The Corpus Callosum

GrrlScientist wrote a post last month about a potential genetic test for bipolar disorder.  Read that first to get some background.

Now, it turns out that a company is selling a testing kit that you can use yourself, in the privacy of your own home, to see if you have genes that increase the risk of bipolar disorder.

At-Home Psychiatric Gene Tests Stir Debate
New Methods Of Testing Patients' Risk May Lead To More Questions Than Answers
SAN DIEGO, March 23, 2008

(AP) Dr. John Kelsoe has spent his career trying to identify the biological roots of bipolar disorder. In December, he announced he had discovered several gene mutations closely tied to the disease, also known as manic depression.

Then Kelsoe, a prominent psychiatric geneticist at the University of California, San Diego, did something provocative for the buttoned-down world of academic medical research: He began selling bipolar genetic tests straight to the public over the Internet last month for $399.

Dr. Kelsoe is a respected physician.  He's a professor of psychiatry at UCSD.  He started a company, Psynomics, that already has two tests on the market.  From their site:

Psynome™ – tests for two mutations of the GRK3 gene that are associated with bipolar disorder.

Psynome2™ –tests for gene mutations in the Promoter L allele gene that predicts patient response to serotonin-based drugs, the most commonly prescribed drug therapies in psychiatry today. These tests are useful to your doctor in making a timely and accurate diagnosis of your condition and prescribing the right medication.  The tests can be ordered individually or combined.

GrrlScientist's post makes note of some of the serious concerns regarding this kind of testing.  The news article about Psynomic's tests underlines some additional concerns.  From the AP article:

The proliferation of these tests troubles many public health officials, medical ethicists and doctors. The tests receive almost no government oversight, even though many of them are being sold as tools for making serious medical decisions.

Health experts worry that many of these products are built on thin data and are preying on individuals' deepest anxieties.

"People are always rushing to the market on the basis of one or two studies," said Dr. Muin Khoury, director of the National Office of Public Health Genomics at the Centers for Disease Control and Prevention. "We have very little evidence that telling people their genetic information is going to make any difference."

That last point is the key to this matter.  In order to know if the test is worth anything, you would have to do some kind of study that shows that the people who get the test, do better in the long run.  

It is one thing to be able to tell whether the mutations are present.  In is another thing to show that the knowledge makes a difference in the outcome of the treatment.

What if you have all the symptoms, along with a characteristic history, but the test is negative.  Are you going to withhold treatment?  That would be a terribly risky thing to do.  What if you have no symptoms, but the test is positive?  Are you going to go ahead and take medicine for the rest of your life?  Probably not.  At least, not without some solid data to show that asymptomatic people who undergo treatment, in such a circumstance, do better in the long run.

Now, I realize that I've presented this as though it always were a clear dichotomy.  It is not.  The middle ground gets very murky, and we would very much like to have a test to steer the way.  

Ordinarily, we would want to have several valid, replicated studies that use the test and show that it improves outcomes.  

I want to believe that a test like this will work.  In fact, I do believe that we eventually will have one.  Perhaps this is it.  But we have seen things like this before (the dexamethasone suppression test, which I wrote about, incidentally, last week).  Previous efforts have failed to show clinical utility, even if they are useful in a research setting.  Any proposed test will have to meet a high standard before it will make any sense to put it into use.  Even then, it is doubtful that it would make sense for a person to do it at home.