New Blood Test Can Detect Alzheimer's Before Symptoms Occur

Nov 1, 2017

Credit Arizona State University

November is National Alzheimer’s Awareness Month.  The neurodegenerative disease affects over five million people in the United States.  That number is expected to grow to 16 million by 2050.  With no cure and no long term treatments, new studies are focused on early detection.  This year, researchers discovered a way to detect Alzheimer’s even before the onset of symptoms in people at genetic risk for developing the disease.  

Difficulty completing tasks, confusion with time or place and problems speaking or writing can be early obvious symptoms of Alzheimer’s disease. 

“We’ve known for some time that Alzheimer’s disease starts damaging the brain decades before it’s clinically diagnosed.” 

Paul Coleman is a Research Professor at the Biodesign Institute at Arizona State University.   

“One of the reasons why the clinical trials that have been tried so far have failed so routinely is probably that by the time somebody comes to clinical diagnosis, and entered in the clinical trial, the brain is so damaged that it’s pointless to treat this disease.  It’s kind of like pouring gasoline into a car that has no engine.”

Coleman and his colleagues hope they’ve found a way to identify the disease’s onset before clinical symptoms.  They’ve developed a low cost, non-invasive blood test that can determine the risk of a future diagnosis of Alzheimer’s.

“Basically the way it works is we look at the expression of about a half a dozen genes in the blood cells.”

Alzheimer’s produces changes in the brain that can stimulate genes related to stress and inflammation. Expression of these genes appears in the blood in the form of specific RNA transcripts.  Authors of the study say these RNA transcripts can be combined into a potent early diagnostic or biomarker, which can be used to distinguish healthy patients from those with Alzheimer’s or Parkinson’s disease and make accurate predictions about people at risk of developing Alzheimer’s disease in the future.

“Many people think of stress and inflammation as being one-size fits all.  There are a lot of flavors or varieties of inflammation and there are a lot of different molecules that are related to inflammation and stress that can distinguish Alzheimer’s and Parkinson’s disease.”

The blood testing can accurately identify those carrying two APOE4 genes, a major genetic biomarker for late-onset Alzheimer’s disease.  In the study, transcript screening was also used to identify at least one direct relative with AD.  It also used two different RNA analysis techniques and was able to distinguished probable Alzheimer’s disease from normal controls with an accuracy of 93.8 percent.

“So while it does detect Alzheimer’s reasonably well, the point really is that it detects risk for future diagnosis of Alzheimer’s disease.”

Authors of the study hope the test can detect the disease early enough that drugs which have failed in clinical trials may succeed in helping those in the early stages of Alzheimer’s.  Dr. Mark Stacy is a neurobiologist and the Dean of East Carolina University’s Brody School of Medicine.   He was a leader for clinical research for neurodegenerative diseases at Duke University before coming to the Brody School of Medicine in Greenville last month.  

“We have medications right now that are not highly effective for Alzheimer’s disease but they work really well in people with a little more than just mild cognitive impairment.  So to be able to provide patients with medications at a time when they’re really helpful would be great.”

A simple, minimally invasive blood test could replace costly and invasive methods for helping diagnose Alzheimer’s such as PET scans, MRI and spinal taps and would allow trials for new drugs targeting at-risk patients to ramp up significantly.  Some are calling this a potential breakthrough for prevention and treatment of Alzheimer’s disease.  But there’s still a lot more testing that needs to be done. And, no one really knows how the blood test with potentially quality of life changing results should be administered. There’s the potential for an at-home blood test, similar to home genetic testing, but Dr. Stacy questions if that’s the best option.

“When you see the commercials on TV, people say well I thought I was German and it turns out I’m not.  That’s a whole lot different than I thought I had normal cognition and turns out I have Alzheimer’s disease.”

Dr. Stacy believes the blood test is a tool that without context could be devastating to someone living an otherwise normal life.  That’s why he supports point of testing at a doctor’s office where the results can be explained in detail. Research Professor at the Biodesign Institute at Arizona State University Paul Coleman imagines the blood testing being widely accessible, similar to an annual flu shot. 

“Somebody goes to the drugstore and gets a test and the test comes back and tells them that they’re probably going to get Alzheimer’s or they’re at high risk for Alzheimer’s, how do you treat that person, what do you do with that person, I mean that’s a, to many people that would be a very shocking piece of information.”

Coleman admits the results of the blood test can be confusing to interpret.  Just because Alzheimer’s is detected, Dr. Stacy says it doesn’t mean that it will develop. 

“If your blood test fits an array that looks like you’re going to develop Alzheimer’s disease, you have a risk of developing Alzheimer’s disease, but it doesn’t guarantee that you’re going to get it.  So if it causes you to make life altering decisions and you don’t get Alzheimer’s disease, that would be unfortunate.”    

Then, there’s also the question of when the test should be administered.

“So we have to be very careful with the risk of diagnosing someone with Alzheimer’s disease when they’re 18 and they’re not going to have symptoms until they’re 68.  So that’s one of the caveats that I worry about with potential diagnostic testing.”

The recent study from Arizona State University was published in the journal Neurobiology of Aging.