The idea is that it might be possible to predict which medications might be better for a particular patient. That has appeal, because many people have to try more than one medication in the quest to find one that is both tolerable and effective.
If a person metabolizes a drug much more rapidly than most people, then that person might need a higher than expected dose, or might need to take the medication more frequently than the usual recommendation. If a person metabolizes the drug much more slowly than most people do, then that person might be more susceptible to adverse effects; this might call for a lower dose than what most persons would take.
The test was approved by the FDA. But the approval was based only upon the fact that the test accurately can detect the genes it is claimed to detect. That does not say anything about whether the test has any clinical usefulness.
In fact, there are many things that sound good in theory, but which turn out to have no clinical utility.
The US Centers for Disease Control and Prevention (CDC) set out to determine whether the test has any clinical utility. On 19 December, 2007, they issued a press release on the subject. It was written by Muin J. Khoury, M.D., Ph.D., Director of the National Office of Public Health Genomics (NOPHG).
The resulting study was published in the December issue of Genetics in Medicine (Genet Med. 2007:9(12):819-825) and is openly accessible.
Recommendations from the EGAPP Working Group: testing for cytochrome P450 polymorphisms in adults with nonpsychotic depression treated with selective serotonin reuptake inhibitors
Summary of Recommendation: The EGAPP Working Group found insufficient evidence to support a recommendation for or against use of CYP450 testing in adults beginning SSRI treatment for non-psychotic depression. In the absence of supporting evidence, and with consideration of other contextual issues, EGAPP discourages use of CYP450 testing for patients beginning SSRI treatment until further clinical trials are completed.
Notice that they did not say the test is useless. Rather, they said that there is no evidence that it is useful. We simply do not know. Notice also that they did not say that the evidence is too weak to support a conclusion. There is no evidence at all, at least that they could find.
There is a much longer and more detailed analysis published by the Agency for Healthcare Research and Quality, in this 157-page PDF file. The conclusion is the same. Although we all have high hopes for personalized medicine and pharmacogenomics, this particular test, at this particular time, has no objectively validated utility.
Brain & Behavior
Medicine & Health
Comments
this type of test would actually make the current anti-depressant line more effective than ever.
Posted by: Macnerdzcare | December 23, 2007 10:20 AM