Genetic testing holds great potential for the future of medical care. It offers many benefits, including the provision of important information that can be used when making decisions about having a family and taking care of one’s own health. However, there are also limitations. For this reason, it is important to understand the nature of genetic testing and the information that it can and can’t provide. For example:
Clinical genetic tests are not just descriptive as many laboratory tests are (such as describing the glucose level in your blood), but may be predictive as well. Predictive tests may not give a yes/no answer, but instead will tell what the chances are of developing a particular genetic condition. Such results may not be definitive and may leave a person wondering what to do with those results, particularly if available treatments or therapies are limited. However, the profession of Genetic Counselling exists to provide individuals and their families with accurate information and help interpret genetic results so that individuals and their families can make their own decisions.
Many genetic tests will only look for the presence or absence of a specific genetic mutation; the test cannot always guarantee that the disease will develop nor can the test provide information about other genetic diseases not being specifically looked for by that test.
While the test may detect a particular problem gene, it cannot predict how severely the person carrying that gene will be affected. Again with cystic fibrosis, symptoms may be mild bronchial abnormalities or may extend to severe lung, pancreatic and intestinal problems.
Many genetic tests cannot detect all of the variations that can cause a particular disease. For instance, with genetic testing for cystic fibrosis, most genetic testing panels only look for the more common mutations and further specialised testing may be needed to identify rare causes of this disease. Similarly, some diseases are caused by mutations in more than one gene and financial constraints may limit the degree to which multiple genes can be analysed using current techniques.
Some diseases are the result of an interaction between one’s genes and one’s environment. The way in which these interactions cause disease is not clearly understood. Examples of these diseases include coronary heart disease, type 2 diabetes, obesity and Alzheimer disease.
Legal issues, such as patient privacy, use of genetic testing to determine insurance coverage and the use of archived patient samples are some of the broader social issues to be considered.
Because of these limitations, genetic test results can be a mixed blessing. An absolutely essential component of clinical genetics testing is giving your informed consent to do the tests and knowing what you want to do with the results of these tests. Knowing your legal rights and making certain that your privacy is respected may also be useful. Educating yourself about genetic tests and talking to your medical provider, and/or genetic counselling service, may help you decide whether you think you should have genetic testing performed.
It is important to remember that genetic testing is different from other types of laboratory testing in the sense that the results may have implications, not only for you the patient, but also for family members who may need to be tested as well. Genetic education and counselling is therefore often advised to help understand and cope with the results of genetic tests.