What is Genetic Testing?

Genetic tests use a variety of laboratory techniques to determine if a person has a genetic condition or disease or is likely to get the disease. Individuals may wish to be tested if:

There is a family history of one specific disease.
They show symptoms of a genetic disorder,
They are concerned about passing on a genetic problem to their children.

Genetic tests include techniques to examine genes or markers near the genes. Direct testing for diseases such as cystic fibrosis and sickle cell anemia come from an analysis of an individual's specific genes. A technique called linkage analysis, or indirect testing, is used when the gene cannot be directly identified but can be located within a specific region of a chromosome. This testing requires additional DNA from an affected family member for comparison. Because each person's DNA is unique (except for identical twins), genetic tests also can be used for individual identification ("DNA fingerprinting").

Genetic testing is a complex process, and the results depend both on reliable laboratory procedures and accurate interpretation of results. Tests also vary in sensitivity , that is, their ability to detect mutations or to detect all patients who have or will get the disease. Interpretation of test results is often complex even for trained physicians and other health care specialists. When interpreting the results of any genetic test, one must take into account the probability of false positive or false negative test results. Special training is required to be able to analyze and convey information about genetic testing to affected individuals and their families.

Types of Genetic Testing

Carrier Identification includes genetic tests used by couples whose families have a history of recessive genetic disorders and who are considering having children. Three common tests include those for cystic fibrosis, Tay-Sachs disease, and sickle-cell trait.

Prenatal Diagnosis is genetic testing of a fetus. This may occur when there is a risk of bearing a child with genes associated with mental retardation or physical deterioration. Down Syndrome is one of the most common genetic diseases screened by this method.

Newborn Screening is frequently done as a preventative health measure. Tests usually have clear benefit to the newborn because treatment is available. Phenylketonuria and congenital hypothyroidism are conditions for which testing is conducted in all 50 states.

Late-onset Disorders include adult diseases such as cancer and heart disease. These diseases are complex and have both genetic and environmental causes. Genetic tests may indicate a susceptibility or predisposition for these diseases. There are diseases caused by single genes, such as Huntington's disease, that also are seen later in life and can be tested at any time.

Identification of genetic information belonging to a specific individual has received a great deal of press coverage lately. Profiles (aka "DNA fingerprints") are complied from the results of DNA testing for one or more genetic markers to identify unique characteristics of an individual. This information is currently used in legal cases involving paternity and in criminal investigations, and it can be used in time of major accidents, disasters, or wars to identify those who have died.

Ethical, Legal, and Social Issues in Genetic Testing

Information from genetic testing can affect the lives of individuals and their families. In addition to personal and family issues, genetic disease or susceptibility may have implications for employment and insurance. Therefore, careful consideration in the handling of this information is very important. Critical issues include:

Privacy - the rights of individuals to maintain privacy. Some genetic tests are required or strongly encouraged for developing fetuses and newborn babies. If an infant is found to be a carrier or likely to develop or be affected by an inherited disease, these findings may affect the future employability or insurability of the individual.
Informed consent - obtaining permission to do genetic testing. One must have knowledge of the risks, benefits, effectiveness, and alternatives to testing in order to understand the implications of genetic testing.
Confidentiality - acknowledgment that genetic information is sensitive and access should to limited to those authorized to receive it. Future access to a person's genetic information also should be limited.

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