What information can genetic testing provide?
Genetic testing can be predictive, discovering whether an individual has an inherited disposition to a certain disease, before symptoms appear. Genetic tests can also confirm a diagnosis if symptoms are present. Tests can determine whether a person is a carrier for the disease. Carriers won't get the disease, but can pass on the faulty gene to their children. Prenatal testing can help expectant parents know whether their unborn child will have a genetic disease or disorder. Newborn screening tests infants for abnormal or missing gene products.
Individuals in families at high risk for a disease live with troubling uncertainties about their own future as well as their children. A negative test - especially one that is strongly predictive - can provide an enormous sense of relief. A positive test can also produce benefits. In the best circumstances, a positive test enables the person to take steps to reduce risk. These steps could include regular screening for the disease or lifestyle changes, such as a change in diet or regular exercise. A positive test can relieve uncertainty, and can enable people to make informed decisions about their future.
Reasons for Genetic Testing
Predictive testing identifies people who are at risk of getting a disease before any symptoms appear. Predictive tests include those that screen for some inherited predispositions to certain forms of cancer, such as colon and breast cancer. Being predisposed does not mean that the individual will get the disease. It means the person has a certain risk of developing the disease.
Carrier testing can tell individuals if they are carriers of an inherited disorder that they may pass on to their children. A person who has only one abnormal copy of a gene for a recessive condition is known as a carrier. Carriers won't get the disease, but can pass on the defective gene to their children. Cystic fibrosis and Tay-Sachs disease are examples of disorders for which parents can be carriers.
Prenatal testing is available to people at risk for having children with a chromosomal abnormality or an inherited genetic condition. Two procedures are commonly used in prenatal testing. Amniocentesis involves analyzing a sample of amniotic fluid from the womb. CVS (chorionic villus sampling) involves taking a tiny tissue sample from outside the sac where the fetus develops. Prenatal testing is often used to look for disorders such as Down syndrome, spina bifida, cystic fibrosis, and Tay-Sachs disease.
Newborn screening, the most widespread type of genetic testing, tests infant blood samples for abnormal or missing gene products. For example, infants are commonly screened for Phenylketonuria (PKU), an enzyme deficiency that can lead to severe mental retardation if untreated.