Frequently Asked Questions
Genetic testing is a type of medical test that identifies changes in chromosomes, genes, or proteins. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person’s chance of developing or passing on a genetic disorder.1 Genes are the DNA instructions you inherit from your mother and your father.2
There are many different types of genetic tests. Genetic tests can help to:
- Diagnose disease
- Identify gene changes that are responsible for an already diagnosed disease
- Determine the severity of a disease
- Guide doctors in deciding on the best medicine or treatment to use for certain individuals
- Identify gene changes that may increase the risk to develop a disease
- Identify gene changes that could be passed on to children
- Screen newborn babies for certain treatable conditions
Genetic test results can be hard to understand, however specialists like geneticists and genetic counselors can help explain what results might mean to you and your family. Because genetic testing tells you information about your DNA, which is shared with other family members, sometimes a genetic test result may have implications for blood relatives of the person who had testing.2
Genetic counselors have advanced training in medical genetics and counseling to guide and support patients seeking more information about how inherited diseases and conditions might affect them or their families, and to interpret test results.
You may be referred to a genetic counselor by a doctor (such as an obstetrician, oncologist or medical geneticist) to discuss your family history and genetic risks before or after having genetic testing. While genetic counselors are not medical doctors, they are part of your healthcare team and work with you and your doctor to help you understand:
- Your genetic risks based on your family history
- Your genetic risks for certain diseases or cancer
- Whether genetic testing might be right for you
- What the results of genetic tests may mean for you and your family
With expertise in counseling, genetic counselors can also provide emotional support as you make decisions and empower you with information for your overall healthcare.3
- Diagnostic testing is used to precisely identify the disease that is making a person ill. The results of a diagnostic test may help you make choices about how to treat or manage your health.
- Predictive and pre-symptomatic genetic tests (also called “proactive genetic testing”) are used to find gene changes that increase a person’s likelihood of developing diseases. The results of these tests provide you with information about your risk of developing a specific disease. Such information may be useful in decisions about your lifestyle and healthcare.
- Carrier testing is used to find people who “carry” a change in a gene that is linked to disease. Carriers may show no signs of the disease; however, they have the ability to pass on the gene change to their children, who may develop the disease or become carriers themselves. Some diseases require a gene change to be inherited from both parents for the disease to occur. This type of testing usually is offered to people who have a family history of a specific inherited disease or who belong to certain ethnic groups that have a higher risk of specific inherited diseases.
- Prenatal testing is offered during pregnancy to help identify fetuses that have certain diseases.
- Newborn screening is used to test babies one or two days after birth to find out if they have certain diseases known to cause problems with health and development.
- Pharmacogenomic testing gives information about how certain medicines are processed by an individual’s body. This type of testing can help your healthcare provider choose the medicines that work best with your genetic makeup.
- Research genetic testing is used to learn more about the contributions of genes to health and to disease. Sometimes the results may not be directly helpful to participants, but they may benefit others by helping researchers expand their understanding of the human body, health, and disease.2
With so many companies offering direct-to-consumer genetic testing, it can be challenging to determine which tests will be most informative and helpful to you. When considering testing, think about what you hope to get out of the test. Some direct-to-consumer genetic tests are very specific (such as paternity tests), while other services provide a broad range of health, ancestry, and lifestyle information.
Major types of direct-to-consumer genetic tests include:
- Disease risk and health – The results of these tests estimate your genetic risk of developing several common diseases, such as celiac disease, Parkinson disease, and Alzheimer disease. Some companies also include a person’s carrier status for less common conditions, including cystic fibrosis and sickle cell disease. A carrier is someone who has one copy of a gene mutation that, when present in to copies, causes a genetic disorder. The tests may also look for genetic variations related to other health-related traits, such as weight and metabolism (how a person’s body converts the nutrients from food into energy).
- Ancestry or genealogy – The results of these tests provide clues about where a person’s ancestors might have come from, their ethnicity, and genetic connections between families.
- Kinship – The results of these tests can indicate whether tested individuals are biologically related to one another. For example, kinship testing can establish whether one person is the biological father of another (paternity testing). The results of direct-to-consumer kinship tests, including paternity tests, are usually not admissible in a court of law.
- Lifestyle – The results of these tests claim to provide information about lifestyle factors, such as nutrition, fitness, weight loss, skincare, sleep, and even your wine preferences, based on variations in your DNA. Many of the companies that offer this kind of testing also sell services, products, or programs that they customize on the basis of your test results.
