Your genetic test results may change – here's why

The first wave of routine genetic testing has already helped millions of people know their inherited risk for certain diseases such as cancer. But a new study released Tuesday JAMA suggests that as our knowledge of genetics develops, these early results sometimes need to be revised.

Researchers at the University of Texas Southwestern Medical Center have decided to examine the results of more than 1.5 million genetic tests administered to 1.45 million people in a single laboratory since 2006. The tests aimed to identify the genetic risk of patients being women.

From 2006 to 2018, they found that nearly 60,000 modified reports had to be published because a single genetic variant identified in the original outcome had been reclassified as probably harmless or potentially risky after the test. In total, approximately 6.4% of the 45,000 unique variants found in these tests (from 2006 to 2016) have been reclassified.

Most of these revisions did not come from genetic variants identified as benign or risky. For example, only 0.2% of the genes at risk or likely to be at risk have been downgraded. Most of the revisions came from genetic variations whose meaning we simply did not know. Approximately 25% of the unknown variants identified in these tests (184,327 in total) were reclassified.

"If a variant is reclassified as pathogenic, then it is important for the patient," said in a statement the senior author Theo Ross, an oncology geneticist and professor of internal medicine at the university.

People with newly identified mutations for Lynch Syndrome, a genetic condition that increases the likelihood of multiple cancers, including colon cancer, skin and brain, require more screening tests and even in the case of benign mutations newly identified, modified results can bring peace of mind.

Overall, over 90% of the unknown mutations in the study have been reclassified as benign, while just under 8% have been reclassified as risky or likely to pose a risk. However, despite the good news, the team's findings highlight the speed with which new research can change our understanding of genetic risk. In the study, they noted, it took less than two years for the modified reports to be returned to patients.

"The implications of this study are threefold," she said. "Physicians need to be aware of how quickly knowledge about genetic variants is progressing and that reclassifications are commonplace. Laboratories should regularly review information on gene variants and alert physicians to changes. Finally, patients and their family members should be informed of reclassifications made by their doctor so that they can make informed choices. "