Know thy enemy! It soon may be possible for people to find out their risk for Alzheimer’s disease (AD), thanks to a new test that the FDA is expected to approve. Besides being a powerful tool for managing risk, this test should help reduce diagnostic errors when symptoms such as memory loss or confusion in a particular patient are mistakenly attributed to Alzheimer’s — a sad situation that happens 20% of the time or more, by some estimates.

Even though there is no effective cure for Alzheimer’s (and few promising ones on the horizon), approval of this diagnostic test would nonetheless be a great advance, says Norman L. Foster, MD, professor of neurology and director of the Center for Alzheimer’s Care, Imaging and Research (CACIR) at the University of Utah. At present, the only way to know, absolutely and for sure, that a person has Alzheimer’s is to wait until he/she dies and examine the brain via autopsy — which clearly is not helpful. We spoke recently about what this new test will mean for diagnosis and treatment of patients with Alzheimer’s disease.

Nearly 100% Reliable

First, let’s take a look at the test. Dr. Foster explained that a radioactive contrast dye is injected into people suspected of having AD. The dye travels to the brain. Doctors can then use a PET scanner to detect whether there are any amyloid plaques in the brain — along with other symptoms, the presence of these plaques can confirm that a person has AD. This test is considered quite safe, because the dye is similar to other agents already widely in use.

Confirmation that it works: Recent studies on living AD patients have demonstrated a near perfect (96%) correspondence between what the scans showed and what subsequent autopsies of those patients revealed, Dr. Foster notes.

What the Test Can’t Tell You

It’s important to keep in mind, however, that while amyloid PET scanning reliably detects plaques in the brain, it does not on its own provide a definitive diagnosis — doctors still must use their clinical judgment to interpret the results in the context of a person’s medical history and symptoms. It is possible to have plaques but not have the typical problems associated with AD, Dr. Foster explained. Indeed, 30% of people who have amyloid plaques do not experience memory problems. But, importantly, without amyloid plaques a person does not have AD.

What the test can tell you is the probability of Alzheimer’s:
  • A low level of amyloid plaques in the brain indicates a low risk for AD.
  • A high level suggests that a person has or is likely to develop the disease.
  • If there are symptoms (such as memory loss or dementia) and there are no amyloid plaques in the brain, Alzheimer’s can be ruled out — so doctors know to look for other causes of the symptoms (e.g., minor strokes, medication side effects or malnutrition).

This Test Can Be Used For Screening

Dr. Foster compares detecting amyloid plaques in your brain with detecting atherosclerosis in your coronary arteries. If you have plaque buildup and hardening in your coronary arteries, you are at a higher risk for heart attack and/or stroke — but that does not necessarily mean you will have one. Likewise, amyloid plaques in your brain predict a higher risk for memory problems due to AD — but you will not necessarily develop it. This leads Dr. Foster to predict that it may become commonplace within the next decade to use amyloid PET scanning to screen for AD in people who are exhibiting symptoms. He said that research is currently evaluating how accurate a predictor of the disease it truly is.

Dr. Foster anticipates that the FDA will approve amyloid PET scanning in the next few months and believes that the scans will be particularly useful when there are doubts about diagnosis. Even if the diagnosis is AD, knowing can help you plan for what lies ahead. There are medications that improve Alzheimer’s symptoms, as well as drugs to avoid if you have the disease. And it is never too late to improve your quality of life — even as the disease progresses — by taking active steps to stay mentally engaged.