New test added to Alzheimer's research arsenal
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February 18, 1998
Billie Showers has had Alzheimer's for 15 years
Web posted at: 11:26 p.m. EST (0426 GMT)
WASHINGTON (CNN) -- A study in the New England Journal of Medicine says that researchers have identified a test that reduced false diagnoses of Alzheimer's disease by approximately 30 percent.
The test focuses on a gene known as the Apo E4 gene, and although the researchers found that it is "strongly associated with Alzheimer's disease," they cautioned that it alone is not sufficient to be used as a diagnostic tool.
However, they also concluded that using the test along with others, including an MRI, would be helpful to physicians trying to make clinical diagnoses on different types of dementia.
"Everyone inherits an Apo E gene," says Dr. Creighton Phelps of the National Institute on Aging, "one from your mother and one from your father. This gene helps predict whether you are going to have certain diseases."
Phelps says that those with the E4 gene (there are also E2 and E3 genes) are likely to get certain diseases. The researchers say the presence of the E4 form of the Apo E gene is found most often in people who exhibits signs of the disease after the age of 65.
Although the test for the E4 gene alone is not a good predictor of diseases, Phelps says "we cannot underestimate the usefulness of increasing a physician's confidence in diagnosing a disease of this magnitude.
"When facing a family who must bear the weight of such devastating news, most doctors would appreciate as many tools as possible to help them in their certainty of diagnosis. Apo E is such a tool."
False-positives drop from 45% to 16%
"People are not used to having a physician or anyone else say, 'We think you have a 90 percent chance of the disease,'" says Dr. Steve DeKosky of the Alzheimer's Association. "Their immediate answer is 'I don't wanna know that. Do I have it, yes or no?'"
Data for the study was taken from 2,188 patients who were treated at 26 Alzheimer's diseases centers.
According to the National Institutes of Health, the patients took a battery of clinical and behavioral tests, and after their deaths their brains were examined.
Researchers found that 93 percent of those in the study had been properly diagnosed as having Alzheimer's while still alive. But 45 percent who were found to have other forms of dementia had also been diagnosed as having Alzheimer's.
Such false-positive diagnoses dropped from 45 percent to 16 percent, however, when the Apo E gene test was applied, thus proving the usefulness of the test.
Because 97 percent of those in the study were Caucasians and receiving specific treatment, the researchers say the study does not apply to other ethnic groups or to those whose health care differs from those in the study.
Correspondent Jed Duvall contributed to this report.