Predictive Genetic Testing: What It Is and How It Works

Predictive genetic testing analyzes a person’s DNA for specific gene mutations. It is performed on healthy individuals to identify inherited variants that could elevate the risk of developing a health condition later in life. This type of testing does not diagnose an existing illness but provides information about a potential future health issue. The results can empower people to make informed decisions about their medical care and lifestyle long before symptoms appear.

Purpose and Types of Predictive Testing

The purpose of predictive testing is to provide information that can guide future medical and lifestyle choices, especially for those with a family history of a genetic condition. This knowledge allows for proactive health management, such as more frequent screenings. The implications of the results differ based on the two main types of predictive tests.

One category is presymptomatic testing. This is used when a specific gene mutation is known to cause a disorder, and its presence means the individual will, with near certainty, develop the condition if they live long enough. An example is Huntington’s disease, a progressive brain disorder. A positive presymptomatic test for the Huntington gene indicates that the person will eventually develop the disease.

A more common category is predispositional testing. This test searches for gene mutations that increase a person’s risk of developing a disorder, but it does not guarantee they will. Examples include mutations in the BRCA1 and BRCA2 genes, which significantly raise the lifetime risk of hereditary breast and ovarian cancer. Other examples include testing for mutations associated with Lynch syndrome or variants linked to a higher likelihood of developing Alzheimer’s disease.

The Genetic Testing Process

The process often begins with a consultation with a genetic counselor, especially if there is a known family health history. This healthcare professional evaluates the patient’s family medical history and explains the science behind the test. They also discuss the potential benefits, drawbacks, and limitations of learning this genetic information.

Following counseling, the patient must provide informed consent. This is a formal acknowledgment that they understand the test’s purpose, the nature of the possible outcomes, and the psychological and medical implications. This step ensures the decision to test is made with full awareness of the potential consequences for the individual and their family.

Once consent is given, a biological sample is collected from the patient, most commonly blood drawn from a vein or a saliva sample collected in a tube. This procedure is simple and carries minimal physical risk. The sample is then carefully labeled and sent to a specialized laboratory for analysis.

At the laboratory, technicians perform the genetic analysis. They focus specifically on the gene or genes in question, looking for particular mutations identified as risk factors. The analysis targets relevant sections of DNA, making the process efficient and focused on the clinical question.

Understanding Your Test Results

After the analysis is complete, the results are sent to the healthcare provider or genetic counselor, who discusses them with the patient. Interpreting these results requires careful explanation. The counselor helps translate the technical lab report into meaningful information the patient can act upon.

A positive result indicates the specific gene mutation was found. For a presymptomatic test, this means the individual will develop the disorder. For a predispositional test, such as for a BRCA1 mutation, it means the person has a significantly increased risk of developing associated cancers.

A negative result means the specific gene variant was not detected. This does not mean the person has zero risk of developing the disease. It simply means their risk is not elevated due to that particular inherited mutation, and their risk level may be similar to that of the general population.

Sometimes, a test yields a Variant of Uncertain Significance (VUS). This result means a gene change was identified, but there is not enough scientific evidence to know if it is harmless or increases disease risk. A VUS is not a positive result and does not prompt the same medical actions, creating a state of uncertainty while researchers study the variant.

Navigating Life After Testing

For those with a positive predispositional test result, medical management becomes the focus. This might involve increased surveillance, such as more frequent mammograms or colonoscopies, to detect disease early. In some cases, preventative medications or risk-reducing surgeries may be considered.

The emotional impact of testing can be significant regardless of the outcome. A positive result may cause anxiety or fear, while a negative result can lead to relief or even “survivor guilt” if other family members tested positive. The uncertainty of a VUS result can also be a source of stress.

Communicating results to family is another consideration. Since genetic mutations are inherited, a positive result has implications for relatives who may share the same risk. Deciding how and when to share this information can be a complex process, and genetic counselors can provide guidance.

A concern for individuals is the potential for genetic discrimination. In the United States, the Genetic Information Nondiscrimination Act (GINA) provides protections. GINA makes it illegal for health insurers to use genetic information to determine eligibility or costs. It also prevents employers from using this information in hiring, firing, or promotion decisions.