In Your Blood: The Rise Of Blood Testing For Alzheimer’s

For a while now, we’ve been tracking progress toward the development of blood tests to determine whether someone has Alzheimer’s disease. In the last several weeks, that progress has moved forward with the FDA approval of 2 new blood tests to help sort through whether someone has evidence of the hallmarks of Alzheimer’s in their blood. While neither of these tests can make a definitive Alzheimer’s diagnosis by themselves, they will, in combination with clinical assessments and other testing, help sort through whether someone who is experiencing cognitive impairment can be diagnosed with Alzheimer’s and thus be potentially eligible for new medications now available, which may slow the progression of the disease. Given that between 2000 and 2024 deaths due to Alzheimer’s jumped 134%, it is an urgent matter for individuals, their families, and the country as a whole that we do all we can to lessen the burden and mortality caused by Alzheimer’s.

The first blood test recently approved is called Precivity AD2, which was developed by researchers at Washington University School of Medicine. What makes this blood test unique is that it has been approved for use in patients as young as 40 years old who have cognitive symptoms that could be the result of Alzheimer’s. It is only intended for individuals who are already experiencing certain worrisome cognitive symptoms, not those who are well but worried about future risk. It is not a screening or stand-alone test, and it is to be used in conjunction with other clinical assessments. The blood test has been demonstrated to be effective in detecting the plaques that are the hallmark of Alzheimer’s in a wide range of patient ages, sexes, and among those with various comorbidities. Its accuracy in detecting amyloid plaque biomarkers from a blood test is over 90%, comparable to the use of a spinal tap or PET scan, which are more costly and invasive. With this level of accuracy and ease of testing, it is likely that those who may have Alzheimer’s will be diagnosed sooner and be able to access new and future therapeutic options more quickly than they would have been able to if they were awaiting a spinal tap or MRI. For more on Precivity, read here and here.

In addition to Precivity, the FDA also just approved a new test from Roche, working in collaboration with Eli Lily, to produce a blood test called Elecsys® pTau217. As with Precivity, this Elecsys blood test is only to be used in people who are already experiencing cognitive symptoms, and it is not a test that can conclusively diagnose Alzheimer’s on its own. Unlike Precivity, the Elecsys test is only intended to be available for people aged 55 and older, but the benefit of this test is that it can be run on over 4500 diagnostic machines around the country, in addition to machines run by Quest Diagnostics, so that testing can be done and analyzed with a relatively quick turnaround, all over the country. Similar to Precivity, the Elecsys test is considered highly accurate and reliable, but given the number of machines that can run the analysis, it will be relatively easy to scale up to serve the number of people who may be eligible for the test. Given estimates that up to 75% of people living with dementia are never formally diagnosed, the wide availability of this test might jumpstart the opportunity for millions of people to access potentially beneficial therapies. 

Both of these tests, as well as two prior tests that have been FDA-cleared, can help significantly improve the diagnostic process for determining if someone has Alzheimer’s, and can potentially relieve those who test negative on their blood test for Alzheimer’s biomarkers of having to go through more expensive and invasive testing. However, these tests cannot tell a patient or caregiver whether a patient instead has vascular dementia or Lewy body dementia. But they are a reliable and accurate method for ruling in or ruling out Alzheimer’s. These tests also help relieve the pressure of getting into the offices of specialty caregivers and neurologists, who previously were the only ones who could use testing to determine if a patient has Alzheimer’s. Making these tests more widely available for use by primary care physicians will help relieve some of the difficulties of determining whether a patient with cognitive impairment has Alzheimer’s. FDA approval of these blood tests may also lead to insurance coverage. For a recent guide on available blood tests for Alzheimer’s, their cost, and where you can access them, roll up your sleeve and click here.

Will we ever see therapies for those who do not yet have cognitive impairment but perhaps may be at higher risk, due to genetic markers, family history, or the presence of plaque in their brains as determined by blood tests? Well, according to a recent article in The Guardian, clinical trials to develop such therapies are now underway, with the goal of one day actually preventing dementia from even starting. An international research trial is underway that is enrolling middle-aged adults who are deemed to be at higher risk of developing Alzheimer’s. Known as the PrevenTRON study, this clinical trial will test the drug Trontinemab, which has been shown to clear out amyloid plaques in the brains of early-stage patients. If this trial were to be successful in those who have not yet developed cognitive symptoms, we might then be on the precipice of a new era of prevention rather than treatment for Alzheimer’s. This trial is anticipated to take 4-6 years for completion and analysis. For more on this exciting possibility, stay tuned.