Rhode Island Department of Health Genetics Website

Genetic Screening and Testing

Gene testing involves examining a person's DNA for a flag associated with a disease or disorder. The DNA is usually taken from a blood sample, but sometimes it is taken from another body fluid or tissue. The tests can be used to look for possible predisposition to disease, or to confirm a suspected mutation in an individual or family. The DNA change can be relatively large: a missing or added piece of a chromosome - or even an entire chromosome - which is visible under a microscope. Or it can be extremely small, as little as one extra, missing, or altered chemical base. Genes can have too many copies (overexpressed), be inactivated or lost altogether. Sometimes, pieces of chromosomes become switched (transposed) so that a gene ends up in a location where it can’t work correctly. In addition to studying chromosomes or genes, genetic testing in a broader sense includes biochemical tests for certain proteins that signal faulty genes.

The most widespread type of genetic testing is newborn screening. Each year in the United States, four million newborn infants have blood samples tested for abnormal or missing gene products. Some tests look for abnormal arrangements of the chemical bases in the gene itself, while other tests detect inborn errors of metabolism (for example, phenylketonuria) by verifying the absence of a protein that the cell needs to function normally.

Carrier testing can be used to help couples to learn if they carry - and thus risk passing to their children - a recessive allele for inherited disorders such as cystic fibrosis, sickle-cell anemia, or Tay-Sachs disease . Genetic tests - biochemical, chromosomal, and DNA-based - also are widely available for the prenatal diagnosis of conditions such as Down syndrome. In clinical research programs, doctors make use of genetic tests to identify telltale DNA changes in cancer or precancer cells. Such tests can be helpful in several areas: early detection, diagnosis, prognosis and treatment.

Much of the current excitement in gene testing, however, centers on predictive gene testing: tests that identify people who are at risk of getting a disease, before any symptoms appear. Tests are already available in research programs for some two dozen such diseases, and as more disease genes are discovered, more gene tests can be expected.

Click on the following link to view a listing of the most current genetic tests available.