Is there a test for Alzheimer’s disease?

After spending 30 minutes hunting for your car in a parking lot, or getting lost on a familiar route, have you ever considered asking your doctor for a blood test or brain scan to find out if you have Alzheimer’s disease?

A number of factors contribute to Alzheimer’s disease. By definition, this form of dementia involves the buildup of a protein in brain called beta-amyloid. Beta-amyloid forms plaques that disrupt communication between brain cells, and ultimately destroys them. For this reason, tests for Alzheimer’s disease focus on beta-amyloid.

Blood tests for Alzheimer’s disease are being developed

Recently, researchers at Washington University in St. Louis measured the levels of beta-amyloid in the blood of 158 mostly normal people (10 had cognitive impairment).

When they compared their findings with those of amyloid brain PET (positron emission tomography) scans performed within 18 months of the blood draw, they found very similar results. Moreover, the few people in their study who had a positive blood test and negative brain scan were actually 21 times more likely to have a positive brain scan in the future. This means that the new blood test may be extremely sensitive at detecting Alzheimer’s disease — that is, it results in few false negatives.

If you’re worried about your memory, should you ask your doctor for this test? Not yet — the blood test is still being evaluated and is not currently available for clinical use.

What about amyloid brain PET scans?

Maybe you’re thinking about having an FDA-approved amyloid brain PET scan. These tests involve the injection of a radioactive dye attached to a molecule that sticks to amyloid plaques in the brain. The radioactivity is then measured by special imaging technology, similar to a CT scan.

Should you get one? You could, but there are two issues to consider. First, they are not paid for by insurance — and they cost about $5,000 — so you either have to pay out of pocket or join a research study at a National Institute on Aging Alzheimer’s Disease Research Center, where you might get one for free. Second, how would the information help you?

No special amyloid brain scans are needed for the straightforward diagnosis and treatment of memory loss. If you are having significant symptoms of memory loss, such as those mentioned above, talk with your doctor about them. Your doctor will likely evaluate your overall health and the medications you take, then do some standard blood tests and brain scans as well as pencil and paper testing. Based on the results of those tests, your doctor may start you on a medication intended to boost your memory function.

Perhaps you don’t have any symptoms of Alzheimer’s disease today, but one of your parents had it. Should you get an amyloid brain scan to find out if you are likely to develop Alzheimer’s in the future?

Unfortunately, there are no medications that can prevent or slow down the development of Alzheimer’s disease. So if you get the scan and it is positive, again, what will you do with the information?

Spinal fluid tests are available now — and paid for by insurance

Perhaps I’ve convinced you that you don’t need to rush out and have an expensive amyloid brain scan. But there are situations when it is important to find out if you or a loved one has Alzheimer’s, versus another brain disease that would be treated differently. In these situations, we often use a spinal fluid test that is quite good at being able to distinguish Alzheimer’s from other brain diseases affecting thinking and memory.

To obtain the spinal fluid, you need to undergo a lumbar puncture, more commonly known as a spinal tap. Although it may sound frightening, it is actually a perfectly safe test. You simply sit or lie down on your side with your back to the doctor and curl into a little ball by bringing your shoulders down and your knees up. The doctor finds the right spot, cleans the area well, gives you some numbing medicine, inserts a thin needle, and takes out a small amount of spinal fluid, which is sent to a lab for analysis.

Exercise daily, eat right, stay social, keep active

Lastly, don’t forget that you can work to prevent Alzheimer’s disease every day by performing aerobic exercise, eating a Mediterranean-style diet, staying socially engaged, and keeping your mind active. These activities are the only things that have been proven to reduce your chances of developing Alzheimer’s disease — regardless of the results of any special tests.