Genetic testing is a medical test that looks for changes — called variants or mutations — in your DNA, the genetic instructions in all living things. Most such changes do nothing, but sometimes even a small change can cause disease or another health condition.
What the tests examine
A sample of blood or tissue is checked for changes in:
| Target | What it is |
|---|---|
| Genes | Stretches of DNA that shape how you look and how your body works; many tell the body how to make proteins. Genome sequencing checks all your DNA; exome sequencing checks only the parts that code for proteins |
| Proteins | Molecules that do most of the work in cells. Changes in how much protein there is, or how active it is, may point to gene changes |
| Chromosomes | Threadlike structures of DNA wrapped tightly around proteins. People usually have 23 pairs |
Ways to get tested
- Clinical testing, through a health care provider — the usual route — to learn about an inherited disorder and guide care.
- Research-based testing, as part of a clinical trial.
- Direct-to-consumer testing, where you send in a DNA sample yourself to learn about ancestry or disease risk.
Tests usually use blood or a cheek swab, but can also use hair, saliva, skin, amniotic fluid or other tissue. A lab then uses one of several techniques to look for changes.
Why people are tested
- Before birth: to find genetic diseases in a fetus (prenatal testing), or to lower the risk of genetic disease in embryos created with assisted reproduction.
- Newborns: to screen for certain treatable conditions.
- Family planning: to learn whether you carry a gene you could pass to your children (carrier testing).
- Risk: to see whether you are at higher risk of a disease, such as one that runs in your family.
- Diagnosis: to diagnose a disease, or find genetic changes behind one you already have.
- Treatment: to help choose the best drug and dose (pharmacogenomic testing), or to monitor and manage a disease — for example, to find the best cancer treatment.
- Relationships: to confirm a child's biological father, or how much DNA you share with relatives.
- Curiosity and science: to explore traits such as hair color or dimples, learn about ancestry, or help researchers understand genes and genetic conditions.
Benefits
- Helping your provider recommend how to manage or monitor a genetic condition.
- More information for decisions about your health and your family's: if you're at risk, you might get screened earlier and more often or change your lifestyle; if you're not, you can discuss when checkups make sense. It can also inform decisions about having children.
- Finding genetic disorders early in life, so treatment can start sooner.
Drawbacks
The physical risks are small, but there can be emotional, social and financial costs:
- Results can leave you angry, depressed, anxious or guilty, especially for a disease without good treatment.
- You may worry about genetic discrimination in jobs or insurance, despite protections.
- Tests may say little about whether you'll have symptoms, how severe a disease will be, or whether it will get worse.
- Results can be inconclusive.
- Tests can turn up unexpected findings, such as a risk for something other than what you were tested for.
- Some tests are expensive, and insurance may cover only part — or none — of the cost.
Deciding
The decision is complex. Besides talking with your provider, you can see a genetic counselor, a professional with specialized training in genetics and counseling, who can explain the tests, help you weigh risks and benefits, interpret results and make sure you have support.
Sources
Based on the MedlinePlus health topic "Genetic Testing," National Library of Medicine; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from medlineplus.gov
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