美国国家公共电台 NPR Researchers Try A Genetic Diabetes Test To Prevent Emergency Hospitalizations（在线收听）

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Almost half of all children who develop Type 1 diabetes do not learn they even have the disease until they end up in the hospital. Researchers are exploring whether a genetic test can eliminate a lot of these emergencies, which is tricky because the test raises a lot of false alarms and misses a lot of cases. NPR science correspondent Richard Harris visited a research team in Charlottesville, Va., where they are trying out the test.

RICHARD HARRIS, BYLINE: Sharon Twitty and her daughter Tierra are in the sun-filled waiting room of a health clinic at the University of Virginia when a man with a computer tablet politely approaches.

JORGE GONZALEZ: Good morning. So my name is Jorge Gonzalez I'm a clinical research study coordinator here at UVA, and we're conducting a genetic risk study for Type 1 diabetes.

HARRIS: Gonzalez explains that the study is recruiting kids to identify those at elevated risk for this condition. Sharon and her daughter quickly agree to take part.

GONZALEZ: Great. So if you can follow me. We're going to go to the very first room.

SHARON TWITTY: OK.

HARRIS: They head back behind the nursing station.

GONZALEZ: Are you familiar with consent forms?

S TWITTY: Yes.

HARRIS: Paperwork quickly out of the way, it's now 16-year-old Tierra's turn to provide a saliva sample for the study.

GONZALEZ: It helps to make a fishy face, like this. Bring the saliva right down to the middle.

TIERRA TWITTY: I have a gun in my mouth.

S TWITTY: Take it out.

HARRIS: Out it comes. Tierra is game to give a spit sample, but she says her mouth is too dry.

UNIDENTIFIED PERSON #1: Give it your best shot, girl.

GONZALEZ: You're doing great.

HARRIS: Gonzalez ultimately collects the spit on cotton swabs. It's all over in a few minutes.

UNIDENTIFIED PERSON #2: All right, you've done your bit for science. Congratulations.

(LAUGHTER)

HARRIS: So far, Gonzalez and his colleagues working in other clinics have collected about 2,000 spit samples. Those go to a lab where DNA is extracted for an unusual genetic test. Steve Rich, director of the UVA Center for Public Health Genomics, explains the strategy.

STEVE RICH: The risk of Type 1 diabetes is about half genetic and half unknown.

HARRIS: And unlike most genetic conditions, there's no single gene responsible for that genetic risk. Over the years, scientists have discovered dozens of gene variations that each contribute a tiny amount to the risk. The test Rich developed costs only about $7. It looks at all those variants and together explains about 90% of the genetic risk. Most genetic tests of this type do far worse.

RICH: In a complex disease like Type 1 diabetes, we're probably unique in that we actually understand the vast majority of the genetic risk.

HARRIS: The question is what to do with that information.

RICH: It's an autoimmune disease. So there is no, exercise more. There is no, stop eating sugar. There is no, have a better diet - that we know that will actually affect things.

HARRIS: But what they can do for kids who have this genetic risk is run a blood test. Before symptoms kick in, children develop antibodies in the blood. Rich says parents and doctors can then use that information to make sure the first sign of trouble isn't a scary crash in blood sugar.

RICH: And since 40% of kids who get Type 1 diabetes go into this coma, we can prevent that by monitoring them carefully.

HARRIS: Out of the 2,000 kids tested in this study, about 60 turned out to carry this higher genetic risk. Charlottesville resident Jeri Seidman says her 12-year-old daughter Hannah is one of them.

JERI SEIDMAN: It was kind of stunning to me. And I got the news in a week when she'd had some other issues. I think she fainted at school or something, and I was like, oh, my goodness.

HARRIS: 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 to frame it - the risk goes from 4 in a 1,000 to 4 in 100, a 4% risk. But Seidman says that still gives her valuable information.

SEIDMAN: I have a lot of friends who have kids with Type 1, and living with Type 1 is fine. But the development of Type 1, the initial diagnosis - my friends' children have been hospitalized for many days, and the initial diagnosis was incredibly scary.

HARRIS: If Hannah develops diabetes, she will probably avoid the emergency room because doctors can now watch her antibodies with periodic blood tests. Hannah already gets blood draws to monitor another health condition.

SEIDMAN: The only hesitation was Hannah hates to have her blood drawn. She was like, I have to get my blood taken twice? And I said, no, I made sure they would do it all at the same time. And she was like, OK, because you know I was not going to do it if I had to do it twice. And I was like, I know. I know (laughter).

HARRIS: The hospital at the University of Virginia sees seven to 10 new cases of Type 1 diabetes a month, says 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. But sometimes parents who've had one child with Type 1 diabetes will recognize those same symptoms early on in a sibling.

DAVID REPASKE: It's such a much better course of initiating therapy. And they stay out of the ICU; they even stay out of the hospital in most cases.

HARRIS: If the University of Virginia team can demonstrate the value of genetic screening in its current program, the next step will be to apply it to the entire state. Dr. Repaske has even bigger hopes.

REPASKE: We have the potential to include this screen on the newborn screen that every child in the country participates in. But then there's the ethical dilemma. So what - how are people going to deal with this information?

HARRIS: The routine screening test for newborns provides yes or no answers, not simply a probability as the diabetes test does. Most kids with positive results won't get Type 1 diabetes, and half the kids who will do not show up on this test, since there are nongenetic risk factors. UVA pediatrician Julia Taylor says it's a challenge to explain all this to parents.

JULIA TAYLOR: So it is a lot of uncertainty that you're trying to communicate. And the risk is not something that's easily grasped, I think, unless you're a numbers person or a statistician, which I'm not.

HARRIS: The ethical guidelines around genetic testing generally find that parents should at least have the opportunity to access information, provided they can also do something with it. That's been the experience of UVA genetic counselor Kitty Keating.

KITTY KEATING: Being told that your child's at increased risk for something and there's nothing you can do about it, can feel very overwhelming or give you more anxiety. But knowing that there is something we can do to monitor it, even if their child is likely to never develop it, I think that gives parents some relief or a little bit more control.

HARRIS: They'll learn more about that as their pilot test continues.

Richard Harris, NPR News.

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