Combo of Tests Predicts Type 1 Diabetes

Eighty percent accuracy found, could enhance future clinical trials

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By E.J. Mundell
HealthDay Reporter

THURSDAY, Oct. 27, 2005 (HealthDay News) -- A combination of tests can accurately predict who will develop the inherited, type 1 form of diabetes, researchers announced Thursday.

The good news, however, is only applicable to future clinical trials and not for individuals hoping to avoid an inherited risk. And it comes amid a gloomier prognosis for the more prevalent, obesity-linked type 2 diabetes.

"If we want to prevent type 1 diabetes, we need to know in whom to prevent it," explained senior researcher Dr. Dorothy Becker, chief of the division of pediatric endocrinology and diabetes at Children's Hospital of Pittsburgh.

Trials into the prevention of type 1 diabetes -- which affects about 5 percent of all diabetics -- have been stymied because researchers have lacked a reliable means of pinpointing individuals who are healthy now but at high risk of developing the disease later on, she added.

"If you're going to test a drug or something like immunosuppression -- which have potential side effects -- you're not going to risk those side effects unless somebody is really going to get the disease," she explained at a special American Medical Association diabetes briefing held Thursday in New York City. "That's why we want to know who's going to get it, and when."

Type 1 diabetes "is probably an autoimmune disease: For whatever reason, the body's immune system turns around and recognizes [pancreatic] insulin-producing cells as 'not mine,' or foreign, and sets up a destructive process," Dr. Frank Vinicor, director of the division of diabetes translation at the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta, told reporters.

However, trials focused on prevention would need to collect individuals known to be at high risk for type 1 disease, which includes 5 percent to 6 percent of the children of type 1 diabetics.

And current individual tests to pinpoint who they may be are not accurate enough. One screen, called the "islet cell antibody," can only predict the risk with about 50 percent accuracy, Becker said, and it is cumbersome and expensive. Two more recently developed tests -- relying on diabetic 'biomarkers' called GAD65 and IA-2 -- are cheaper and easier but are still relatively inaccurate.

In their study, Becker and colleague Dr. Massimo Pietropaolo tracked the long-term health histories of almost 1,500 first-degree relatives of type 1 diabetics. They wanted to see if a combination of the three tests might work to predict the long-term odds of developing the disease.

"Our work was pretty unique because it's been going on since 1979, so we have 22 years of follow-up," Becker said.

The team found that the islet cell antibody test plus the two biomarker tests predicted with 80 percent accuracy who would go on to develop the disease.

The finding should provide a big boost to researchers around the world looking to design clinical trials aimed at preventing the disease, Becker said. "We're trying to work out how these trials should be designed, and unless we select people accurately, we'll never know," she said.

As an unexpected bonus, Becker and Pietropaolo's work also uncovered a "mystery protein" in islet cells that might play a role in promoting a much more aggressive form of type 1 diabetes.

"The islet cell antibody test was picking up something else that seems to be important to the rate of progression," Becker said, adding that Pietropaolo's lab is now working to identify that protein.

In the meantime, Becker said her group is seeking healthy children of type 1 diabetics to volunteer for new trials aimed at preventing the disease. Her team will screen the volunteers with the combination tests and include those at high risk in the trials. Interested individuals can find out more at www.trigrnorthamerica.org.

While the discovery, to be published in the December issue of Pediatric Diabetes, is good news for the fight against type 1 diabetes, the news for those with obesity-linked type 2 disease was less uplifting.

The prevalence of type 2 diabetes in the United States "is bad, it's been getting bad, and it's going to get worse before it gets better," said Vinicor.

In fact, new CDC figures released Wednesday showed that almost 21 million Americans have now been diagnosed with diabetes -- up 14 percent from numbers released just two years ago.

In type 2 diabetes, rising obesity causes the body's cells to become less sensitive to insulin, which is secreted by the pancreas. This can lead to dangerously unstable blood sugar levels, which in turn have been linked to heightened cardiovascular risks and other serious conditions.

According to Vinicor, if current trends continue unchanged, individuals born in the year 2000 will have a 1-in-3 chance of developing diabetes at some point in their lives. He also noted that 29 percent of Americans who are living with type 2 diabetes today don't know they have it.

And each day, Vinicor added, the disease takes it toll: Every 24 hours, 4,100 new cases will be diagnosed in the United States, 810 people will die from the disease, 230 diabetics will undergo diabetes-linked amputations, 120 new patients will require kidney dialysis or transplant, and 55 will go blind from the disease.

More information

For much more on diabetes, head to the American Diabetes Association.

SOURCES: Dorothy Becker, M.D., professor, pediatrics, University of Pittsburgh, and chief, division of pediatric endocrinology and diabetes, Children's Hospital of Pittsburgh; Frank Vinicor, M.D., M.P.H., director, division of diabetes translation, U.S. Centers for Disease Control and Prevention, Atlanta; December 2005, Pediatric Diabetes; Oct. 27, 2005, news briefing, American Medical Association, New York City

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