While medical experts have long disputed what’s behind the development of Alzheimer’s disease, they all agree that a simple, affordable diagnostic test is long overdue.
Up until now, the most accurate way to diagnose Alzheimer’s disease has been through an invasive and uncomfortable lumbar puncture (spinal tap) or an expensive PET scan. Labs around the world have been racing to develop a simple blood test that’s as good as or better.
After many years of work, scientists from Sweden think they’ve finally achieved success with a “game changer” blood test.
If this sounds familiar, it should. Over the last year we’ve reported on a number of different studies investigating blood markers that can indicate the development of Alzheimer’s disease. These markers have included Ptau217, Ptau181 and neurofilament light (NfL).
Ptau217 and Ptau181 are two of a long list of tau proteins abundant in brain cells. When they undergo chemical changes, these proteins are strongly linked to Alzheimer’s disease. NfL is also a protein. It’s found in nerve fibers and has recently been linked to a wide range of neurological diseases including Alzheimer’s disease.
Now, a new study published over the summer suggests there’s yet another blood marker that can indicate Alzheimer’s disease—it’s called NT1.
The Higher NT1, the Worse Memory Declines
NT1 measures fragments of tau secreted by brain neurons in response to amyloid pathology. You may recall that amyloid beta plaques have been found in the brains of Alzheimer’s patients. Some experts believe that these plaques prevent healthy communication between brain cells, but other experts dispute that and point to research showing amyloid beta plaques in healthy, Alzheimer’s-free brains.
Now, back to NT1…
Scientists from Boston found that blood levels of NT1 can accurately predict future cognitive decline in clinically healthy elderly participants. In fact, they found that the greater the levels of NT1, the worse the cognitive decline four to six years later. They also found that levels of NT1 correlate with levels of NfL. In other words, patients who had high levels of NT1, also had high levels of NfL.
Experts believe blood markers such as these are the future of Alzheimer’s diagnosis. For one thing, they think these blood markers hold the key to revealing whether patients are suffering from normal age-related memory loss or a memory-robbing illness.
Alzheimer’s Disease Versus Mild Cognitive Impairment
Mild Cognitive Impairment (MCI) can present a challenge to clinicians trying to diagnose Alzheimer’s disease. If the loss of memory is more than would be expected from normal aging, a person may be diagnosed with MCI.
With MCI, memory changes aren’t severe. The activities of normal daily life are not significantly affected. Some patients with MCI will never get any worse, while a few will actually improve. However, many will go on to develop Alzheimer’s disease and it’s this group that doctors desperately want to identify as early as possible.
Doctors haven’t been able to tell which patients will progress to Alzheimer’s disease but advances in blood marker research are changing that. We’ve reported before on the research team from Lund University in Sweden that has spent years analyzing different blood markers including Ptau181 and NfL. They’ve made an amazing discovery.
Alzheimer’s Predicted Four Years Early with 89 Percent Accuracy
Scientists at Lund University studied 573 people with MCI who had an average age of 71. They took blood samples, ran cognitive tests and then waited to see who progressed to Alzheimer’s four years later.
What they discovered was that blood testing for Ptau181 and NfL could predict with 89 percent accuracy those patients who would progress from MCI to Alzheimer’s. The blood testing could also predict with 88 percent accuracy those patients who would not progress to Alzheimer’s disease.
Lead researcher Oskar Hansson reported, “Our goal over the last few years has been to find simple methods that can be used in primary care to make an early diagnosis and to begin treatment to relieve symptoms at an earlier stage. This will require more studies, but we have absolutely come one major step closer to our goal.”
While the findings excited many neuroscientists, not all memory experts believe that blood markers are the Holy Grail of Alzheimer’s diagnosis.
Mixed Opinions Among Experts
Masud Husain, professor of neurology at the University of Oxford, was the most enthusiastic, saying, “This is a potential game changer. We need further validation but in the context of other recent findings this could be a transformative step to earlier diagnosis, as well as testing new treatments at earlier stages of the disease.”
Dr. Richard Oakley, head of research at the Alzheimer’s Society, was also upbeat, saying “…if these blood markers can predict Alzheimer’s in larger, more diverse groups, we could see a revolution in how we test new dementia drugs.”
However, other doctors were more muted with their comments.
Neuroscientist John Hardy, from University College London (UCL), described the discovery as “welcome, but not an unexpected finding.”
His UCL colleague, psychiatrist David Curtis, could only say that it “provides some additional knowledge.”
Several others pointed out that because huge numbers of people are diagnosed with MCI, even the admittedly “impressive” sensitivity of the test would still leave “considerable” levels of misdiagnosis.
Accuracy and Specificity is Important
In July, we first reported on how the presence of Ptau217 could predict the onset of dementia years before the earliest symptoms of the disease. So, it’s important to point out those findings.
Other testing for Ptau217 was able to distinguish patients with Alzheimer’s rather than other forms of dementia with even more accuracy—96 percent accuracy—making it a highly specific test and certainly more specific than testing for NfL and Ptau181 together or alone.
More study on all of the known blood markers for Alzheimer’s disease is certainly needed, however, the results of the latest scientific investigations are very exciting.
The thought of being able to get a simple blood test to determine if common memory lapses are due to aging or Alzheimer’s disease—or something else— will be life-changing.
I have no doubt that one day soon a combination of these blood markers will be established as the new testing gold standard for diagnosing Alzheimer’s disease years before symptoms begin.