From the Journals

Screening criteria for diabetes in youth won’t capture all at high risk



The current risk-based criteria for screening for type 2 diabetes or prediabetes in youth have low sensitivity and specificity for detecting these disorders, and therefore “may miss high-risk youth who should be targeted for diabetes prevention,” according to the investigators of a cross-sectional analysis of youth in the 1999-2016 National Health and Nutrition Examination Survey (NHANES) database.

A health care provider prepares a patient for a blood test Belyjmishka/Getty Images

Regardless of whether or not youth meet screening eligibility, they say, hemoglobin A1c appears to be a “specific and useful test” for detecting high-risk youth.

Those with prediabetic levels of A1c or fasting plasma glucose (FPG) – A1c especially – had a high burden of other cardiometabolic risk factors that could benefit from lifestyle interventions to prevent diabetes and cardiovascular risk in adulthood, wrote Amelia S. Wallace and coinvestigators at the Johns Hopkins Bloomberg School of Public Health, Baltimore. The report is in Pediatrics.Their epidemiologic study had two aims: To assess the performance of the American Diabetes Association guidelines for screening in youth, and to evaluate how well various clinical definitions of diabetes and prediabetes identify U.S. youth at high cardiometabolic risk.

The 2018 ADA guidelines recommend screening for type 2 diabetes and prediabetes in all asymptomatic youth ages 10 years and older who are overweight or obese and who have at least one risk factor for diabetes: nonwhite race, family history of type 2 diabetes, maternal gestational diabetes, or signs of insulin resistance or conditions associated with insulin resistance (Diabetes Care. 2018:41[suppl 1:S13-S37]).

Approximately one-quarter of U.S. youth were found to be eligible for screening under the current ADA criteria, but there were few cases of confirmed diabetes (A1c greater than or equal to 6.5% and fasting plasma glucose greater than or equal to 126 mg/dL) that had gone undiagnosed (less than 0.5%), said Ms. Wallace and her associates.

Considering all hyperglycemia (undiagnosed diabetes or prediabetes) in the NHANES youth population, the sensitivity and specificity of the ADA criteria for detecting A1c-defined hyperglycemia (greater than or equal to 5.7%) were 56% and 76%, respectively, and the sensitivity and specificity for detecting FBG-defined hyperglycemia (greater than or equal to 100 mg/dL) were 36% and 77%.

The prevalence of any hyperglycemia was higher in youth who met ADA screening criteria than in those who didn’t, but there were also “a substantial number of youth with hyperglycemia in the non–screening eligible population,” they wrote. “In fact, the absolute number of youth with elevated FPG was larger in the non–screening eligible population, and the majority (88.5%) of these youth were of normal weight.”

Across all youth (irrespective of screening eligibility), both FPG and A1c-defined hyperglycemia effectively identified children and adolescents who had a high burden of cardiometabolic risk (obesity, metabolic syndrome, and hypercholesterolemia). Using a confirmatory definition of elevations in both FPG and A1c “provided the highest discrimination for cardiometabolic risk,” Ms. Wallace and her associates said.

But in comparing the single tests, risk factor associations with hyperglycemia were consistently stronger with A1c-defined hyperglycemia (odds ratios of 2.6-4.1) than FBG-defined hyperglycemia (ORs of 1.5-3.0). A1c-defined hyperglycemia “identifies a smaller, but higher-risk, population than FPG-defined hyperglycemia,” they said.

In an accompanying commentary, Tamara S. Hannon, MD, MS, of the division of pediatric endocrinology and diabetology at Indiana University in Indianapolis, said that more effective algorithms to determine who should have laboratory testing “could be useful.” Still, “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.”

Pediatricians, she said, should screen for prediabetes and type 2 diabetes “according to professional recommendations with simple clinical tests, such as A1c. Screening and education about prediabetes alone can lead to better rates of follow-up for obesity,” she noted (Pediatrics. August 2020. doi: 10.1542/peds.2020-010272).

Sheela N. Magge, MD, MSCE, who directs the division of pediatric endocrinology and diabetes at John Hopkins University, Baltimore, and was asked to comment on the study, similarly said that the findings should not discourage use of the ADA guidelines.

While the guidelines may not have optimal sensitivity and specificity, “neither HbA1c nor fasting glucose are perfect screening tools for prediabetes and likely give us different mechanistic information,” she said. (The ADA guidelines also allow the use of a 2-hour oral glucose tolerance test, but this is not often used by pediatricians, she noted.)

The measurements are “only tools used to identify children who have prediabetes and are therefore at increased risk for type 2 diabetes,” said Dr. Magge, the Lawson Wilkins Endowed Chair of Pediatric Endocrinology at the university. “These children then need to be managed and followed to try to prevent worsening glycemia.”

Both she and Dr. Hannon stressed that youth with type 2 diabetes have more rapidly progressive disease compared with adults.

Microvascular complications are seen even at diagnosis, Dr. Magge said, and “youth may face serious complications such as cardiovascular disease decades earlier than previous generations.”

Dr. Hannon also noted in her commentary that oral diabetes medications often fail in youth with type 2 diabetes, leading to insulin therapy early on.

The prevalence of youth-onset type 2 diabetes has increased because of rising rates of pediatric overweight and obesity, Dr. Magge emphasized. In her experience, the diabetes risk factors that guide the ADA’s screening approach “are so common in overweight and obese youth that they all have at least one.”

The NHANES data did not contain information on all the variables that make up the current diabetes screening criteria in youth; there was no explicit information on history of maternal gestational diabetes and family history of type 2 diabetes, for instance, or the presence of acanthosis nigricans or polycystic ovarian syndrome – conditions associated with insulin resistance. The investigators said it’s likely, therefore, that the study underestimated the number of U.S. youth who would be eligible for diabetes screening.

And, as Dr. Magge said, “it is difficult to determine which risk factors [in the ADA guidelines] were less predictive.”

The NHANES analysis covered 14,119 youth in the 1999-2016 NHANES surveys, which consisted of interviews and standardized physical exams, including laboratory tests, in home and at a mobile examination center. Analyses involving any fasting lab tests were limited to a random subsample of participants aged 12-19 years without diagnosed diabetes who were asked to fast the night before; 6,225 youth properly followed instructions and were included in this subsample.

The surveys are conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention. The study authors and the editorial author indicated that they have no relevant financial disclosures or conflicts of interest. Dr. Magge also said she has no relevant disclosures.

SOURCE: Wallace AS et al. Pediatrics. August 2020. doi: 10.1542/peds.2020-0265.

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