What do the results of genetic tests mean?
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 negative 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.
For more information about interpreting genetic test results:
The Department of Energy, Office of Science offers information about evaluating gene tests (http://www.ornl.gov/sci/techresources/Human_Genome/resource/ testeval.shtml).
GeneTests provides a brief discussion of interpreting test results (http://www.ncbi.nlm.nih.gov/projects/GeneTests/static/concepts/primer/ primerordertest.shtml#testresult) and a sample laboratory report (http://www.ncbi.nlm.nih.gov/projects/GeneTests/static/concepts/primer/ labreport.shtml) for a genetic test.
The National Women's Health Resource Center offers a list of questions about genetic testing (http://www.healthywomen.org/condition/genetic-testing#hc-tab-1), including the meaning of test results, that patients and families can ask their healthcare professional.
What is the cost of genetic testing, and how long does it take to get the results?
The cost of genetic testing can range from under $100 to more than $2,000, depending on the nature and complexity of the test. The cost increases if more than one test is necessary or if multiple family members must be tested to obtain a meaningful result. For newborn screening, costs vary by state. Some states cover part of the total cost, but most charge a fee of $15 to $60 per infant.
From the date that a sample is taken, it may take a few weeks to several months to receive the test results. Results for prenatal testing are usually available more quickly because time is an important consideration in making decisions about a pregnancy. The doctor or genetic counselor who orders a particular test can provide specific information about the cost and time frame associated with that test.
For more information about the costs and turnaround time for genetic tests:
GeneTests provides a list of factors that influence the turnaround time and costs of genetic testing (http://www.ncbi.nlm.nih.gov/projects/GeneTests/static/concepts/ primer/primerordertest.shtml#choosing). Scroll down to the sections called "Turn-Around Time" and "Cost.”
Will health insurance cover the costs of genetic testing?
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 interested in submitting the costs of testing may wish to contact his or her insurance company beforehand to ask about coverage.
Some people may choose not to use their insurance to pay for testing because the results of a genetic test can affect a person's health insurance coverage. Instead, they may opt to pay out-of-pocket for the test. People considering genetic testing may want to find out more about their state's privacy protection laws before they ask their insurance company to cover the costs. (Refer to What is genetic discrimination? (http://ghr.nlm.nih.gov/handbook/testing/discrimination) for more information.)
For more information about insurance coverage of genetic testing:
The U.S. Department of Energy Office of Science provides a brief discussion of insurance coverage for genetic testing (http://www.ornl.gov/sci/techresources/ Human_Genome/medicine/genetest.shtml#insurance).
What are the benefits of genetic testing?
Genetic testing has potential benefits whether the results are positive or negative for a gene mutation. Test results can provide a sense of relief from uncertainty and help people make informed decisions about managing their health care. For example, a negative result can eliminate the need for unnecessary checkups and screening tests in some cases. A positive result can direct a person toward available prevention, monitoring, and treatment options. Some test results can also help people make decisions about having children. Newborn screening can identify genetic disorders early in life so treatment can be started as early as possible.
For more information about the benefits of genetic testing:
The National Cancer Institute provides a brief discussion of the benefits of genetic testing (http://www.cancer.gov/cancertopics/understandingcancer/genetesting/ page29).
Additional information on this topic is available in the fact sheet Gene Testing (http://www.ornl.gov/sci/techresources/Human_Genome/medicine/genetest.shtml# procon) from the U.S. Department of Energy Office of Science.