DTC genetic testing: What do you tell patients?

October 1, 2009

Patients are going to have direct-to-consumer genetic tests done, regardless of our position on the subject. At the very least, we can offer them sound advice on the matter.

Once upon a time, medical advertising was considered quite inappropriate. In fact, physicians over a certain age may recall when directly communicating with the general public was limited to the Yellow Pages or perhaps understated announcements concerning retirements or new partners. This thinking now seems terribly antiquated, so last century. One is almost expected to advertise, and with great elan. Some may wistfully recall simpler times, but that was before we had the internet.

And it's not just physicians who are advertising. Hospitals and pharmaceutical companies likewise peddle their wares to the public with great flare. Advertisements behind home plate remind us where sports injuries can be treated; time outs and injury updates during football games are sponsored by health systems. Clever television ads encourage backyard quarterbacks to benefit from sildenafil. It would be quixotic for us to resist this trend. The train has long since left the station.

The latest direct-to-consumer (DTC) barrage, however, seems a bit more pernicious. The situation started with burgeoning genetic discoveries which, coupled with meteoric increases in technology, have permitted us to determine the risk of developing many disorders or suffering drug reactions. Testing for two variants in the cytochrome P-450 2C9 gene (CYP2C9) and one in the vitamin K epoxide complex 1 gene (VKORC1), for instance, can identify 50% of individuals who will experience hypersensitivity or resistance to warfarin.1,2 Similarly abacavir is a highly effective drug for managing human immunodeficiency virus (HIV) – infected patients, but 5% to 8% experience potentially fatal hypersensitivity. This can be accurately predicted on the basis of allele HLA-B*5701, the presence of which contraindicates abacavir therapy.3

There seems to be a market for these DTC kits. One company offers a profile for prostate cancer, touting its ability to predict up to a 5-fold increased risk, or 9-fold if family history is taken into account. Another kit offers to assess one's nutritional needs. Even the sequence of the entire genome, or selected genes, can be ordered, a process approved by regulatory authorities in California.

Given this onslaught of information, it is inevitable that at least some of our patients will be interested. Yet, they may not appreciate certain unintended consequences. An "adverse" genetic profile does not confer certainty of disease, nor the converse. What role then, should we obstetrician-gynecologists play in DTC testing?

First, accept that patients will have DTC performed with or without our approval, and often inappropriately. Low risk patients are indeed influenced by media ads.4 Thus, we will be presented with test results post hoc, asked to explain their meaning, and recommend often unavailable preventative measures.

Second, encourage patients to tell us of their interest in a given DTC test in advance, rather than merely waiting to present us with results. Does the patient truly understand that a DTC test may not provide a definitive answer, but only a relative risk? Or, that even a 20-fold increase in relative risk may confer a very low absolute risk? Or, that there are no treatment options at this time? Such discussion may result in ardor for a given test diminishing. Young women often ask for amniocentesis in order to have a "genetically perfect child". When they learn such a request is unrealistic, interest wanes.

Third, the obstetrician-gynecologist needs to determine the extent to which he or she is comfortable in interpreting a given DTC result. If the disorder in question is outside our discipline, we could demur. Not so for DTC results concerning conditions like ovarian cancer. The American College of Medical Genetics offers useful minimal requirements for providers assessing direct-to-consumer (DTC) tests.5 They stipulate: