Just two decades ago, widespread genetic testing was a dream. Before the completion of the Human Genome Project in 2003, tests were largely limited to major chromosomal disorders like Down Syndrome, and couldn’t identify smaller, gene-level mutations. Today, though, anyone can order genetic tests through the mail, while doctors turn to genetic testing to diagnose even the rarest conditions. Still, that doesn’t mean everyone should be tested.
Many people can benefit from genetic testing, but it needs to be offered under the right circumstances and with appropriate guidance in order for these tests to be meaningful. Before sending away for a test or asking your doctor for genetic testing, here’s what you need to know.
One of the most common forms of genetic testing today is prenatal testing. These are tests performed on a fetus, typically early on in pregnancy, and can be done in several ways. Historically, prenatal testing relied on amniocentesis, a somewhat invasive procedure for directly sampling fetal DNA. However, there’s now a newer, non-invasive test called cell-free DNA testing performed using a sample of the mother’s blood.
Prenatal genetic testing doesn’t look for every condition but typically checks for Down Syndrome, trisomy 13, and trisomy 18. Depending on family history and carrier testing – testing of parental genetics – these tests may also look for conditions like Tay-Sachs, a fatal childhood condition often found in Ashkenazi Jews, cystic fibrosis, and sickle cell disease. Because of the risks involved in amniocentesis, which can occasionally cause a miscarriage, most doctors only recommend prenatal genetic testing for women over 35, or if you have other risk factors, such as a history of certain genetic disorders, a history of stillbirth or repeated miscarriage, or if you’ve previously had a premature birth or child with a genetic condition.
Unlike prenatal testing, newborn genetic testing is standard, and it’s completely non-invasive. What tests are administered, however, varies by state – according to YourDNA.com, states independently determine their protocols based on the Recommended Uniform Screening Panel (RUSP).
During newborn genetic testing, infants are given a simple heel prick test and are also screened for a number of metabolic disorders. Among the most common conditions these programs screen for are cystic fibrosis, phenylketonuria (PKU), spinal muscular atrophy (SMA), and severe combined immunodeficiency, along with several dozen additional disorders. Most states require these tests be done within the first few days after birth, with follow up testing within the next few weeks.
Why is genetic testing standard for newborns when it’s otherwise uncommon? There are several reasons. First, many of the conditions can be fatal or lead to significant health issues within the first months or years of life. Children with PKU, for example, need to be on a phenylalanine-free diet to prevent brain damage. Healthcare professionals estimate that for every dollar spent on infant genetic testing, they save $2 to $4 on later health costs. Infant testing is front-line preventative care.
Beyond infancy, the occasions for genetic testing become scarcer – not in the sense that it’s unavailable, but rather in that it’s less likely to be called upon. Yes, genetic testing can provide major health insights, but the information isn’t as precise as many people think. For example, DNA testing can provide information regarding hereditary cancer risks, and they may be appropriate if you have a family history of certain cancers. Your doctor may also recommend testing if you have a long history of unexplained symptoms that could be explained by a rare or underdiagnosed genetic condition.
One major concern with predictive genetic testing in adults is that it’s exactly that – predictive – and we often see spikes in testing when a celebrity reveals their own health history. When Angelina Jolie wrote about undergoing a prophylactic mastectomy and later a risk-reducing salpingo-oophorectomy (the removal of the fallopian tubes and ovaries) because she tested positive for the BRCA1 gene, doctors saw increased demand for the test. But while BRCA1 and BRCA2 both substantially increase breast and ovarian cancer risk, as well as potentially unnecessary surgeries and health anxiety.
As noted in the above discussion of prenatal testing, adults may also undergo genetic testing as a carrier screening before attempting to have children, and there are different screening practices for different groups. Doctors may offer specific ethnic screenings based on in-group risks, while others may receive broader pan-ethnic screening. Carrier screening can be especially valuable if you don’t know your family’s medical history because of adoption or estrangement.
What Else Should You Know?
If you’re considering genetic testing, one of the most important things to consider is how much guidance you’ll have in interpreting the results. Many direct-to-consumer “ancestry” tests, for example, also come with health information, but what they don’t come with is the support of a genetic counselor. Indeed, this is one reason that many medical professionals believe direct-to-consumer testing does more harm than good. This can be mitigated through appropriate genetic counseling, but most of these companies don’t provide that sort of post-testing support.
Genetics is a complex field, which is why it’s important to work with medical professionals to select the most appropriate tests and even to determine if testing is right for you. Many conditions have more than one test, and individuals without symptoms or family history typically shouldn’t pursue any kind of testing.
As genetic testing becomes more precise and we identify more genes for different diseases, guidelines will change – in many ways, the field is still in its infancy. Right now, though, testing often offers an incomplete picture because the presence of a gene is not the same as the presence of the disease. Such one-to-one correlations are actually quite uncommon in human genetics.
Genetic testing has helped millions of people make better-informed decisions about their health, get necessary medical treatment, and take preventative measures, and they undeniably offer immense benefit. At the end of the day, though, genetic testing is still a branch of medicine. You don’t prescribe your own medications or perform your own surgery, and you should have just as much professional guidance when considering genetic testing as you would for any other medical test or procedure. You can’t go it alone.