Modern Medicine

Alzheimer's blood test detects disease decades before symptoms, aiding drug search

Key Points
  • Alzheimer's remains a deadly and incurable disease that affects 5.5 million Americans.
  • It is one of the greatest threats to the solvency of Medicare.
  • New blood tests can identify patients up to 20 years before physical symptoms.
  • This could prove crucial in developing preventative treatments.

Every 66 seconds someone in the United States develops Alzheimer's. The disease is debilitating and deadly. Day-to-day tasks become difficult or impossible. Caregivers sacrifice untold time and energy to keep patients safe and comfortable.

A woman with Alzheimer's performs a memory exercise in a nursing home.
Getty Images

Researchers have yet to find a drug that reverses the effects of Alzheimer's once they start to show, and the repeated failures have been crushing. But two recent studies on blood tests might help turn the tide by helping develop more effective treatments.

Researcher Dr. Randall Bateman of Washington University in St. Louis unveiled a blood test this past summer that can detect Alzheimer's decades before a patient shows physical symptoms. Then this past January a Japanese and Australian team published a study in Nature about a blood test that can detect Alzheimer's with 90 percent accuracy.

A key characteristic of Alzheimer's is the buildup of a protein called amyloid beta in the brain. This toxic protein can cause dementia. Amyloid has been the overwhelming target of clinical drug trials in the Alzheimer's field. Bateman estimates the blood test can detect amyloid up to 20 years before a person will develop Alzheimer's.

The blood tests use mass spectrometry to detect amyloid beta. Dr. Koichi Tanaka, a Nobel Prize-winning chemist, first developed mass spectrometry testing for proteins, and he was instrumental in the Japanese/Australian study.

"The Japanese group independently developed a similar mass-spectrometry assay and found nearly identical findings to ours," Bateman said via email to CNBC. "This indicates the test is repeatable and robust, even in different labs."

The current alternatives to the blood test are invasive and expensive. One alternative is a lumbar puncture, or spinal tap, to collect cerebrospinal fluid. The procedure requires local anesthetic before a doctor inserts a needle between two vertebrae in the lower back. The other alternative is a positron emission tomography, or PET scan, which can cost $7,000 or more. PET scans only detect amyloid betas with 20 percent to 30 percent accuracy.

"A blood test is the quickest, easiest and fastest way, and it's certainly the cheapest way," said Dr. Robert Vassar, an Alzheimer's researcher at Northwestern University. "If we could do a blood test, that would make things a lot simpler."

The next step is a preventative treatment

With no effective cure for Alzheimer's, and drugs designed to slow the onset continuing to fail, the 5.5 million Americans already living with Alzheimer's face a devastating future. Even though the blood test can't help these patients, it will put the $1.4 billion in federal research money for Alzheimer's — still significantly less than funding for cancer and heart disease — to good use.

If doctors can easily and effectively catch Alzheimer's in its early stages, they can enroll patients in experimental trials for preventative treatments. The more asymptomatic patients doctors can identify early and put in trials, the sooner researchers can develop preventative treatments. A lack of qualified patients for clinical trials has been cited by Dr. Jeff Cummings of the Cleveland Clinic, a leading authority on Alzheimer's trials, as one of the the primary reasons for the widespread drug-trial failures.

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Amyloid betas are a ticking time bomb in the brain, and the need for an effective preventative treatment is crucial for those at risk. Northwestern's Vassar uses the analogy of a trigger on a gun. Amyloid betas are the trigger, and twisted protein fibers, called tangles, are the actual bullets that kill. As amyloid betas build up, the trigger gets pulled, and tangles start destroying the brain. New therapies might be able to slow or stop the trigger.

"There might be a point of no return," Vassar said. He equates Alzheimer's to heart disease. Doctors don't give statin drugs to patients who are already in heart failure, and some medications won't work for Alzheimer's patients whose brains are already showing deterioration.

The importance of the blood tests will grow once preventative treatment is identified. "Then we will desperately need a simple screening test to identify those at risk and also help accurately diagnose those with symptoms," Bateman said.

A blood test is the quickest, easiest and fastest way, and it's certainly the cheapest way," said 
Dr. Robert Vassar
Alzheimer's researcher at Northwestern University

Heart disease deaths have actually decreased 14 percent since 2000, while Alzheimer's deaths have increased 89 percent. Of the diseases listed in the 10 leading causes of death in the United States, Alzheimer's is the only one that can't be prevented, slowed or cured. The Alzheimer's Association estimates that the number of Americans with the disease could reach 16 million by 2050. Alzheimer's patients live for years after a diagnosis, and the necessary expensive care might drain Medicare in the future if there is no preventative treatment or cure.

Dr. Christopher Van Dyck, a Yale University Alzheimer's researcher, is excited about the blood tests ability to streamline experimental testing, but he knows there is still a ways to go. "This is not yet ready for the clinic, but it could be with further independent validation," he said.

Tanaka and Bateman are both working on new studies to advance blood testing. Bateman hopes the test will be readily available to the public within a few years.

— By Rick Morgan, special to

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