Before choosing a direct-to-consumer genetic test, find out what kinds of health, ancestry, or other information will be reported to you. Think about whether there is any information you would rather not know. In some cases, you can decline to find out specific information if you tell the company before it delivers your results.1
For a price (typically several hundred to a thousand dollars) you can order a genetic testing kit online or by phone. You’ll swab your cheek or spit into a test tube. Then you will mail it to a lab where it may be tested for a wide variety of things – from whether you inherited your intolerance to the lactose in dairy products to your risk of certain types of cancer to if you carry a gene for a serious illness such as cystic fibrosis and could pass it on to your children.
There are at-home tests for:
- Traits (e.g., male hair loss to dimples)
- Wellness (e.g., risk of certain types of cancer to restless leg syndrome)
- Ancestry reports (i.e., ethnicity and lineage)
- Carrier status (e.g., Tay-Sachs Disease to Sickle Cell Anemia)
- Paternity testing (i.e., determining a child’s biological father)
There are three general ways to get genetic testing:
- Through your physician or a genetic counselor – These are the most detailed and comprehensive tests available. They include cancer testing and testing for genetic disorders. They include large “panels,” meaning they test for the most genes.
- Physician-ordered online testing – While you can order some of the more comprehensive tests online, you will still need a physician’s approval. In some cases, your physician can order the test. In some cases, the testing company employs a physician who can order the test for you.
- Direct-to-consumer testing – These are the at-home tests you most often hear about. They do not require a physician’s order. However, they don’t fall under the same guidelines as the other two types of testing, and they may provide incomplete information. For example, they may not test for the genes you’re most interested in. Or they provide you raw data, but don’t provide guidance regarding the results and what they may mean for you or your family.
Receiving the results may produce a variety of emotions. You may be surprised, relieved, disappointed or confused. Whether you choose at-home testing or seek out testing through a medical professional, seeing a genetic counselor can provide helpful guidance.3
There are many reasons that people might get genetic testing. Doctors might suggest a genetic test if patients or their families have certain patterns of disease. Genetic testing is voluntary and the decision about whether to have genetic testing is complex.
A geneticist or genetic counselor can help families think about the benefits and limitations of a particular genetic test. Genetic counselors help individuals and families understand the scientific, emotional, and ethical factors surrounding the decision to have genetic testing and how to deal with the results of those tests.2
- Benefits: Genetic testing may be beneficial whether the test identifies a mutation or not. For some people, test results serve as a relief, eliminating some of the uncertainty surrounding their health. These results may also help doctors make recommendations for treatment or monitoring, and give people more information for making decisions about their and their family’s health, allowing them to take steps to lower his/her chance of developing a disease. For example, as the result of such a finding, someone could be screened earlier and more frequently for the disease and/or could make changes to health habits like diet and exercise. Such a genetic test result can lower a person’s feelings of uncertainty, and this information can also help people to make informed choices about their future.
- Drawbacks: Genetic testing has a generally low risk of negatively impacting your physical health. However, it can be difficult financially or emotionally to find out your results.
- Emotional: Learning that you or someone in your family has or is at risk for a disease can be scary. Some people can also feel guilty, angry, anxious, or depressed when they find out their results.
- Financial: Genetic testing can cost anywhere from less than $100 to more than $2,000. Health insurance companies may cover part or all of the cost of testing.
- Discrimination: Many people are worried about discrimination based on their genetic test results. In 2008, Congress enacted the Genetic Information Nondiscrimination Act (GINA) to protect people from discrimination by their health insurance provider or employer. GINA does not apply to long-term care, disability, or life insurance providers. (For more information about genetic discrimination and GINA, see http:/www.genome.gov/10002328/genetic-discrimination-fact-sheet/).
- Limitations of testing: Genetic testing cannot tell you everything about inherited diseases. For example, a positive result does not always mean you will develop a disease, and it is hard to predict how severe symptoms may be. Geneticists and genetic counselors can talk more about what a particular test will or will not tell you, and can help you decide whether to undergo testing.2
Genetic discrimination occurs when people are treated differently by their employer or insurance company because they have a gene mutation that causes or increases the risk of an inherited disorder. Fear of discrimination is a common concern among people considering genetic testing.
Several laws at the federal and state levels help protect people against genetic discrimination. In particular, a federal law called the Genetic Information Nondiscrimination Act (GINA) is designed to protect people from this form of discrimination.
