PHILADELPHIA, July 28, 2024 — Data from three research studies, reported today at the Alzheimer’s Association International Conference® (AAIC®) in Philadelphia, suggest that highly accurate blood tests for Alzheimer’s disease are moving closer to use in doctor’s offices. These tests could revolutionize the accuracy of diagnosis and provide a faster path to treatment.

“Blood tests, once they (a) are confirmed in large populations to be more than 90% accurate and (b) become more widely available, show promise for improving, and possibly redefining, the clinical trial recruitment process and the diagnostic work-up for Alzheimer’s,” said Maria C. Carrillo, Ph.D., Alzheimer’s Association chief science officer and medical affairs lead. “While at this time doctors in primary and secondary care should use a combination of cognitive and blood or other biomarker testing to diagnose Alzheimer’s, blood tests have the potential to increase the accuracy of early diagnoses and maximize the opportunity to access Alzheimer’s treatments as early as possible for better outcomes.”

Blood Test Can Improve Diagnosis Among Primary Care and Alzheimer’s Disease Specialists

A large study led by researchers at Lund University in Sweden, reported at AAIC and simultaneously published in the Journal of the American Medical Association, shows that a blood test can do a better job of accurately detecting Alzheimer’s than both primary care doctors and specialists using traditional diagnostic methods.

In the study, funded in part by the Alzheimer’s Association, 1,213 patients were tested with PrecivityAD2 (also called APS2), a blood test that measures ratios of tau and amyloid proteins.

  • Among 698 patients seen at memory clinics, the test was approximately 90% accurate at identifying Alzheimer’s disease while specialists were 73% accurate.
  • Among 515 patients seen in primary care, the test was also approximately 90% accurate while primary care physicians were 63% accurate at identifying Alzheimer’s.

“Notably, these were the results of blood samples that have been shipped bi-weekly for analysis from primary care units, which is similar to routine clinical practice,” said lead author Sebastian Palmqvist, M.D., Ph.D., at Lund University, Lund, Sweden.

Senior author Oskar Hansson, M.D., Ph.D., also at Lund University, adds. “We see this as a major step towards global clinical implementation of an Alzheimer’s blood test. It highlights the need for Alzheimer’s biomarkers in making a correct diagnosis more of the time.”

Research Shows Blood Tests Could Identify People for Prevention Trials

A study, also from Lund University in Sweden and funded in part by the Alzheimer’s Association, reported at AAIC found that specific blood tests could identify people without cognitive impairment who likely have amyloid-beta plaques in their brains. Identifying people who have the plaques that are a hallmark of Alzheimer’s but do not have any symptoms of the disease could be useful for clinical trials. Specifically, these people could be recruited for trials of treatments or other interventions designed for use before the onset of Alzheimer’s disease symptoms.

The researchers analyzed samples from 2,718 cognitively unimpaired people across 10 different studies who had available blood tests as well as either an amyloid-beta PET imaging scan or cerebrospinal fluid (CSF) samples. They found that levels of plasma p-tau217 (from a blood test) can positively predict (with a range of 79-86%) the likelihood that a cognitively unimpaired person would also test positive for amyloid-beta plaques on an PET scan or CSF test.

“If these numbers hold up and are replicated and confirmed by other independent labs, this approach may reduce the need for lumbar punctures and PET scans for Alzheimer’s diagnosis by 80 or even 90 percent,” said Gemma Salvadó, Ph.D., lead author of the study and an associate researcher at Lund University. “Our results support that plasma p-tau217 positivity alone may be sufficient as a selection of cognitively unimpaired, amyloid-positive participants for many clinical trials.”

Blood Tests Could Drastically Reduce Wait Times for Alzheimer’s Diagnosis and Treatment

There are now FDA-approved treatments that can slow the progression of Alzheimer’s, but they require confirmation that people have amyloid-beta plaques in their brains before use. There are, however, lengthy wait times to get that confirmation due to the limited number of Alzheimer’s specialists and variable access to PET imaging or CSF analysis. Research from a study at University of Southern California, Los Angeles, reported at AAIC 2024, suggests that using blood tests in primary care could identify people eligible for the new Alzheimer’s treatments much earlier.

The researchers used a well-established forecasting model to predict wait times for people eligible for treatment. The model included the projected U.S. population of people 55 and older from 2023 to 2032 and compared two scenarios. The first was that primary care doctors would decide whether or not to refer a patient to an Alzheimer’s disease specialist based on the results of a brief cognitive test. The second was that they would also factor in the results of a high-performance blood test and assume that a blood test would be given to individuals testing positive for early-stage cognitive impairment in primary care and referrals to specialty care would be informed by the test results.

The model suggests that by 2033, people will wait an average of nearly six years (70 months) to understand if they could be eligible for new Alzheimer’s treatments if their primary care doctor only used brief cognitive assessments to make referrals. If blood tests were used to rule out Alzheimer’s, the average wait times would be reduced to 13 months for Alzheimer’s patients because far fewer patients would need to see a specialist. Researchers also determined that if blood tests and brief cognitive assessments were used at the primary care level to rule in the possibility of an Alzheimer’s diagnosis, wait times to understand eligibility for new treatments would fall to less than six months on average because of reduced demand for Alzheimer’s specialists and the additional capacity now available for CSF or PET testing.

“Our results suggest using blood tests to identify potential candidates for treatments could make a significant difference in treating people with early Alzheimer’s,” said Soeren Mattke, M.D., D.Sc., lead author of the study and director of the Brain Health Observatory, at the University of Southern California, Los Angeles. “Currently, eligible patients are falling outside of the treatment window because it takes so long to receive a diagnosis. An easy-to-use blood test could help address that problem.”