Scientists are developing a blood test that could identify people with the Type 1 diabetes earlier, maybe decades, before symptoms develop.

Type 1 diabetes, an autoimmune disease that destroys the insulin-producing cells in the pancreas, is the rarer form of diabetes that accounts for about 10 percent of cases of the disease. It is sometimes called juvenile diabetes.

Doctors currently diagnose Type 1 diabetes when patients present with symptoms, such as excessive thirst, weight loss, and blurred vision. But damage to the body begins years earlier, when the disease process begins.

In London, scientists discovered that the cells in the pancreas that produce insulin release a molecule called microRNA 375. In people with Type 1 diabetes, microRNA 375 is released into the bloodstream in large quantities as soon as the cells begin to die, which could make it a useful biological marker for diagnosing the disease, researchers said.

They now plan to study whether the marker can be used to reliably predict who will develop diabetes and, if so, at what stage treatment should begin.