This week, the Food and Drug Administration told 23andMe, purveyor of personal genetic tests that promise consumers insight into their health, to stop selling its $99 genetic testing kits. In addition to doubting the tests’ accuracy, the FDA is concerned that consumers provided with inaccurate health information will decide to undergo unnecessary medical procedures or modulate their medication without a physician’s supervision.
Consumers with a sense of curiosity can have their fun as long as they don’t lose their heads, say scientists at Fred Hutchinson Cancer Research Center.
“I’m not surprised” by the FDA’s concerns, says Dr. William Grady, a gastroenterologist and cancer geneticist at Fred Hutch who cares for patients with hereditary cancer syndromes as the medical director of the Gastrointestinal Cancer Prevention Program at the Seattle Cancer Care Alliance. Grady’s research focuses on identifying genetic biomarkers that distinguish cancerous and pre-cancerous cells from healthy colon tissue, prompting him to approach genome-wide personal genetic screens with caution. He notes that it will take rigorous testing to demonstrate the tests' accuracy in reporting disease risks.
23andMe draws from studies linking specific genetic variants with increased disease risk, but such reports need to be meticulously validated before being used in any diagnostic capacity, cautions Grady. In such epidemiological studies, “the false positive rate is very high,” he explains, noting that less than one percent of such reports are validated in further tests.
Also, the way genetic variants influence disease risk across different populations of people is poorly understood — making the disease risk of a genetic variant in any individual more difficult to evaluate, said Grady.
'We’re dealing with shades of gray'
A recent study comparing results among three personal genetic testing companies, including 23andMe, reported that of the genetic variants surveyed for 22 diseases, only 7.1 percent were covered by all three companies. Even if the tests were extraordinarily accurate, this gives only a tiny window onto a patient’s disease risk.
Grady cautions that people who choose to take personal genetic tests shouldn’t take them too seriously. A few variants that increase cardiac disease risk don’t guarantee death by heart attack, and lacking all known risk variants doesn’t absolve anyone from taking steps to maintain their health. Most importantly, Grady notes, it’s still not always clear how genes and environment combine to affect disease risk. Although some genetic variants strongly influence disease risk, others are more swayed by environmental factors, explains Dr. Ulrike Peters, a cancer epidemiologist in the Public Health Sciences Division at Fred Hutch.
Peters cautions that some people “may not be completely aware of what they’re getting into,” and fears that such tests could cause stress or lead to more frequent but unnecessary screenings or more invasive surgical interventions. It’s important for companies providing personal genetic screens to communicate their findings in a clear and understandable way, she says. Peters considers such tests “a piece of the future,” but would prefer to see them utilized in a more medical setting, where patients could receive counseling with their results.
In Grady’s practice, patients often struggle to understand their disease risks when confronted with a few different genetic variants that affect colon cancer risk in different ways. It’s important to realize “these are just probabilities,” he says. “Most people want very black and white answers to medical questions, but we’re dealing with shades of gray here. Genetics is one part of a complex combination of factors that influence whether an individual is likely to get a specific disease and that will influence the severity of the disease.”
23andMe’s value lies more as “entertainment genetics,” says Dr. Chris Carlson, a geneticist in Fred Hutch’s Public Health Sciences Division. A personal genetic test will probably give more useful information about a person’s ancestry than their health, he explains. “As geneticists, we want people to be excited about genetics, but most people could get more information about their health risks by looking at their family tree.”
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