Clinicians may be able to identify patients at the highest risk of developing type 1 diabetes with a simple saliva test.
For many children with type 1 diabetes, a diagnosis only comes after they find themselves hospitalized in life-threatening diabetic ketoacidosis. Researchers in Virginia hope to change that.
Scientists at the Center for Public Health Genomics at the University of Virginia in Charlottesville have developed a test that they think may be able to predict the risk of type 1 diabetes.
Testing has been difficult because there is no single gene responsible for type 1 diabetes. Stephen Rich, PhD, FAHA, director of the Center for Public Health Genomics, says the new test combines the numerous gene variants that play a role in type 1 diabetes and may predict as many as 90% of cases.
Type 1 diabetes affects up to 1 in 300 children, and occurs when the autoimmune system destroys the insulin-producing beta cells in the pancreas. The risk of type 1 diabetes is half genetic and half environmental, according to another paper Rich published in Current Opinion in Endocrinology, Diabetes and Obesity on the role of genetics in type 1 diabetes, but advances in genomic mapping have provided a wealth of data that can be used to predict risk and possibly evaluate treatment efficacy.
“The test for ‘high genetic risk’ of type 1 diabetes is based upon extensive prior research that has identified 80% to 90% of the genetic risk-that accounts for about one-half of the total risk-for type 1 diabetes,” Rich says.
Testing is done with a saliva sample which is then checked against 82 genetic sites. A cutoff is used to identify subjects with a 10-fold increased risk of developing type 1 diabetes, he says.
“For those at high genetic risk, we then offer autoantibody screening-4 islet autoantibodies that are biomarkers of potential development of type 1 diabetes,” Rich says. “If a participant has 2 or more of the 4 autoantibodies, then we feel that careful monitoring is suggested to determine potential disease progression.”
The cost of the genetic test is only $7, and Rich says at-risk children and teenagers-perhaps those with a family history of the disease-and those deemed at the highest risk can then be tested periodically for the antibodies that signal active disease. The antibody test costs about $75, but the genetic test can weed out lower risk individuals and perhaps avoid additional unnecessary, expensive antibody testing. According to 1 paper of genetic testing in type 1 diabetes, Rich states that children with lower genetic risk would also be evaluated for environmental factors that might contribute to development of the lifelong autoimmune disease. In the future, the data collected from these genetic tests could also be used to investigate what types of treatments work best on different gene variants, according to the report.
The test is not perfect, but it’s a start, Rich says.
“Not everyone with a high genetic risk will develop type 1 diabetes, and those without a high genetic risk can still develop the disease; thus, we provide signs and symptoms to everyone to increase knowledge of how it presents,” Rich says. “Currently, there is no treatment to prevent type 1 diabetes, yet knowing who may be developing the disease will allow the prevention of diabetic ketoacidosis.”
The test is still in the research stage, and Rich says it isn’t clear yet if the test would be beneficial to use as a screening tool for the general population.
“The general population risk of type 1 diabetes is about 4 out of 1000, and those with a positive genetic test now have a risk of about 4 out of 100. Whereas other diseases have a strong family history, the vast majority of those who develop type 1 diabetes-more than 90% of cases-have no family history,” Rich says. “So it is important to be able to detect those at high risk, because so many cases have no family history. It should be noted that the risk of type 1 diabetes if there is a parent or sibling affected is much higher-about 8%-than the positive genetic test, so the test could be used to determine if a child with a positive family history has a ‘not high’ genetic risk, although autoantibody testing is likely to be useful in any situation with a positive family history.”
Although there is still much work to be done, Rich says he hopes the test could be used to identify risk and direct future research on treating the disease.
“Our hope is that the test can be a first-line indication of who would be at high genetic risk of type 1 diabetes-or better define an individual’s genetic risk-that could lead to targeted immune testing. Although there is only the autoantibody test that predicts ‘stage’ of risk, research is ongoing by many groups that can identify more and better biomarkers,” Rich says. “As we know more about the development of type 1 diabetes from multiple sources, the genetics is a one-time test, and can form the baseline of all subsequent tests for improved prediction, prevention and discovery of new therapeutics.”