Genetic tests are done either to diagnose genetic disorders or identify risks associated with developing a disease. Testing problems range from the accuracy of the genetic tests and oversight of the testing labs, to the growing market for mail-order genetic testing, to ethical concerns about testing for conditions that may or may not lead to disease.
Background
According to the Centers for Disease Control and Prevention, or CDC, the number of clinical genetic tests available more than tripled from 423 in 2000 to approximately 1,300 in 2008. However, this growth in the availability of testing has not been matched with oversight of the marketing of the tests, regulation of testing laboratories or medical interventions to prevent or ameliorate the diseases or risks identified.
Genetic Testing
All genetic testing is done to identify genetic defects tied either to a specific disease or an increased risk of disease. This distinction between diagnosing a specific disease and identifying an increased risk is important. Also important is whether the genetic information has medical significance.
Diagnostic Testing
A test that diagnoses a specific disease for which an intervention is available is PKU, a metabolic disease for which newborns are routinely tested. Untreated, PKU leads to mental retardation. Fortunately, a specialized diet can largely mitigate the metabolic defect.
In contrast, the genetic defect of Huntington's disease, a debilitating and fatal disease of older adults, can be accurately diagnosed, but there is no intervention to delay or treat the disease. Those at risk may not want to know their genetic status.
Testing for Risk Factors
Most genetic tests only identify a higher risk of developing an illness, such as Alzheimer's or breast cancer. Here, the genetic defect may be only one of many factors contributing to the disease. At issue in risk testing is whether, other than for research purposes, there is any medical rationale for testing. For Alzheimer's, there is no known intervention that will more than moderately slow memory loss. Women having BRCA1 or BRCA2 genes have a high risk of getting breast cancer. In this case, some have taken the aggressive step of having mastectomies to reduce the risk.
Laboratory Issues
With the rapid growth of genetic testing has come many reported problems, including the inadequate specifications of testing conditions, inadequate personnel training and qualifications, inadequate quality assurance practices and misunderstanding or misinterpreting test results. In 2009, the CDC issued guidelines for genetic testing laboratories.
Mail-Order Genetic Tests
According to a 2009 Government Accountability Office, or GAO, report, direct-to-consumer tests, those available through the mail, have significant problems. First, none has undergone Food and Drug Administration pre-market review. Second, the GAO found samples from the same individuals sent to different labs produced widely variable results. One individual who sent samples to three different labs was told he had below average, average and above average risk of developing prostate cancer. Third, the information provided to consumers is complex, with limited explanation, and often is not medically actionable.
Other Issues
The quality and availability of genetic counseling is often raised as a problem.
Additionally, patient privacy of genetic information, particularly related to insurance company exclusions for pre-existing conditions, is a concern.
References
- Government Accountability Office: Direct-To-Consumer Genetic Tests: Misleading Test Results Are Further Complicated by Deceptive Marketing and Other Questionable Practices
- Centers for Disease Control and Prevention: Good Laboratory Practices for Molecular Genetic Testing for Heritable Diseases and Conditions
- National Institutes of Health: MedlinePlus: Genetic Testing
