July 15, 2009 -- If your parent has Alzheimer's disease, should you get tested for a gene that puts you at high risk of late-onset Alzheimer's?
Most doctors say no. They worry that you wouldn't understand what it means to carry the ApoE-e4 gene. And they worry you'll freak out and become clinically anxious or depressed.
Those doctors have been wrong on both counts, suggests a new study by Robert C. Green, MD, MPH, co-director of the Boston University Alzheimer's disease program at Boston University, and colleagues.
"We have demonstrated that the assumption that it would be common to have psychological problems is not so," Green tells WebMD. "And people do in fact understand the concept of a risk gene. They do not automatically move to the assumption that if they have the gene they will get Alzheimer's."
Understanding the results of an Alzheimer's gene test is tricky. People who inherit a single copy of the gene are at increased risk of getting Alzheimer's disease as they age. People who inherit two copies of the gene are at very high risk of the disease -- even though it's not a sure thing. And even if you don't have the gene, you can still get Alzheimer's disease.
Alzheimer's Gene Test Not Recommended
There are a lot of good reasons not to get tested, says Ronald C. Petersen, MD, PhD. Petersen chairs the Alzheimer's Association medical and scientific advisory council. He's also director of the Mayo Alzheimer's Disease Research Center in Rochester, Minn.
"Most physicians have taken the position that ApoE testing is not recommended for asymptomatic people," Petersen tells WebMD. "Part of the rationale is we can't do anything about it. And this becomes part of your medical record and discoverable by insurance carriers. And how will people deal with this psychologically? That is where the Green study comes into play."
Green and Alzheimer's researchers from a number of centers in the U.S. and Canada recruited 162 50-something, mentally healthy adults with a parent who had Alzheimer's disease. None of the study participants had any sign of Alzheimer's disease. All were willing to get an ApoE test, even though they knew that they might not learn the results.
The researchers disclosed the results of the test to two-thirds of the participants. Before and after the ApoE test, participants received extensive genetic counseling. All study participants then underwent a battery of psychological tests over the course of the next year.
- Those who learned their test result -- even if it was bad news -- suffered no more anxiety or depression than those who did not learn the result.
- Six weeks after learning the result of the test, those who learned they had the Alzheimer's gene suffered a bit more distress -- but they got over it.
- As might be expected, those who learned they did not carry the gene had feelings of relief.
Ongoing studies will look at whether testing had any bad long-term effects.
Pros and Cons of Alzheimer's Gene Test
"There is still a lot to explore in this," Green says. "The bottom line is in conventional medical centers, ApoE is still an experimental test. We are not advocating using it clinically, and we will not use clinically at the present time."
But that doesn't mean people shouldn't get the test -- as long as they understand what they are doing, says Jeffery M. Vance, MD, PhD, director of the Center for Genomic Medicine at the University of Miami Institute for Human Genetics.
"It does not surprise me that with proper medical consultation, patients took the information in an appropriate fashion," Vance tells WebMD. "As a doctor, you provide them the pros and cons -- and that includes all the legal concerns, the medical concerns, and their concerns about the impact of the test on others in their family, their kids. Then let them make the decision."
Perhaps the biggest argument against ApoE testing is that there's no treatment to prevent or delay Alzheimer's disease. That may soon change.
"In Alzheimer's disease, we are talking about a disease where treatments are expected in the near future," Green says. "Once there are treatments, the next clinical question is whether they delay Alzheimer's onset in at-risk people. At that point, it will be important to know who is at higher risk."