Genetic testing is a type of medical examination that looks for changes, also known as mutations or variants, in DNA. It can be used to confirm or rule out a potential genetic condition, or to determine the chances of a person developing or transmitting a genetic disorder. Currently, more than 77,000 genetic tests are available, and they involve examining DNA, the chemical database that contains instructions on the body's functions. Genetic testing can reveal mutations in genes that can cause a disease or illness.
It can also be used to detect changes in a person's genes that can increase their risk of developing certain medical problems (such as some types of cancer). During pregnancy, genetic testing can be done on the amniotic fluid (through amniocentesis) or on the placenta (using a chorionic villus sample).Genetic testing plays an important role in determining the risk of developing certain diseases, as well as in screening and sometimes in medical treatment. If the genetic test result is positive, it means that the genetic change it was being tested for was detected. When genetic testing doesn't lead to a diagnosis, but a genetic cause is still suspected, some centers offer genome sequencing, a process for analyzing a DNA sample taken from the blood. Although genetic testing can provide important information for diagnosing, treating and preventing diseases, there are limitations.
Two resources, the Genetic Test Registry and GeneTests, contain information about the specific genetic tests offered by clinical laboratories. Genetic testing generally refers to the analysis of DNA to identify changes in genetic sequence (deletions, additions, or misspellings) or in expression levels. It can also refer to the analysis of RNA to determine gene expression, to biochemical tests to detect the presence of gene products (proteins), and to the microscopic analysis of chromosomes. Regardless of genetic test results, it is essential to talk to your doctor, medical geneticist, or genetic counselor about any questions or concerns you may have. You can also stay up-to-date on rapid advances in genetic knowledge with the American College of Medical Genetics and Genomics (ACMG) CME.
The steps you take after receiving a positive result will depend on why the genetic test was done. If you are being tested for an inherited genetic disorder, you should consider talking to your family about your decision to have genetic testing. Discuss all the risks and benefits of genetic testing with your doctor, a medical geneticist, or a genetic counselor before having a genetic test.