If you have a health condition that is difficult to diagnose, or a family history of medical problems, your doctor might recommend genetic sequencing for additional clues. Whole exome sequencing is a type of genetic sequencing increasingly used to understand what may be causing symptoms or a disease. Genetic testing has already been used for a long time in some health areas, such as cancer diagnosis and prenatal screening.
"Genetics," "DNA," and "exome" (explained below) are terms that appear more frequently in health care news as personalized medicine inches closer to reality. (The goal of personalized medicine is to prescribe medicine and treatment that is tailored to your genetic makeup.) Exome sequencing has the potential to play a big role.
Technical words aside, the process of exome sequencing is straightforward. "It's helpful to think of a person's genome as an instructional manual that directs the body's processes," says Saquib Lakhani, MD, clinical director of the Yale Medicine Pediatric Genomics Discovery Program (PGDP). "You can think of chromosomes as chapters within the manual; genes as the sentences, and DNA as individual letters. Exome sequencing is like running a spell check program."
At Yale Medicine, this "check" is done at the Yale Center for Genome Analysis, a CLIA-certified laboratory, by experts who specialize in sequencing patient exomes from samples of saliva or blood. They then provide the results to geneticists, bioinformaticians, and researchers, who comb through the data looking for unusual genetic mutations. Usually, a patient's physician will then collaborate with this group to interpret results and relay information back to the patient.
At present, exome sequencing is only available by referral from your doctor or for patients involved in clinical trial studies. As exome sequencing becomes more common, though, its costs will likely drop and its availability will increase. This type of test could join the ranks of routine genetic tests already widely available now.