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Researchers conducted a cross-sectional analysis of more than 14,000 youth in the United States and found that few meet diagnostic criteria for diabetes. Nevertheless, HbA1c is still an effective screening tool for type 2 diabetes, regardless of screening eligibility. “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 study senior author Elizabeth Selvin, PhD, MPH, professor in the Johns Hopkins’ Bloomberg School's Department of Epidemiology in a news release.
The American Diabetes Association (ADA) estimates that 34 million or 10% of Americans have diabetes, with many cases going undetected. ADA and the American Academy of Pediatrics recommend screening for type 2 diabetes and prediabetes in asymptomatic youth, in wake of rising cases of this disease in children and adolescents. Previously, this recommendation had only applied to high-risk youth that had two or more of these risk factors: non-white race, family history of type 2 diabetes, maternal gestational diabetes, or signs of insulin resistance. In 2018, ADA revised the guidance to include all overweight youth with one or more risk factors.
“The implications of this change are uncharacterized; it is unknown how many U.S. children and adolescents are eligible for screening by these new guidelines,” wrote the investigators, who published their findings in Pediatrics. To find the best approach for screening and diagnosing young people, they analyzed the data of 14,119 youth aged 10 to 19 from U.S. National Health and Nutrition Examination Surveys (1999 to 2016).
Based on NHANES blood test data for hyperglycemia, investigators determined screening eligibility using the following criteria:
- Non-white race and ethnicity.
- The participant self-reported that a health professional said he or she had a medical or family history that put them at increased risk for diabetes.
- Hypertension defined as systolic or diastolic blood pressure ≥95th percentile for age, sex, and height [ages 10–12] or systolic blood pressure ≥130 mm Hg or diastolic blood pressure ≥80 mm Hg [ages 13–19]) or dyslipidemia (total cholesterol ≥200 mg/dL, LDL-C ≥130 mg/dL, triglycerides ≥130 mg/dL, or high-density lipoprotein cholesterol [HDL-C] <40 mg/dL.
Screening eligibility applied to youths who met criteria for being overweight or obese and had one or more risk factors for diabetes. To identify youth at high cardiometabolic risk, Selvin and colleagues analyzed the performance of current prediabetes and diabetes clinical definitions based on HbA1c, fasting plasma glucose (FPG), either HbA1c or FPG, or both HbA1c and FPG.
About 25% of U.S. children and adolescents or 10.6 million were eligible for screening under the 2018 criteria. Undiagnosed diabetes was rare, only in 0.5% of the individuals studied. Most cases of diabetes received a diagnosis. As for the tests, HbA1c and FPG scored low on sensitivity and specificity for detecting hyperglycemia under the screening criteria. However, the investigators found stronger and more consistent associations between HbA1c-defined hyperglycemia and cardiometabolic risk (obesity, metabolic syndrome, and hypercholesterolemia) than FPG-defined hyperglycemia.
Odds ratios for HbA1c-defined hyperglycemia ranged from 2.6 to 4.1, compared with 1.5 to 3.0 for FPG-defined hyperglycemia. “The prevalence of obesity and abdominal obesity were higher in youth with HbA1c-defined hyperglycemia than in youth with FPG-defined hyperglycemia,” noted Selvin and colleagues.
The researchers concluded that HbA1c would be an efficient way to identify and intervene with those at high-risk. Revising testing guidelines might be appropriate. “Current screening criteria are not highly sensitive or specific and may miss high-risk youth who should be targeted for diabetes prevention,” they observed. “Targeted approaches to diabetes screening in certain settings may be warranted.”
Using the right test is important, but so are education and prevention measures, another expert stressed.
“Although more effective algorithms to determine who should have laboratory testing could be useful, for youth with obesity and multiple risk factors for developing type 2 diabetes, the principal challenge is how to effectively prevent or delay this disease for them and future generations,” wrote Tamara S. Hannon, MD in a related editorial. Simple tests such as HbA1c are important to screen for disease, but pediatricians should also employ early intervention measures. These include educating patients about prediabetes and supporting policies to help prevent disease and identify it earlier, according to Hannon, a professor of pediatrics at Indiana University School of Medicine.