Consumer Gene Tests: Help or Harm?
Experts, Test Makers Battle Over Selling Genetic Tests to Patients
Genetic Tests for Antidepressant Sensitivity continued...
Genelex offers not only to test for enzymes that affect SSRI processing, but
also to interpret the test results. Although the web site clearly states that
these interpretations are intended as an aid to patients' doctors, the results
are provided directly to the patient who pays for them.
The Genelex site makes specific claims about the types of information
genetic testing CYP will provide -- such as proper dosage and drug interactions.
Yet a January 2007 review of CYP tests for SSRI sensitivity -- by the CDC's
EGAPP (Evaluation of Genomic Applications in Practice and Prevention) working
group -- found the test wasn't ready for prime time. Alfred O. Berg, MD, MPH,
professor and chairman of the family medicine at the University of Washington,
chairs the EGAPP working group.
"We don't say the test can't be helpful. We just say you can't tell, and
until you can tell, don't use it," Berg tells WebMD. "We are not saying
the manufacturers are making false claims. ... We were a little disappointed
that the evidence wasn't stronger than it was."
Coleman says the EGAPP standard is too high.
"That is the very most rigorous, very most conservative standard of
proof," he says. "It is certainly appropriate for new drugs, but not
for new genetic tests. These demands for clinical trials are over the top in
terms of the level of proof we need to use this testing. There is an asymmetry
between the level of benefit [from genetic testing] and this level of
Berg says EGAPP is skeptical of this "genetic exceptionalism"
suggesting that genetic tests are somehow different than other medical
"One of the things these companies don't emphasize is that you can
develop a plausible argument for how these genetic tests might work, but we are
also interested in the harmful effects," he says. "With all tests,
there are potential benefits and potential harms. We did not find evidence for
either one of those in CYP tests for SSRI sensitivity."
How Should Genetic Tests Be Used?
Javitt and colleagues worry that patients armed with genetic test results
will stop taking their medicines or change their doses without first consulting