So why aren't personal genomic tests ready for primetime?
There are 3 key factors that must be considered in the development and evaluation of genetic tests in clinical practice. First, there is the test's analytic validity, which is the test's ability to accurately and reliably measure the thousands of genetic variants on these tests.
In many cases, personal genomic tests do meet quality standards for laboratories. The second thing we have to look at is the clinical validity of these tests, which is the ability of the test to detect or predict particular diseases and health conditions. This is the area for which the data are in so much flux right now.
Most common diseases, as a matter of fact, like diabetes, cancers, and heart disease, are caused by multiple genes and interactions with environment and behavior. More research is needed to identify the full list of variants and how they influence disease susceptibility.
So far, a simple knowledge of family history for disease seems to be a more important risk factor for most common diseases. Genetic variants associated with diseases that have been identified so far typically account for only a small fraction of the measured impact of family history. Therefore, there is a lot of uncertainty about the risk estimates given by these tests; the estimates could rapidly change and [estimates] also vary by patient characteristics such as age, race and ethnicity, and environmental and lifestyle factors.
Finally, there is the most critical issue of the test's clinical utility, which addresses the question of: if a patient is found to be at increased or decreased risk for a disease, what can be done about it? In this area, there is virtually no information available that looks at the health implications of communicating genomic information and the balance of benefits and harms for using these types of tests.
So what advice should providers offer patients?
First, discuss with patients the limitations of personal genomic tests. These tests are not ready for routine use in clinical practice because of their limited clinical validity and clinical utility. Second, encourage patients to collect and keep an updated family health history. Family health history is a very informative and inexpensive "genomic test" that can be used right now. It reflects genes, behaviors, lifestyles, and environmental factors that are shared among relatives..
Family health history can help healthcare providers assess the presence of many genetic conditions and whether patients and their relatives may have an increased risk for specific diseases
And lastly, use the discussion of personal genomic tests and family history as a teachable moment to encourage patients to improve their health. We can reinforce the value of simple health promotion and disease prevention messages about increased physical activity, avoidance of cigarette smoking, improved diet, as well as adoption of medical screenings to help lower risk for specific common diseases regardless of genes.
The promise of genomics in the practice of medicine is great and exciting, but today the use of personal genomic tests is still not ready for prime time.
Thank you for your attention.
Web Resources
Genetic Testing, CDC Office of Public Health Genomics http://www.cdc.gov/genomics/gtesting/index.htm
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