The question of who should undergo genetic carrier screening was debated on Friday morning during the John and Marney Mathers Lecture “Genetic Screening for Everyone or Just a Selected Few.”
Mary E. Norton, MD, professor of obstetrics, gynecology, and reproductive sciences at the University of California, San Francisco, argued that more is not necessarily better.
“Often, it is the technology that is driving the screening. It is not that someone says we need to have a test for x, y, or z or an esoteric condition,” said Dr. Norton. Traditionally, genetic screening has been based on race and ethnicity, such as testing those of Ashkenazi Jewish decent for Tay-Sachs disease.
“Not only does it make more sense to test for things when it is more likely that you are going to find something, but generally the test is more accurate when someone is at higher risk,” said Dr. Norton.
But Lee P. Shulman, MD, who argued that extended carrier screening identifies more pregnancy risks than other modalities, noted the problems with ethnic-specific screening.
“I never have been a fan of ethnic specific screening just because the majority of people in my practice in Chicago and Memphis have no clue what their ethnicity is,” he said, adding that, in general, many people are never told their ancestry details.
Dr. Shulman, chief of clinical genetics in the Division of Obstetrics and Gynecology at Northwestern University Feinberg School of Medicine, Chicago, cited a JAMA®, the Journal of the American Medical Association study of more than 340,000 ethnically diverse patients who were evaluated comparing routine expanded carrier screening to ethnic based screening.
“Ethnic based carrier screening picked up only 55 percent of genetic conditions in the Ashkenazi populations,” he said. “That should give all of you a bit of a pause.”
Both agreed that the extended carrier screening business was much like the Wild West at the moment. For example, Dr. Norton asked, what criteria do laboratories require before including variants on a panel?
“I would say there is only one: That there is a test,” said Dr. Norton, showing a partial list of the many diseases included on extended carrier screening panels. “I’m a geneticist. I spend all day, every day doing genetics, and a large majority of these diseases, I’ve never heard of. It’s hard for me to tell a patient they need to screen for achromatopsia, for example.”
Counseling patients can be challenging, she said, noting that informed consent is vital and explaining that some of the conditions on the expanded screening panel may be mild, adult-onset, have a low detection rate, or may require partner testing that can add to the cost if the partner doesn’t have insurance.
“Whatever you ultimately choose to do, you must be blindly consistent. You don’t have different levels of care for different patients,” said Dr. Shulman. “You need to establish a standard approach that is consistently offered to and discussed with each patient.”