Presymptomatic testing (that is, testing a healthy person before symptoms appear) may be considered for a genetic disorder for which there is a family history. The decision to undergo this type of testing is not usually straightforward and should always be accompanied by genetic counseling. There are a number of considerations to take into account when deciding whether to proceed with testing. The first is the usefulness of the information. How will knowing the genetic information benefit the person? Testing is more favorable when preventive treatment is available, when results might have a significant impact upon life decisions, such as having children or getting married, or if it will ease extreme anxiety to learn one's genetic status. If no treatment is available, as in the case of Huntington's disease and other triplet repeat diseases, the information may be of less benefit. In some cases it may even be psychologically harmful.
The second consideration is accuracy, not only of the actual test result, but also of its ability to predict the development of the disorder. Some disorders are caused by more than one gene, or by multiple changes or mutations in the same gene. A given test might not be able to look at all mutations or every gene that causes a disorder, leaving a person who tests negative with doubt as to whether they are truly mutation-free. Some genetic tests, particularly those for complex disorders, are for susceptibility genes. As the name implies, these are genes that make a person susceptible to developing a disorder, but do not guarantee it. An example of this is breast cancer. When deciding whether or not to test for such a disorder, it is important to ask how it would feel to test positive for a susceptibility gene for a serious genetic disorder that may never develop.
The third consideration is risk of personal harm. Testing positive for a disorder may put a person at risk of economic or social harm. Although rare, there have been instances where individuals have been denied insurance, employment, or both based on the results of genetic testing. Also, a person may be at risk of experiencing psychological or emotional problems after undergoing genetic testing. There have been instances, particularly with Huntington's disease testing, where individuals have committed suicide following a positive test result. All of these factors must be presented to, discussed with, and weighed by the individual considering testing, in the context of genetic counseling and prior to making a decision about testing.
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Medicine EncyclopediaGenetics in Medicine - Part 2Genetic Testing - Prenatal Genetic Testing, Assisted Reproduction, Newborn Screening, Symptomatic Genetic Testing, Carrier Testing, Presymptomatic Testing