DNA Tests & Gene Testing

What are DNA tests?

DNA tests, or genetic tests, look for changes (variations) in your genes, chromosomes and DNA. This is also called gene testing. DNA tests can give you lots of information about your genetic makeup. They can often:

• Confirm if you have or don’t have a specific disease
• Determine if you have a higher risk of developing certain conditions
• Find out if you carry a specific altered gene that you can pass on to your child

If you’re interested in gene testing, you should speak to a genetic counselor. They can help you decide if DNA testing is right for you, and if it is, which kind. They’ll also be able to help you understand the results.

What are the different types of DNA tests?

Genetic tests may look at your genes, chromosomes and/or almost all of your genetic material, which is made up of DNA. Your healthcare provider will recommend certain tests based on several factors. These factors include your family history, medical history and any suspected genetic conditions.

Gene testing

Gene tests examine your genes to find changes that can cause or increase your risk of developing a genetic disease.

Gene tests include:

• Targeted single variant: Single variant testing looks for a specific change (variant) in one gene that’s known to cause a particular disorder. Your healthcare provider may use this test to determine if a genetic abnormality running in your biological family is found in you.
• Single gene: Single gene testing looks for any changes in one gene that’s known to cause a specific condition. Your provider may recommend single gene testing to confirm, or rule out, a diagnosis if you have symptoms of the condition or it runs in your family.
• Genetic testing panel: Gene panels look for changes in more than one gene. Genetic testing panels are used when changes in any of several genes can cause one or more symptoms that are found in you.

Genomic testing

Large-scale genomic tests look for changes throughout your DNA. Your provider may suggest genomic testing if other gene tests haven’t found a genetic reason for a condition. Or they may recommend it if you have a complex medical condition.

There are two kinds of genomic testing:

• Whole exome sequencing: Whole exome sequencing looks for changes in many of your genes.
• Whole genome sequencing: Whole genome sequencing looks at more than just genes — it looks at most of your genetic material/DNA.

Chromosomal testing

Chromosomal tests study your chromosomes — long strings of your DNA. This type of test looks for changes in your chromosomes instead of your genes. Chromosomal testing may find:

• An extra copy of a chromosome
• A missing copy of a chromosome
• An added piece of a chromosome (addition)
• A missing piece of a chromosome (deletion)
• A rearrangement of certain segments of chromosomes (translocation)

Gene expression testing

When a gene within a cell is active (turned on), it means the cell goes through the process of reading instructions and assembling a protein that will be expressed as a certain trait or condition.

Gene expression tests study the activity level of active genes. Certain conditions, including many kinds of cancer, may occur when a particular gene is too active (overexpression) or not active enough (underexpression).

What are DNA tests used for?

Gene testing has many valuable uses. They can offer important information about your DNA or the genetic background of a loved one. The uses of DNA tests include:

Prenatal testing

Your healthcare provider can detect changes in the genes or chromosomes of a fetus through a prenatal genetic test while you’re pregnant. Prenatal testing can determine the chance of your baby being born with certain medical conditions. If your baby has an increased risk of having a condition because of your family’s genetic history or because there are signs of a condition in the fetus itself, your provider may recommend this type of test.

Diagnostic testing

Diagnostic testing can confirm or rule out specific genetic disorders or chromosomal problems. But it doesn’t test for all genetic conditions. Healthcare providers often use diagnostic testing during pregnancy. But they can use it at any time to confirm a diagnosis if you have symptoms of a certain disease.

Carrier screening

If a condition is autosomal recessively inherited, it means that you can carry a gene for that condition, but not have symptoms. Carrier screening can tell you if you carry a copy of an altered gene for an autosomal recessive disease. If both parents are carriers for the same condition, there would be a 25% risk of passing that on to a child.

Providers offer this testing to everyone planning a pregnancy or who is in the early stages of pregnancy. While some families know that they have a history of a disease that is passed on in an autosomal recessive way, others may not.

Preimplantation testing

Preimplantation testing can find genetic changes in embryos made using assisted reproductive techniques (ART), like in vitro fertilization (IVF). Your provider takes a small number of cells from the embryos and tests them for certain changes. This way, you can make an informed choice about which embryos your provider will implant in your uterus to start a pregnancy.

Newborn screening

Newborn screening tests for certain genetic, metabolic or hormone-related conditions. Healthcare providers screen all newborns immediately after birth so treatment can start as soon as possible if they need it. In the U.S., hospitals can screen for up to 80 different medical conditions. Each state decides which diseases to screen for in newborns.

Predictive and pre-symptomatic testing

Your healthcare provider can sometimes use predictive and pre-symptomatic tests to look for genetic changes that increase your likelihood of developing a condition later in life. These include certain types of cancer. Genetic predisposition tests like BRCA testing look for mutations in the BRCA genes. Mutations in these genes can mean an increased risk of breast cancer and other cancers.

