasing opportunities for early detection and treatment.

“It makes things much easier for both patients and physicians,” says Abhay Moghekar, associate professor of neurology at the Johns Hopkins University School of Medicine. “New medications are now available to treat Alzheimer’s disease, but they are only effective if it is diagnosed early, and early diagnosis depends on having accurate biomarkers.”

The test, known as the pTau217/ß-Amyloid 1-42 Plasma Ratio, is FDA approved for patients who are 55 or older and have been medically assessed as experiencing cognitive decline.

It was developed based on research completed at Johns Hopkins, Lund University and private companies.

Moghekar’s lab contributed important data and validated the test against the results from cerebrospinal fluid (CSF) biomarkers already approved by the FDA. “They pooled subjects from three studies to come up with this test,” he says. “We contributed many of the samples and did the testing of those samples here in our lab.”

The test is now being rolled out for primary care physicians and specialists to order through their electronic medical record systems, says Moghekar, with commercial diagnostic laboratories in the process of acquiring the necessary kits to process the results.

Moghekar says the test, which finds plasma biomarkers that indicate amyloid pathology, does not deliver a definitive diagnosis, but instead provides an amyloid range. Patients with scores over the high-end cutoff have more than a 90% likelihood of having Alzheimer’s disease, while patients below the low range almost certainly do not have it.

About 20% of those tested will fall in the intermediate category, he says, requiring additional testing from neurologists or gerontologists supported by supplemental PET scans and CSF testing to reach a confident diagnosis.

Before the Alzheimer’s disease blood test, amyloid buildup could be detected through PET scans of a patient’s brain, or by analyzing cerebrospinal fluid for signs of abnormal amyloid. Both techniques are invasive, expensive and require specialized equipment and personnel, Moghekar notes.

Moghekar says funding from the National Institutes of Health has made advances in Alzheimer’s disease detection and care possible. “The last decade or so has seen a big boost from the NIH National Institute on Aging,” he says. “That’s helped the field, and that’s why we’re seeing these breakthroughs.”

He believes this blood test is just the beginning. Other researchers are developing tests that detect tau, the tangles that indicate a more advanced disease state. The two tests together could provide earlier, more definitive diagnoses, and also help in staging the disease, he says.

For more than two decades, Moghekar has been part of a longitudinal study, led by neurology professor Marilyn Albert, of one of the world’s longest-running, deeply phenotyped cohorts for Alzheimer’s research. Some 300 participants are flown to Johns Hopkins each year for evaluations that include repeated CSF and blood sampling, along with detailed neurocognitive testing, MRI scans and PET scans.  

Despite the time-consuming and invasive commitments, more than 90% of the original group remains, Moghekar says. About three-quarters are participating because they have experienced Alzheimer’s in their own families, he says.  

Participants were enrolled when they were in their mid-50s and healthy. Now, they are in their late 70s and early 80s, and about a third have some cognitive impairment, says Moghekar. “We can now compare people who have progressed to people who have not progressed to find the earliest signs of disease,” he says.

It appears that a discrepancy between amyloid production and the brain’s ability to clear it begins for many people when they are in their 40s or 50s, he says.

“Our ultimate goal,” he says, “is to prevent Alzheimer’s disease, not treat it once you have it.”