GINA has two parts: Title I, which prohibits genetic discrimination in health insurance, and Title II, which prohibits genetic discrimination in employment. Title I makes it illegal for health insurance providers to use or require genetic information to make decisions about a person’s insurance eligibility or coverage. This part of the law went into effect on May 21, 2009. Title II makes it illegal for employers to use a person’s genetic information when making decisions about hiring, promotion, and several other terms of employment. This part of the law went into effect on November 21, 2009.
GINA and other laws do not protect people from genetic discrimination in every circumstance. For example, GINA does not apply when an employer has fewer than 15 employees. GINA also does not protect against genetic discrimination in forms of insurance other than health insurance, such as life, disability, or long-term care insurance.1
Once a person decides to proceed with genetic testing, a medical geneticist, primary care doctor, specialist, or nurse practitioner can order the test. Genetic testing is often done as part of a genetic consultation.
Genetic tests are performed on a sample of blood, hair, skin, amniotic fluid, or other tissue. For example, a procedure called a buccal smear uses a small brush or cotton swab to collect a sample of cells from the inside surface of the cheek. The sample is sent to a laboratory where technicians look for specific changes in chromosomes, DNA, or proteins, depending on the suspected disorder. The laboratory reports the test results in writing to a person’s doctor or genetic counselor, or directly to the patient if requested.
Before a person has a genetic test, it is important that he or she understands the testing procedure, the benefits and limitations of the test, and the possible consequences of the test. The process of educating a person about the test and obtaining permission is called “informed consent.”1
Before a person has a genetic test, it is important that he or she fully understands the testing procedure, the benefits and limitations of the test, and the possible consequences of the test results. The process of educating a person about the test and obtaining permission to carry out testing is called “informed consent.” “Informed” means that the person has enough information to make an educated decision about testing; “consent” refers to a person’s voluntary agreement to have the test done.
In general, informed consent can only be given by adults who are competent to make medical decisions for themselves. For children and others who are unable to make their own medical decisions (such as people with impaired mental status), informed consent can be given by a parent, guardian, or other person legally responsible for making decisions on that person’s behalf.
Informed consent for genetic testing is generally obtained by a doctor or genetic counselor. The healthcare provider will discuss the test and answer any questions. If the person wishes to have the test, he or she will then usually read and sign a consent form. Informed consent is not a contract, so a person can change his or her mind at any time after giving initial consent. A person may choose not to go through with genetic testing even after the test sample has been collected. A person simply needs to notify the healthcare provider if he or she decides not to continue with the testing process.1
The results of genetic tests are not always straightforward, which often makes them challenging to interpret and explain. Therefore, it is important for patients and their families to ask questions about the potential meaning of genetic test results both before and after the test is performed. When interpreting test results, healthcare professionals consider a person’s medical history, family history, and the type of genetic test that was done.
A positive test result means that the laboratory found a change in a particular gene, chromosome, or protein of interest. Depending on the purpose of the test, this result may confirm a diagnosis, indicate that a person is a carrier of a particular genetic mutation, identify an increased risk of developing a disease (such as cancer) in the future, or suggest a need for further testing. Because family members have some genetic material in common, a positive test result may also have implications for certain blood relatives of the person undergoing testing. It is important to note that a positive result of a predictive or presymptomatic genetic test usually cannot establish the exact risk of developing a disorder. Also, health professionals typically cannot use a positive test result to predict the course or severity of a condition.
A negative test result means that the laboratory did not find a change in the gene, chromosome, or protein under consideration. This result can indicate that a person is not affected by a particular disorder, is not a carrier of a specific genetic mutation, or does not have an increased risk of developing a certain disease. It is possible, however, that the test missed a disease-causing genetic alteration because many tests cannot detect all genetic changes that can cause a particular disorder. Further testing may be required to confirm a negative result.
In some cases, a test result might not give any useful information. This type of result is called uninformative, indeterminate, inconclusive, or ambiguous. Uninformative test results sometimes occur because everyone has common, natural variations in their DNA, called polymorphisms, that do not affect health. If a genetic test finds a change in DNA that has not been associated with a disorder in other people, it can be difficult to tell whether it is a natural polymorphism or a disease-causing mutation. An uninformative result cannot confirm or rule out a specific diagnosis, and it cannot indicate whether a person has an increased risk of developing a disorder. In some cases, testing other affected and unaffected family members can help clarify this type of result.1
In many cases, health insurance plans will cover the costs of genetic testing when it is recommended by a person’s doctor. Health insurance providers have different policies about which tests are covered, however. A person may wish to contact his or her insurance company beforehand to ask about coverage.1
Some people may choose to pay for genetic testing directly out-of-pocket rather than going through their insurance policy. Financial assistance for genetic testing of the uninsured or underinsured is sometimes available through the company performing the genetic testing.
