As a practical matter, the tests are not widely available. They involve special procedures such as spinal taps and PET (positron emission tomography) scans and can cost thousands of dollars. Most doctors are not yet familiar with the tests or confident of their reliability. Moreover, Medicare and other insurers don't generally cover these tests to diagnose Alzheimer's. Still, some experts may use them as part of a larger evaluation for dementia. Some patients also may get the tests in clinical trials.
For now, the recommended evaluation for people with symptoms still rests on talking with the patient and family, administering memory and other mental function tests, and running blood tests and basic brain scans designed mainly to rule out other conditions such as a stroke or tumor. (There are also genetic tests for early-onset Alzheimer's, a rare form of the disease that occurs in people under 65.) Writers of the new guidelines say doctors can usually diagnose Alzheimer's accurately using these traditional methods.
But an Alzheimer's test for some patients with troubling memory loss could be coming soon. Eli Lilly's Amyvid, an injectable radioactive dye that stains amyloid deposits to highlight them on PET brain scans, may be the first Alz heimer's diagnostic product on the market. The U.S. Food and Drug Administration has signaled a willingness to approve it — if the company can ensure those who read the scans are trained to give accurate, standardized results.
The drugmaker says Amyvid would be for older people with mental decline whose diagnosis is uncertain.
Over the years, many doctors have wondered what good could come from telling a patient he might have Alzheimer's, a largely untreatable disease. This attitude, however, is changing, with experts increasingly advocating early diagnosis. They argue that the standard evaluation might instead find a treatable cause of mental confusion — such as depression — and that, even without an effective treatment for Alzheimer's, getting a diagnosis before the disease becomes disabling gives patients time to make choices about how to cope with it.
Another reason to promote early diagnosis: Most Alzheimer's researchers believe that when we find an effective drug, it will almost certainly need to be used early, before damage accumulates in the brain. Indeed, the new guidelines now define a first stage of Alzheimer's, when changes begin in the brain but mental symptoms have yet to develop.