Alzheimer's Test That's 100 Percent Accurate? Not Yet

Doctors say the test, while a step forward in screening, is no 'breakthrough.'

ByABC News
August 10, 2010, 10:12 AM

Aug. 10, 2010— -- Researchers claimed to have identified markers for early Alzheimer's disease in some patients by analyzing results of a spinal tap, according to an article published Monday in the Archives of Neurology. Their results, they claim, are nearly 100 percent accurate in predicting Alzheimer's in some patients.

But many experts are quick to question how reliable these results may be.

"The test is an advance and has tremendous research potential. This is sure," said Karl Herrup, chair of Cell Biology and Neuroscience at Rutgers University in Piscataway, N.J.

But, he added, "a dangerous, though unintended, consequence of the '100 percent accuracy' descriptor is that people who may not be on the fast track to Alzheimer's will end up frightened unnecessarily from a positive test result."

Click Here for a Checklist of 10 Alzheimer's Warning Signs

"[T]he fear of [Alzheimer's disease] is so strong in our population that feeding it any way seems not in our best overall interest."

And ABC News Senior Health and Medical Editor Dr. Richard Besser said the test is not yet ready for prime time.

"This test isn't ready to be used on healthy, normal people," Besser said on "Good Morning America."

"It will be useful for research, doing drug trials in a group of people who may be at high likelihood to go on for Alzheimer's disease."

The researchers measured tracked results from a spinal tap from three groups of patients: those with Alzheimer's, those who had been diagnosed with mild cognitive impairment (MCI), and those who were relatively healthy. Specifically, the researchers looked for patterns in the levels of two types of proteins, known as tau and amyloid, that appear to have a link to the chances of developing Alzheimer's. The data suggested that patients who had Alzheimer's or MCI had a combination of low levels of amyloid beta protein, known to form plaques in the brain, and high tau protein levels, which is known to build up dead nerve cells in the brain.

However, one-third of the study participants were identified as having levels of these proteins that suggested an Alzheimer's diagnosis -- even though they were cognitively normal. Herrup said that even if the test results are accurate, it may only mean that a patient could have a marker for the disease, but may never get the disease. He said for the moment, there is nothing a patient can do once they learn about the results of the test.

"People who take this test and are told the results are going to need a very high degree of medical sophistication in order to think about their results properly," Herrup said.