Author: Gina Kolata / Source: New York Times
The results of a genetic test may seem final — after all, a gene mutation is present or it is not. That mutation increases the risk of a disease, or it does not.
In fact, those findings are not as straightforward as they might seem, and the consequences may have grave implications for patients.
While a person’s genome doesn’t change, the research linking particular bits of DNA to disease is very much in flux. Geneticists and testing labs constantly receive new information that leads them to reassess genetic mutations.
As a result, a mutation seen as benign today may be found dangerous tomorrow. And vice versa. But there is no good way to get the new information to doctors and patients.
The result: The gene test you had a few years ago might yield a startlingly different result now.
The problem affects a minority of patients, mostly people with unusual mutations. The more common disease-causing mutations — like those that predispose you to breast or colon cancer — are so well studied that their meaning is not in doubt.
In a recent study, researchers at Myriad Genetics, a diagnostic company, reviewed data on 1.45 million patients who had genetic tests from 2006 to 2016 to see if the results originally reported still held true.
The lab issued new reports for nearly 60,000 of them, meaning the old results had been superseded by new data.
But many patients who carry mutations that have been reclassified remain in the dark. “The system is completely chaotic,” said Dr. Sharon E.
Plon, a clinical geneticist at Baylor College of Medicine.There is no systematic way, she said, to tell patients and doctors that a mutation once thought harmless has been shown to be a health hazard or one thought dangerous is actually benign.
“Some labs report out only one-time results,” said Dr. Theodora Ross, director of the cancer genetics program at the University of Texas Southwestern Medical Center. “They are not going back to reassess test interpretations from ten years ago unless doctors ask.”
But doctors seldom ask, she added.
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Normally, a doctor orders genetic testing for a person with a strong family history of, say, heart attacks, strokes or cancer. A sample of a patient’s blood or saliva is sent to a lab, where the patient’s DNA is scanned for unusual alterations.
Not all of these are harmful. The lab compares the mutations to those shown in scientific studies to cause disease.
Some patients are told they have a mutation that is meaningless. Others learn they have “a variation of unknown significance” in a suspect gene — meaning no one knows quite what to make of it.
Still other patients have a mutation deemed dangerous, meaning there is a very high risk of developing cancer, heart disease or another condition. For those patients, such a result can mean regular monitoring and can alter a number of life decisions, including whether to have children.
Reclassification is a particular problem for members of…
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