Definition Genetic screening is the process of looking for indications of a genetic disease. A genetic disease is a condition that is passed down from a parent to his or her offspring. Genetic screening is usually done before any signs of disease are present. The procedure is undertaken for several reasons. It may be done to determine if someone will develop a genetic disease. Examples of common genetic disorders are:
Genetic screening is sometimes done to determine if a person can pass on a genetic disease, even if he or she is not at risk for developing the actual condition. It also may be done as part of a study of the whole population.
Who is a candidate for the test? Some genetic screening, such as phenylketonuria or PKU testing, thyroid disease or cystic fibrosis is done on all newborn babies in this country. It is done to detect some genetic diseases that can be prevented if they are identified early in the child's life. People who have relatives with genetic disease may seek genetic screening to determine if they are at risk for developing the condition as well. They also might want to know whether they can pass it on to their children.
How is the test performed? Genetic screening is not always a sophisticated test. It may involve looking for certain chemicals in blood or urine. It also may involve DNA testing or chromosome analysis. Usually, a sample of blood or urine is collected and sent to a laboratory for analysis. Simple tests are done in many laboratories around the country. Population screening is often done in state run laboratories. Sophisticated DNA tests and chromosome analysis are done in genetics laboratories.
What is involved in preparation for the test? Screening for some compounds in the blood or urine may require fasting or a special diet before the test. DNA tests and chromosome analysis do not require preparation. A person should consult the doctor for specific instructions.
What do the test results mean? If certain compounds are found in the blood or urine, the screening test is said to be positive. This means that there is reason to believe that a genetic disease is present. There are many false positives. Therefore, a more refined test is done on all positive cases. If the refined test is positive, the genetic disease is present and treatment is started. DNA tests are accurate. If the results are positive, the potential for the disease is present and action is taken. Genetic counselling may be appropriate. chromosome analysis is also accurate. If the results are positive, there is a risk to pass on a genetic disease and action is taken.
Author: Ronald J. Jorgenson, DDS, PhD, FACMG Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
