Due to recent discoveries of new genes and the development of new testing methodologies, the availability of genetic testing has increased dramatically. Several companies now offer direct-to-consumer genetic testing through which individuals can send in a cheek swab or saliva sample and receive results regarding hundreds of genetic conditions, all without the guidance of a physician or other medical professional. In addition to the positive aspects of genetic testing, there are some definite disadvantages as well.
People who do not receive adequate information or counseling about the limitations of genetic testing may falsely assume that a negative test result eliminates their risk for developing a disease. Many genetic tests check for the most common gene mutations responsible for a disease, but do not rule out the possibility of a person developing that disease.
For example, the genetic testing now available for rare hereditary forms of breast and ovarian cancer examines the two main genes responsible for these cancers (called BRCA1 and BRCA2). A woman with a family history of breast or ovarian cancer who tests negative for mutations in BRCA1 or BRCA2 may conclude that she is out of the woods and will not develop one of these cancers. Some women, however, will still be diagnosed with cancer despite a negative genetic test because many cancers are caused by mutations in other genes or by factors not yet understood. Even women who test negative for these hereditary forms of cancer need screening for cancer at the same level of screening recommended for the average woman.
On the other hand, receiving a positive genetic test does not necessarily mean a person will develop a disease. "It's very important that a person knows what type of test she has undergone and what are the limitations of that test," says Melissa Trant, M.S., a genetic counselor. There is a critical distinction between screening and diagnostic tests. A screening test, such as the Expanded AFP blood test that many women undergo during pregnancy, indicates the chance that the baby will have certain conditions, but does not say for sure whether the baby is affected. A diagnostic test, on the other hand, provides definite results and can generally rule a condition in or out. Some people confuse the meaning of a screening test with a diagnostic test and, as a result, can become very anxious if they receive a positive test result. Adequate pre- and post-test counseling about what a test can and cannot reveal, and what the next steps are should a test turn out positive, are imperative for preventing undue anxiety.
Concerns About Discrimination
Despite federal and state laws that protect against possible health care discrimination, many people considering genetic testing are concerned about the chance that their result may adversely affect their insurability. The pace of development of new genetic tests may be ahead of lawmakers' ability to figure out all the protections that need to be in place.
Some people aren't even aware that they or their children are undergoing genetic tests. For example, all states perform newborn screening for various genetic conditions, the purpose being to detect those conditions that would benefit from swift treatment. In most cases, however, mothers are not asked to provide consent for these tests and are not informed of what will happen if a test should return positive. They also aren't likely to know whether their baby's DNA sample will be kept, and by whom, after the testing is complete.
According to Klitzman (J. Genet. Coun., 2010), some individuals who know they are at risk for a genetic condition, such as Huntington's disease, may forgo desired testing because of their fear of genetic discrimination.
- R. Klitzman. Views of Discrimination among Individuals Confronting Genetic Disease. J Genet Couns. 2010 Jan 7.
- Melissa Trant, M.S.; Genzyme Genetics; Los Angeles, CA