Alzheimer's blood test diagnosis clears hurdle

A new blood test that detects Alzheimer's disease has successfully passed an initial regulatory hurdle, researchers said Monday.

The blood test could eventually be used to diagnose Alzheimer's in its earliest stages, leading to treatment that could delay the onset or progression of the disease, according to a study published in the journal Genome Biology.

Alzheimer's, the most common form of dementia, is characterized by the loss of memory and other cognitive abilities serious enough to interfere with daily life.

Researchers from Germany's Saarland University focused on microRNAs (miRNAs), small molecules of genetic material that circulate in bodily fluids and impact gene expression. They analyzed 140 miRNAs both in patients with Alzheimer's disease and in healthy people, and found that levels of 12 miRNAs were markedly different in the blood of people with Alzheimer's.

The test, conducted on 202 people, was accurate 93 percent of the time, according to the study.

An estimated 5.2 million Americans have Alzheimer's, with numbers expected to increase as the U.S. population ages. By 2025, the number of people aged 65 and older with the illness is expected to grow by 40 percent unless a cure or preventive treatment is found, according to advocacy group The Alzheimer's Association.

Alzheimer’s is the sixth leading cause of death in the U.S., according to the Alzheimer's Association. Alzeimer's deaths increased by 68 percent between the years of 2000 and 2010.

A primary goal of Alzheimer’s research is to find ways of detecting the disease before its onset. Presently, the illness can only be diagnosed with certainty at autopsy, according to the Saarland University study. 

The illness is typically diagnosed by using cognition tests and brain scans after symptoms have emerged, the study said. The identification of reliable and non-invasive biological markers has remained a major challenge for researchers seeking to treat Alzheimer's. A successful blood test, then, would be a marked advance.

Researchers caution that the blood test still needs to undergo clinical trials before it can be used to diagnose patients.

"Only a number of individuals have been tested so further studies would be needed to verify this," said Dr. Dean Hartley, a spokesman for the Alzheimer's Association. "We always like to encourage research in this area because it could lead to earlier detection of the disease."

"Alzheimer's becomes more complicated to treat once it has progressed," he added. "Developing earlier detection methods helps with developing treatment to slow or stop the progression of the disease."

Putting the miRNA blood tests through clinical trials would be very useful for monitoring the progression of the disease, Dr. Hartley said. That's because clinical trials would not only seek to identify genetic biomarkers for Alzheimer's, but would also look at how they're affected by treatment and whether there are any secondary effects.

The Saarland University study builds on prior Alzheimer's studies which have focused on miRNAs as effective blood-based biomarkers for the identifying many different diseases, including cancer and certain brain disorders, Dr. Hartley said.

Amel Ahmed contributed to this report.