What Is Genetic Testing?

Genetic testing is a type of medical testing process that is used to detect genetic mutations, or variations in your DNA, chromosomes, or proteins, that are associated with genetic disorders. It serves purposes like diagnosis, predicting disease risk, assessing carrier status, prenatal screening, and studying how the human body reacts to certain medications.

Genetic tests are conducted by sending samples of blood, saliva, or tissue to a laboratory for clinical evaluation. The results of genetic testing can provide valuable information for medical diagnosis, treatment planning, reproductive decision-making, and assessing your risk of genetic or hereditary conditions.

Purpose

There are several reasons your healthcare provider, genetic counselor, and medical geneticist (a medical doctor who specializes in genes) might call for a genetic test.

Detecting Diseases in Newborns

Genetic tests are part of the panel of the standard tests newborns undergo about two to three days after birth. It is performed by testing blood samples collected from the heel. These tests help healthcare providers screen for genetic disorders that are treatable with early intervention.

Assisting in Diagnosis

Healthcare providers also use genetic tests to confirm or rule out certain chromosomal or genetic disorders if you have symptoms, such as Huntington’s disease or cystic fibrosis. Prenatal tests assist in the diagnosis of certain diseases in developing fetuses during pregnancy.

Determining If You’re a Carrier of a Disease 

Carrier testing determines if you and/or your partner are carriers for various genes. Being a carrier means that you have—or "carry"—a gene or gene mutation that can lead to your child developing a condition, even though you may not have the condition yourself. Depending on the condition, you or your partner may be able to pass on a condition if only one of you has the gene. In some cases, both of you need to carry a gene to have the potential of passing it on.

Your healthcare provider might recommend carrier testing if you have a family history of such a condition or if you belong to an ethnic group that has increased risk of developing one.

Determining Your Family History

You may not know your family medical history for a variety of reasons, including adoption, loss of records, estrangement, and loss of family early in life, among other factors. Your family medical history can provide valuable information for all areas of your health, so completing genetic testing can help fill in the gaps where needed.

Assessing Risk of Developing Genetic Disorders

Prenatal testing, or amneocentesis, can also be performed to screen for gene or chromosome mutations and assess the risk of developing certain genetic disorders, such as Down syndrome or another chromosomal disorder.

Supporting In-Vitro Fertilization

Assisted reproduction technology like in-vitro fertilization (IVF), in which an egg and sperm are fertilized in a test tube, helps people with fertility problems get pregnant. Samples of fertilized embryos can be tested for certain genetic diseases.

Identifying Your Risk of Other Diseases

Some genetic disorders develop later in life. Genetic testing can help to determine if you are at risk for one of these conditions before symptoms begin This predictive or pre-symptomatic genetic testing detects conditions like hemochromatosis (an inability to digest iron) or some types of cancer.

Determining How Well Medications Will Work

Genetic sequencing can also help your healthcare provider determine how effective medications you’re taking are or how well a medication is expected to work. Genetic mutations can also indicate an increased risk for adverse events or side effects from a medication.

Forensic Testing

This is genetic testing that’s used to establish identity, rather than to diagnose or assess risk. It assists in criminal investigations or to determine parenthood.

Types of Genetic Testing

Currently, there over 77,000 genetic tests. These can be divided into three types, each with specific applications, advantages, and disadvantages: cytogenic, biochemical, and moclecular testing.

Genetic or Molecular Testing

This type of testing screens for changes in the genes, themselves—a technique called sequencing. They are used for determining your risk for certain diseases or confirming a diagnosis. Overall, the scope of these genetic tests varies; they might look for a specific nucleotide (a DNA building block), one or multiple genes, or the whole genome (your entire genetic make-up).

Cytogenic Testing

Cytogenic testing detects changes or problems in your chromosomes, the thread-like nuclei within your cells that carries your genetic information. A normal human cell has 23 pairs of chromosomes, and these tests can help determine if there are one or more extra chromosomes (aneuploidy) or any missing chromosomes Having an extra chromosome or a missing chromosome can be a cause of many different conditions.

Biochemical Testing

This type of genetic testing assess the how active certain proteins and enzymes are. Abnormal results may indicate an increased risk for certain genetic disorders.

How Does It Work?

Your healthcare provider, genetic counselor, or medical geneticist will determine which genetic test you need based on your health status, health history, and family history. To perform a genetic test, samples are collected for examination. These may include blood, saliva, amniotic fluid (during pregnancy), hair, a tumor, or a scraping from inside the cheek.

These are sent off to clinical laboratories for evaluation, where they can be analyzed using a range of techniques to identify any genetic, chromosomal, or biochemical abnormalities.

Before the Test

When coming in, be prepared to answer questions about your and your family’s health history, as well as any symptoms you have. You don’t need to do anything special to prepare before a sample collection, and in most cases, the procedure is quick, taking five minutes. However, prenatal genetic testing takes longer, about 30 minutes.

