By Bob Saunders
NEW YORK (Reuters Health) May 04 - Hemoglobin A1c (A1C) levels are not sensitive or specific enough to be used to identify children and adolescents with or at risk for diabetes, according to a report in Diabetes Care online April 22.
"Our results suggest that, although A1C could be used as a clinical tool to identify type 2 diabetes, along with fasting and 2-h glucose, the use of A1C alone to pinpoint prediabetes and type 2 diabetes is not recommended," stated Dr. Sonia Caprio in an email to Reuters Health.
She and her colleagues explain that the American Diabetes Association has recommended the use of A1C to diagnose diabetes and prediabetes, based on studies in adults. With the increase in childhood obesity it has become critical to identify those conditions in young individuals, but little is known about the use of A1C for screening the pediatric population.
Dr. Caprio, at Yale University School of Medicine in New Haven, Connecticut, and colleagues therefore studied that strategy in a multiethnic group of 1156 obese children and adolescents. All the subjects underwent an oral glucose tolerance test (OGTT) and measurement of their A1C.
Based on an A1C <5.7%, 77.2% were classified as normal; 21.4% with an A1C of 5.7-6.4% were considered at risk for diabetes; and 1.4% with A1C levels >6.5% were given a diagnosis of diabetes.
However, there was poor agreement between A1C and OGTT criteria in classifying subjects.
Based on the OGTT result, 27% of those in the normal A1C category had prediabetes, according to the report. On the other hand, only 47% of those in the at-risk A1C group actually had OGTT values indicating prediabetes or diabetes. In the highest A1C strata, 12.5% had a normal glucose tolerance test, 24% had prediabetes and 62% did have type 2 diabetes.
The researchers calculated that the best A1C level for identifying prediabetes was 5.5%, but this had only a specificity of 59.9% and sensitivity of 57.0%. The optimal A1C threshold for identifying type 2 diabetes was 5.8%, yielding a specificity and sensitivity of 87.6% and 67.7%, respectively.
"Given the low sensitivity and specificity, the use of A1C by itself represents a poor diagnostic tool for prediabetes and type 2 diabetes in obese children and adolescents," Dr. Caprio and colleagues conclude.
"Our data are in agreement with those who reported using the National Health and Nutrition Examination Survey of 14,611 individuals aged 20 years, clearly showing that an A1C of 6.5% has a lower capacity to detect prediabetes and undiagnosed type 2 diabetes than the OGTT," added Dr. Caprio.
Asked if all obese youngsters should therefore be screened with an OGTT, she replied, "The OGTT should be performed in those obese children/adolescents with a strong family history of diabetes or gestational diabetes, signs of insulin resistance such as acanthosis nigricans, elevated triglycerides and fatty liver disease."
The authors of the report call for prospective studies to look at the utility of A1C measurements in children and adolescents for predicting diabetes-related comorbidities later in life.
Diabetes Care 2011.
Reuters Health Information © 2011
Cite this: A1C Not Reliable for Diabetes Screening in Pediatric Population - Medscape - May 04, 2011.