An Experimental Genetic Test Gives Early Warning For Kids At Risk Of Type 1 Diabetes

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Nearly half of all children who develop Type 1 diabetes don't know they have the disease until they end up in the hospital with a condition that puts them at risk of coma or even death.

Researchers in Virginia have set out to see if a genetic test for Type 1 diabetes can eliminate many of those emergencies.

"The risk of Type 1 diabetes is about half genetic and half unknown," says Stephen Rich, director of the Center for Public Health Genomics at the University of Virginia. His team developed a test that can identify people who carry that genetic susceptibility.

Unlike most genetic conditions, there's no single gene responsible for Type 1 diabetes risk. Over the years, scientists have identified dozens of gene variations that each contribute a small amount. The test developed at U.Va. looks at all those variants and explains about 90% of the known genetic risk.

"In a complex disease like Type 1 diabetes, we're probably unique in that we understand the vast majority of the genetic risk," he says. In comparison, most tests that identify multiple gene variants linked to a disease or trait explain only a smaller fraction of the genetic component – and as a result they are far less useful.

So what can people do with this information? Outright prevention of Type 1 diabetes isn't possible. Type 1 diabetes is an autoimmune disease, which is driven by certain antibodies that circulate in the blood. There's no simple advice to avoid it – you can't adjust your diet or exercise more.

But it is possible to identify children before they develop serious complications.

So Rich's strategy is simple: use the genetic test to find people at highest risk (at the cost of about $7 per test) and then give them periodic blood tests to look for the troubling antibodies. The antibody test costs about $75, and needs to be repeated regularly, which is why a one-time genetic test to identify those at higher risk makes sense as a first step.

About 40% of kids who develop Type 1 diabetes don't know it until they develop a serious condition called diabetic ketoacidosis. Untreated, children with this condition can end up in a coma or can even die. "We can prevent that by monitoring them carefully," Rich says.

Rich and his colleagues have so far recruited about 2,000 children for the study. Researchers hang out in the waiting rooms of a variety of health clinics and pediatrics practices to enroll a diverse group of kids. With parental permission, the youngsters donate a saliva sample, which gets sent out to a lab for DNA analysis.

Of the roughly 2,000 kids tested to date, about 60 carry the higher genetic risk.

Charlottesville resident Jeri Seidman says her 12-year-old daughter Hannah is one of them. "It was kind of stunning to me," Seidman says.

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The genetic test indicates that a child is at 10 times the risk of developing Type 1 diabetes. That may sound like a lot, but here's another way frame it. The risk goes from 4 in 1,000 (0.4%) to 4 in 100 (4%), so developing the condition is still fairly unlikely. Even so, Seidman says that still gives her valuable information.

"I have a lot of friends who have kids with Type 1," she says, "and living with Type 1 is fine." What she worries about is the condition's sudden onset. "My friends' children have been hospitalized for many days, and the initial diagnosis was incredibly scary."

If Hannah develops diabetes, she will probably avoid the emergency room, because doctors can now monitor her antibodies with periodic blood tests, and have advance warning if the disease starts to appear.

The hospital at the University of Virginia sees seven to 10 new cases of Type 1 diabetes a month, says Dr. David Repaske, the head of pediatric endocrinology. Parents often just think their child has a prolonged case of the flu, since the symptoms are similar. Many of these kids aren't diagnosed until they are hospitalized.

But sometimes parents who have had one child with Type 1 diabetes will recognize those same symptoms early on in a sibling and take action. "It's a much better course of initiating therapy," he says. "They stay out of the ICU. They even stay out of the hospital, in most cases."

This testing may not make sense strictly from a dollars-and-cents point of view, according to a study from the University of Florida, published in 2015. Rich says the leading advocacy group, JDRF, is currently running its own cost/benefit analysis.

If the University of Virginia team can demonstrate the value of genetic screening in its current research, the next step would be to apply it across the state.

Repaske has even bigger hopes.

"We have the potential to include this on the newborn screen that every child in the country participates in," Repaske says. "But then there's the ethical dilemma: How are people going to deal with this information?"

The panel of routine screening tests for newborns provides yes-or-no answers for a variety of inherited diseases, not a probability, as the diabetes test does.

Most kids with positive Type 1 diabetes results won't get Type 1 diabetes, and half the kids who do will not have been flagged by a genetic test, since there are nongenetic risk factors.

U.Va. pediatrician Julia Taylor says it's a challenge to explain all this to parents. "It is a lot of uncertainty that you're trying to communicate," Dr. Taylor says, "and the risk is not easy to grasp unless you're a numbers person or a statistician, which I'm not!"

The ethical guidelines around genetic testing generally find that parents should have the opportunity to access information — provided they can do something with it.

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"Being told your child's at increased risk for something and there's nothing you can do about it can be very overwhelming, or give you some anxiety," says Kitty Keating, a genetic counselor at U.Va. "But knowing that there is something we can do to monitor it, even if their child is likely to never develop it, I think gives parents some relief, or a little bit more control."

You can contact NPR Science Correspondent Richard Harris at rharris@npr.org.