Genetic testing can give several possible results: positive, negative, true negative, uninformative negative, variant of uncertain significance, or benign (harmless) variant.

Positive result. A positive test result means that the laboratory found a genetic variant that is associated with an inherited cancer susceptibility syndrome. A positive result may:

Also, people who have a positive test result that indicates that they have an increased risk of developing cancer in the future may be able to take steps to lower their risk of developing cancer or to find cancer earlier, including:

Negative result. A negative test result means that the laboratory did not find the specific variant that the test was designed to detect. This result is most useful when a specific disease-causing variant is known to be present in a family. In such a case, a negative result can show that the tested family member has not inherited the variant that is present in their family and that this person therefore does not have the inherited cancer susceptibility syndrome tested for. Such a test result is called a true negative. A true negative result does not mean that there is no cancer risk, but rather that the risk is probably the same as the cancer risk in the general population.

When a person has a strong family history of cancer but the family has not been found to have a known variant associated with a hereditary cancer syndrome, a negative test result is classified as an uninformative negative (that is, it typically does not provide useful information).

In the case of a negative test result, it is important that the persons doctors and genetic counselors ensure that that person is receiving appropriate cancer screening based on that persons personal and family history and any other risk factors they may have. Even when the genetic testing is negative, some individuals may still benefit from increased cancer surveillance.

Variant of uncertain significance. If genetic testing shows a change that has not been previously associated with cancer, the persons test result may report a variant of uncertain significance, or VUS. This result may be interpreted as uncertain, which is to say that the information does not help to clarify their risk and is typically not considered in making health care decisions.

Some gene variants may be reclassified as researchers learn more about variants linked to cancer. Most often, variants that were initially classified as variants of uncertain significance are reclassified as being benign (not clinically important), but sometimes a VUS may eventually be found to be associated with increased risks for cancer. Therefore, it is important for the person who is tested to keep in touch with the provider who performed thegenetic testing to ensure that they receiveupdates if any new information on thevariant is learned.

Benign variant. If the test reveals a genetic change that is common in the general population among people without cancer, the change is called a benign variant. Everyone has commonly occurring benign variants that are not associated with any increased risk of disease.

Genetic test results are based on the best scientific information available at the time of the testing. While unfortunately no testing can be 100% error free, most genetic testing is quite accurate. However, it is very important to have thegenetic testing orderedby a provider knowledgeable in cancer genetics who can choose a reputable testing lab to ensure the most accurate test results possible.

Excerpt from:
Genetic Testing Fact Sheet - NCI - National Cancer Institute

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