Our test can tell you.” If direct-to-consumer drug ads are a pain in your practice, just wait for direct-to-consumer gene testing. Patients are already arriving at the doctor’s office with a baker’s dozen questions. My sister has this disease. Am I going to get it? Is there a genetic test for it? What should I do if I test positive? When can I have this bad gene snipped out and replaced with a good gene so I don’t get it? In an AMA survey, 71% of adults questioned said they would ask their PCPs about genetic links to disease. Yet studies show most physicians do not know enough about the benefits, costs, and limitations of genetic testing to answer patients’ questions.

  Raw data from the human genome project are being turned into clinical diagnostic tools, so doctors must start “thinking genetically,” says John Wilkinson, MD, a Mayo Clinic FP who advises colleagues about how gene testing will affect their practices. “Genomics will transform what doctors do, from diagnosing and treating to predicting and preventing,” he says. “It’s not too farfetched to say that genomics will affect every doctor’s practice for every patient.” But we’re not there yet. Medicine’s crystal ball is still taking shape.

  “What we have,” says Dr. Wilkinson, “is a warehouse full of phone books in a foreign language that uses four letters. You can sequence a patient’s entire genetic profile, but no one can tell you what it means.” Media hype, combined with a natural desire to know, prompts patients to ask about-or demand-genetic testing. For now, physicians must help patients separate hope from hype. About 900 genetic tests have been developed. Physicians can order some 450 of them. Most test for rare disorders. A few test for single-gene dominant mutations like Huntington’s disease. If you’ve got the gene, you’ll get it.

  But most tests are not so black and white. Instead, they predict risk-a patient may or may not develop the condition. It’s these predictive tests for adult-onset conditions like cancer, heart disease, and Alzheimer’s that are hardest to discuss with patients. Most tests are not yet part of the standard of care for asymptomatic patients, notes Dr. Wilkinson. “There are plenty of tests that are two mouse-clicks away for my patients,” he says, “but it’s unlikely they’ll do most of them any good.”

  Breast-cancer testing is among the most hype-infected, according to Roberta Pagon, MD, a medical geneticist at the University of Washington-Seattle who helped create the GeneTests-GeneClinics website (www.genetests.org), where physicians can look up what tests are available and who does them. “Most women who will get breast cancer don’t have a mutation in the genes BRCA1 or BRCA2,” says Dr. Pagon. “Only women from high-risk families should be tested for mutations in these genes.”

  If a patient tests negative, she still has the general population’s one-in-nine chance of developing breast cancer. If she tests positive, her lifetime risk could be as high as 85%. But then what? It’s not clear whether breast self-exam, mammography, or even prophylactic mastectomy can help these patients, according to Dr. Pagon. “At this time, BRCA1/2 testing is really a poor model for using genetic testing to reduce morbidity and mortality from an inherited disease.” With the present technology, testing every patient who wants to be tested is costly, inefficient, and falsely reassuring. So when should it be offered?

  Ideally, when a patient has a strong family history for a particular condition and when early diagnosis could lead to treatment that can lower morbidity and mortality. Even for untreatable conditions, testing can help patients plan their lives. Most physicians don’t realize they can’t simply order a test for an at-risk patient, says Dr. Pagon. “You have to first test the patient’s relative who has the condition. Many mutations can cause the same disorder. You have to determine what mutation the patient is at risk for.” In families for which linkage testing is used, several family members must be tested in order to get meaningful results.

  DNA tests usually use white blood cells, although some labs prefer cheek swabs. There is no all-in-one test that checks for every inherited disorder. Most are tailored to specific diseases, and cost anywhere from $100 to $3,000. Many insurance policies still do not pay for them, even when family history is present. A few tests are available directly to patients through private labs, but most require a referral. Many labs won’t test without proof of patient counseling and informed consent.

  Does the patient understand the limitations of the test? What do they plan to do with the results? Will they inform other family members at risk? Patients need to understand that most genetic testing does not offer a yes-or-no answer. Except for a few rare conditions like Huntington’s, most conditions are caused by a complex interplay of several genes, life-style, and environment.

  When a patient tests positive, often nothing medical can be done to rectify it. But that’s not necessarily a reason to say no to testing, says Dr. Pagon. “I had three families this week thank me for telling them the source of their child’s untreatable condition,” she says. “Patients want to know what causes it. They want to talk to others about living with the condition. Many patients want information and coping strategies as much as test results.”—Howard Bell

back to top