Study Finds HbA1c Testing Could Improve Youth Diabetes Screening

Elizabeth Selvin, PhD, MPH

A new study from Johns Hopkins Bloomberg School of Public Health is shedding light on the clinical usefulness of hemoglobin A1c (HbA1c) testing as a screening tool for type 2 diabetes in youth populations.

Results of the study indicate expanding HbA1c could offer greater insight into future risk of diabetes and cardiovascular disease, leading investigators to suggest HbA1c testing should be used more frequently as a screening tool in real-world settings.

"Our study demonstrates that HbA1c is a useful non-fasting test for identifying high-risk youth who could benefit from lifestyle interventions to prevent diabetes and cardiovascular disease later in life," said lead investigator Elizabeth Selvin, PhD, MPH, a professor of epidemiology at Bloomberg School's Department of Epidemiology, in a statement.

While the prevalence of type 2 diabetes continues to rise among US populations, current screening criteria result in many instances of diabetes and prediabetes going undiagnosed. In an effort to improve screening and diagnosis, Selvin and colleagues from Johns Hopkins designed the current study to identify a more optimal approach to diagnosis of prediabetes and diabetes in youth populations.

Using data from the U.S. National Health and Nutrition Examination Surveys (NHANES) conducted from 1996-2016, investigators designed their study with 2 specific aims. The first was to examine the performance of American Diabetes Association (ADA) risk-based screening criteria. The second aim to evaluate performance of definitions of prediabetes and diabetes based on hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), either HbA1c or FPG, or both HbA1c and FPG (confirmatory definition) to identify youth at high cardiometabolic risk.

From the database, investigators identified a cohort of 14,119 subjects aged 10-19 years for inclusion in their study. Upon analysis, investigators found 25.5% of youth in the US were eligible for screening under the ADA’s 2018 screening criteria compared to just 10.6 million under the 2016 criteria.

Additionally, results indicated sensitivity and specificity of the screening criteria for detecting any hyperglycemia were low for both HbA1 at 5.7% or greater (sensitivity, 55.5%; specificity, 76.3%) and FPG at 100 mg/dL or greater (sensitivity, 35.8%; specificity, 77.1%). For confirmed undiagnosed diabetes was rare, which was defined by an HbA1c of 6.5% or greater or FPG of 126 mg/dL or greater, with rates among youth less than 0.5%.

Investigators pointed instances of undiagnosed diabetes were rare, with screening identifying more than 85% of total diabetes.

When assessing associations with cardiometabolic risk, results suggests associations were consistently stronger and more specific for HbA1c-defined hyperglycemia (specificity, 98.6%; sensitivity, 4.0%) than FPG-defined hyperglycemia (specificity, 90.1%; sensitivity, 19.4%)

"Some pediatricians have already been using HbA1c, but there hasn't been sufficient guidance from pediatric organizations," Selvin added in the aforementioned release. "I'm hoping that these results will help inform and guide the use of this important screening tool in clinical practice."

This study, “Screening and Diagnosis of Prediabetes and Diabetes in US Children and Adolescents” Was published in Pediatrics.