During the Test

There are several ways that samples can be collected for genetic testing:

• Blood sample: If testing a sample of blood, the person taking the sample will typically have you sit in an exam room and roll up a sleeve. They’ll then use a syringe to prick you and access a vein or artery for collection, clean the area, and place a bandage at the site.
• Buccal smear: Some types of tests require swabbing or scraping of tissue from the inner cheek using a small brush or swab.
• Newborn screening: To test newborns, a small sample of blood is collected by pricking the infant's heel.
• Prenatal screening: An ultrasound is used to guide the collection of amniotic fluid or placenta tissue, which surround developing fetuses. You lie back on an operating table, your healthcare provider will rub a gel on your belly, then move an ultrasound device over the area. They then guide a syringe through your abdomen to collect a sample.

After the Test

In most cases when a sample is taken, you'll be able to go home right afterward. For prenatal screening, your healthcare provider may keep you for a bit to monitor the heartbeat and activity of the fetus to ensure everything’s OK. You won’t need to make special travel arrangements to go home.

You’ll need to make an appointment for genetic counseling once the results come in. At this appoint, a genetic counselor or geneticist will explain the results and inform you about your options going forward.

Often, one test is sufficient, though you may need additional testing if your results are inconsistent with any symptoms you're experiencing. In addition, genetic testing may help track the progress of an existing disease.

Risks and Precautions

Largely, genetic testing procedures, especially blood or cheek tissue collection, pose little physical risk. Some may feel some soreness or tenderness afterward. In rare cases, the collection site can become infected. Seek emergency care if you experience swelling at the sample site, excess pain, and fever.

Prenatal genetic testing procedures also have a strong track-record of safety. That said, there’s a 0.11% chance of miscarriage with amniocentesis, the risk of which rises if you’re already at a higher risk of complications.

In rare cases, it also causes amniotic fluid leak, vaginal bleeding, damage to the fetus’s eyes or cord, or lead to birth defects. Following amniocentesis, you may also feel some soreness or experience cramping in your abdomen. If you experience side effects, let your healthcare provider know.

Genetic testing can also be an emotional process, especially if you receive unhappy news. This can cause feelings of distress, depression, anxiety, or guilt. You may also feel concerned about the stigma of having certain diseases and how that may impact insurance and work.

How to Prepare for Genetic Testing

Samples collections for genetic testing occur in hospitals, clinics, or specialist offices. Generally, you won’t have to restrict your diet or avoid food or drink before sample collection. It’s probably best to wear comfortable clothes that allow easy access for collection.  

When you arrive, be sure to have the following insurance information, a list of medications you’re taking, and a means of payments.

Whether insurance covers your test depends on if it’s considered a medical necessity. Talk to your healthcare and insurance provider to learn how much you’ll need to pay.  

Informed Consent

Genetic tests are voluntary, and the decision to take one is yours. Your provider will need to establish “informed consent,” which means they’ve given you the information you need to make an informed choice. Before starting, you’ll also need to sign a form acknowledging that your provider has explained:

• How the procedure is done
• The potential benefits and drawbacks of the test
• The potential emotional and/or physical risks of the test
• How the results will be used, such as whether they’ll be used for research
• What the results mean, whether positive, negative, or inconclusive
• If the results can tell you information about the health of relatives or children

Results

The amount of time it takes before you get results varies, ranging anywhere from a couple of days to two weeks. Notably, you may not receive newborn screening results if diseases aren’t found.

Because the information that’s found is complex, you’ll need to come in for a counseling appointment to discuss and interpret your results. This can be done in-person, via phone-consultation, or in a video meeting.

Interpreting Your Results

Since genetic testing can tell you a wide range of information, the results can mean different things:

• Positive result: A positive result means genetic mutations, genes, or chromosomal abnormalities have been found. This might confirm a diagnosis, indicate you’re a carrier of a disease-causing gene, or show that you or your fetus have higher risk of disease. This information helps determine effective treatments, lifestyle changes or preventive measures, or decisions about pregnancy.
• Negative result: Negative results means no abnormalities were seen in the genes or chromosomes. It means you may not be affected by a certain disease, aren’t a carrier of disease-causing gene, or that your fetus isn’t at risk. However, because genetic tests can miss certain genes, you’ll likely need a second test to confirm negative results.
• Inconclusive result: Sometimes, the results are neither positive nor negative. This may be because mutations were only found in genes not associated with the health issue in question. Inconclusive results can neither confirm nor rule out a diagnosis, and it can’t tell you if or your fetus are at higher risk of disease. In these cases, comparing your results with a blood relative may help, and your healthcare provider can perform other tests to determine the cause of symptoms, if relevant.

A Quick Review

Genetic testing helps healthcare providers diagnose certain genetic diseases, assess your risk for cancer or other conditions, and determine if you’re carrying a gene mutation. They do so by clinically identifying specific genes, chromosomes, and proteins from samples of blood, saliva, cheek tissue, placenta, or amniotic fluid (surrounding a fetus).

There are few physical risks with genetic testing; however, prenatal genetic screening, in less than 1% of cases, can raise your risk of miscarriage. You’ll need genetic counseling to understand your results and learn about your options. The choice to take a genetic test is a personal one; talk to your healthcare provider if you’re considering this option.