Circulating tumor DNA (ctDNA) is found in the bloodstream and refers to DNA that comes from cancerous cells and tumors. Most DNA is inside a cell’s nucleus. As a tumor grows, cells die and are replaced by new ones. The dead cells get broken down and their contents, including DNA, are released into the bloodstream. ctDNA are small pieces of DNA, usually comprising fewer than 200 building blocks (nucleotides) in length.
The quantity of ctDNA varies among individuals and depends on the type of tumor, its location, and for cancerous tumors, the cancer stage.
Detection of ctDNA can be helpful in the following cases:
- Detecting and diagnosing a tumor. Because tumor DNA has acquired multiple genetic mutations, leading to tumor development, ctDNA is not an exact match to the individual’s DNA. Finding DNA with genetic differences aids in tumor detection. Diagnosing the type of tumor using ctDNA can reduce the need for getting a sample of the tumor tissue (tumor biopsy), which can be challenging when a tumor is difficult to access, such as a tumor in the brain or lung.
- Guiding tumor-specific treatment. Analyzing the genome of tumor cells using ctDNA can help doctors determine which treatment will be most effective. Currently, however, approval from the FDA for ctDNA testing to personalize cancer treatment is limited.
- Monitoring treatment. A decrease in the quantity of ctDNA suggests the tumor is shrinking and treatment is successful.
- Monitoring periods with no symptoms (remission of cancer). A lack of ctDNA in the bloodstream indicates that the cancer has not returned.1
Genetic ancestry testing, or genetic genealogy, is a way for people interested in family history (genealogy) to go beyond what they can learn from relatives or from historical documentation. Examination of DNA variations can provide clues about where a person’s ancestors might have come from and about relationships between families. Certain patterns of genetic variation are often shared among people of particular backgrounds. The more closely related two individuals, families, or populations are, the more patterns of variation they typically share.
Three types of genetic ancestry testing are commonly used for genealogy:
- Y chromosome testing – Variations in the Y chromosome, passed exclusively from father to son, can be used to explore ancestry in the direct male line. Y chromosome testing can only be done on males, because females do not have a Y chromosome. However, women interested in this type of genetic testing sometimes recruit a male relative to have the test done. Because the Y chromosome is passed on in the same pattern as are family names in many cultures, Y chromosome testing is often used to investigate questions such as whether two families with the same surname are related.
- Mitochondrial DNA testing – This type of testing identifies genetic variations in mitochondrial DNA. Although most DNA is packaged in chromosomes within the cell nucleus, cell structures called mitochondria also have a small amount of their own DNA (known as mitochondrial DNA). Both males and females have mitochondrial DNA, which is passed on from their mothers, so this type of testing can be used by either sex. It provides information about the direct female ancestral line. Mitochondrial DNA testing can be useful for genealogy because it preserves information about female ancestors that may be lost from the historical record because of the way surnames are often passed down.
- Single nucleotide polymorphism testing – These tests evaluate large numbers of variations (single nucleotide polymorphisms or SNPs) across a person’s entire genome. The results are compared with those of others who have taken the tests to provide an estimate of a person’s ethnic background. For example, the pattern of SNPs might indicate that a person’s ancestry is approximately 50 percent African, 25 percent European, 20 percent Asian, and 5 percent unknown. Genealogists use this type of test because Y chromosome and mitochondrial DNA test results, which represent only single ancestral lines, do not capture the overall ethnic background of an individual.
Genetic ancestry testing has a number of limitations. Test providers compare individuals’ test results to different databases of previous tests, so ethnicity estimates may not be consistent from one provider to another. Also, because most human populations have migrated many times throughout their history and mixed with nearby groups, ethnicity estimates based on genetic testing may differ from an individual’s expectations. In ethnic groups with a smaller range of genetic variation due to the group’s size and history, most members share many SNPs, and it may be difficult to distinguish people who have a relatively recent common ancestor, such as fourth cousins, from the group as a whole.
Genetic ancestry testing is offered by several companies and organizations. Most companies provide online forums and other services to allow people who have been tested to share and discuss their results with others, which may allow them to discover previously unknown relationships.1
1Courtesy of the U.S. National Library of Medicine; www.nlm.nih.gov, www.ghr.nlm.nih.gov
2Courtesy of the National Human Genome Research Institute; www.genome.gov
3Courtesy of the National Society of Genetic Counselors; www.nsgc.org
2Courtesy of the National Human Genome Research Institute;
3Courtesy of the National Society of Genetic Counselors;