Pre-symptomatic tests can tell whether you’ll develop a genetic disease before you’ve had any symptoms. But not always with 100% certainty. So, speak with your provider about the risks and benefits.

Pharmacogenomic testing

Pharmacogenomics is a type of testing that looks for changes in your genetic makeup that may affect how your body processes certain medications. The test determines if a medication will work for you. If the test shows it will work, it can also predict the safest and most effective dose. This helps your healthcare provider choose the best treatment options for you.

What diseases can be detected through genetic testing?

It’s important to remember that while gene testing can find some conditions, it doesn’t detect everything. Also, a positive result doesn’t always mean you’ll develop a disease. But DNA tests can be useful to confirm or rule out many different diseases and conditions. These conditions include:

• Cystic fibrosis
• Down syndrome
• Familial adenomatous polyposis
• Hereditary breast cancer
• Hereditary colon (colorectal) cancer
• Huntington’s disease
• Juvenile polyposis syndrome
• MUTYH-associated polyposis
• Phenylketonuria
• Sickle cell disease

How does gene testing work?

Your healthcare provider will collect a sample of your blood, hair, skin, tissue or amniotic fluid. They’ll send the sample to a laboratory.

At the lab, a pathologist will look for changes in your genes, chromosomes and DNA. Then, they’ll send the test results to your provider.

What are the risks of DNA tests?

The physical risks of most DNA tests are small. Certain types of prenatal testing do carry a small risk of infection, bleeding and losing your pregnancy (miscarriage). This is because the test requires collecting a sample of amniotic fluid from around the fetus.

The greater risks of gene testing are emotional and financial. If you receive unexpected results, you may feel angry, scared, depressed, anxious or guilty. Also, gene testing can cost anywhere from hundreds to thousands of dollars. Insurance may cover the cost of gene testing, but it often depends on the type of test and the reason for it.

Gene testing doesn’t provide information about all possible genetic disorders either. And not all of them are 100% accurate. They also don’t necessarily tell you about how severe symptoms may be. And they don’t tell you when a certain genetic condition may develop.

Genetic testing results can sometimes also have implications for your ability to obtain certain types of insurance. Your genetic counselor should walk you through any of those concerns.

What do the results of DNA tests mean?

The results of DNA tests aren’t always straightforward. Your healthcare provider will use the type of test, your medical history and your family history to interpret them. Then, they’ll go over the specific results with you. The results may be any of the following:

• Positive: If a DNA test has a positive result, the lab found a genetic change known to cause a certain condition. This may confirm a diagnosis, identify you as a carrier of the disease or determine that you have an increased risk of the condition.
• Negative: If a DNA test has a negative result, the lab didn’t find a genetic change known to cause a certain condition. This may rule out a diagnosis, identify that you’re likely not a carrier of the disease or determine that you don’t have evidence of an increased risk of the condition.
• Uncertain: If a DNA test has an uncertain result, the lab may have found a genetic change. But they didn’t find enough information about it to determine whether it’s a harmless change or a disease-causing one. This is because everyone has normal, natural changes in their DNA that don’t affect their health.

How accurate are DNA tests?

Two measures of accuracy apply to gene testing:

• Analytical validity looks at whether DNA tests can accurately detect whether a specific gene has a change or not.
• Clinical validity asks, if there is a change, is it related to a specific disease or condition?

All labs that perform DNA tests that a genetic counselor or geneticist would recommend are regulated by federal and/or state standards. The standards are designed to ensure the accuracy of gene testing. Some direct-to-consumer (DTC) genetic testing companies don’t follow these same regulations.

How long does it take to get the results of DNA tests?

Some test results may only take a few days. Other tests can take several weeks to a month or two. Your healthcare provider will give you specific information regarding the timing of your test results.

If the results are abnormal, what are the next steps?

If a test result comes back positive, speak with your healthcare provider or a genetic counselor. They can further explain the results and provide you with next steps. Depending on the condition, your provider may request additional tests to learn more about the disease and determine treatment options.

Your provider may refer you to a specialist who’s an expert in the condition and can answer specific questions. Or you may work with a social worker, who’ll listen to your concerns and help guide you through the process.

What’s the best DNA testing kit?

You should try to find a healthcare provider or genetic counselor near you to perform gene testing. They’ll order the correct tests and then talk to you about what they mean.

Direct-to-consumer (DTC) genetic tests are risky if you don’t have anyone you can speak to personally about the results.

When did DNA testing start?

Scientists discovered a technique called “restriction fragment length polymorphism (RFLP)” analysis in the 1980s. This analysis became the first genetic test to use DNA. But in the 1990s, polymerase chain reaction (PCR) testing was introduced. This type of gene testing replaced RFLP testing. The science of gene testing is constantly changing.

What’s a DNA paternity test?

A DNA paternity test can determine a child’s biological father. You can figure out whether someone could be the biological father of your baby or child through a DNA cheek swab or blood test.