DNA testing "can provide information for diagnosing, treating and preventing illness," according to the Mayo Clinic. Screenings can help find genetic disorders before the symptoms of the disorder occur, in adults and fetuses. A blood sample is taken and the DNA is analyzed to find alterations to the person's gene. For example, if the symptoms of a genetic disorder begin in a person's 40s, DNA testing may be done in the person's 20s or 30s. According to the Human Genome Project Information website, there are over 1,000 DNA tests available. However, as the Mayo Clinic points out, DNA testing does have its limitations.
Diagnostic Testing
Diagnostic testing is done if you suspect that you have a genetic disorder. Examples of disorders that can be detected include adult polycystic kidney disease, hemochromatosis and Charcot-Marie-Tooth disease. Your doctor will take a blood sample and send it to a laboratory for testing. The laboratory will use the blood sample to map out the patient's DNA and determine if there are any abnormal genes that are associated with the disease.
Presymptomatic Testing
Presymptomatic testing is done if you have a family history of a genetic condition. Testing is performed before any symptoms appear. The purpose of presymptomatic testing is to see if you are at risk, and if treatment options are possible. Examples of genetic disorders that can be diagnosed through presymptomatic testing include Alzheimer's disease and hereditary nonpolyposis colon cancer, according to the Human Genome Project Information website.
Carrier Testing
Carrier testing is another form of presymptomatic testing; however, carrier testing focuses on whether parents carry a copy of an abnormal gene that can be passed on to their children. Blood samples are taken from both parents, and the DNA is analyzed for the presence of the abnormal gene. Carrier testing is recommended for couples who have a genetic condition in their family, such as sickle cell anemia or cystic fibrosis.
Prenatal Testing
Prenatal testing is a form of DNA testing that is done while the fetus is in utero. The doctor can use amniotic fluid or a sample of the placenta. Prenatal testing is done to detect disorders like spina bifida and Down syndrome. To detect Down syndrome, the chromosomes are mapped out to determine an extra chromosome. Spina bifida is determined by using protein markers in the amniotic fluid.
Newborn Screening
Some states, according to the Mayo Clinic, require that newborn children undergo DNA testing for specific disorders, such as congenital hypothyroidism and phenylketonuria. The purpose of these newborn screenings is to detect these disorders early and provide treatment.
Results
Results can be difficult to interpret, according to the Mayo Clinic. If the test comes back positive, then the specific genetic alteration has been detected. However, as the Mayo Clinic points out, detection of the breast cancer gene, BRCA1 or BRCA2, does not indicate that you have breast cancer, only that you are at high risk. For negative results, the genetic alteration may not be detected, but accuracy can vary. According to the Mayo Clinic, "everyone has variations in the way genes appear (polymorphism) and, often, these variations (do not) affect your health. But sometimes it can be difficult to distinguish between a disease-causing gene alteration and a harmless gene variation." If the test results come back inconclusive, the Mayo Clinic recommends further testing.
