This idea is so bad that I might even agree with a Scientologist about it (OK, not really). A company I will not name or link to has developed a home genetic test for bipolar disorder. What could be so horrible about making it easier for people to diagnose diseases?
Well, first there is a problem of “begging the question”: does the test do what it is purported to do?
(Test X)â¢ – tests for two mutations in the GRK3 gene that are associated with bipolar disorder. Patients who have either of these two mutations, are Caucasian, of Northern European ancestry and have a family history of bipolar disorder, are three times more likely to have bipolar disorder.
Three times more likely than whom?
And what does “3x more likely” mean? That is a statement of risk, but without knowing the baseline risk, it’s hard to know what to think. Using prevalence data from the NMH , there are about 5 million people in the U.S. with bipolar disorder. That’s about 1 in 60 people. “Three times more likely” might mean your chances go up to 3 in 60 (from 1.7% to 5%, correct ethnicity only, please). But it probably doesn’t mean that at all. The only way to really know what it means is to get a hold of the test characteristics, which I can’t seem to find. Accuracy of diagnostic tests depends on many different factors including how common the disease is in a population. It is unlikely that patients and doctors will know how to interpret a positive or negative result—I know I won’t be able to.
Then there is the problem with defining “bipolar disorder”. Bipolar Spectrum? Bipolar I? Bipolar II? What about the patient’s experience? Most mental illnesses are defined by patient experience since the underlying etiologies are not known. Neither are mental illnesses homogeneous disorders. Each diagnosis might actually encompass many different “diseases”.
Does this test add anything to our current diagnostic paradigm? I can’t see how. Once again, for an illness of unknown etiology, based on description of behavior and thought, a genetic test is not useful.
And I won’t even touch the ethical issues of medical genomics.
Empowering patients, whatever that means, is a good thing. But giving them “noise” in the guise of information isn’t helpful. This is not much different than the CT scanners that were doing huge business a few years ago, promising a great look at your insides. It provided that, but without any context for interpretation. For a new diagnostic test to “go live”, it must have data to back up it’s utility. It’s not enough that it accurately measure a particular parameter—that parameter must have meaning.
Genetic testing will probably gain in importance in all fields of medicine, including psychiatry. But selling unproven tests is bad medicine.