Diagnosis of Prediabetes in a 9-Year-Old with A1C 5.9%
An A1C of 5.9% alone is insufficient to diagnose prediabetes in a 9-year-old child, and confirmatory testing with fasting plasma glucose or oral glucose tolerance test is required before making this diagnosis.
Why A1C Alone Is Inadequate in Children
The American Diabetes Association guidelines explicitly state that A1C criteria for prediabetes and diabetes diagnosis were developed from epidemiological studies that included only adult populations, making it unclear whether the same A1C cutoff points should be applied to children and adolescents 1. This is a critical limitation that directly affects your patient.
Risk-based screening should be performed using multiple testing modalities, not A1C alone 1. The 2024 ADA Standards specifically recommend that fasting plasma glucose, 2-hour plasma glucose during a 75-g oral glucose tolerance test, AND A1C can all be used to test for prediabetes or diabetes in children and adolescents 1. The key word here is "and"—these tests complement each other rather than standing alone.
The Evidence Against Using Adult A1C Cutoffs in Children
Multiple research studies demonstrate that applying adult A1C criteria (5.7-6.4% for prediabetes) significantly underestimates the prevalence of prediabetes and diabetes in the pediatric population 2, 3. In obese children and adolescents specifically:
- An A1C threshold of 5.8% showed only 68% sensitivity and 78% specificity for detecting type 2 diabetes 2
- The optimal A1C cutoff for prediabetes in Korean obese youth was found to be 5.8%, with an AUC of 0.795 4
- Normal weight youth in the HEALTHY Study showed that 2% had A1C ≥5.7%, suggesting these values may occur in healthy children 5
The kappa coefficient for agreement between OGTT and A1C in children is only 0.464, indicating poor concordance 4. This means A1C and glucose-based tests frequently disagree in pediatric patients.
Required Confirmatory Testing
For your 9-year-old patient with A1C 5.9%, you must obtain:
- Fasting plasma glucose (≥100 mg/dL but <126 mg/dL indicates prediabetes) 1, 6
- 2-hour plasma glucose during 75-g OGTT (≥140 mg/dL but <200 mg/dL indicates prediabetes) 1, 6
The ADA recommends that if two different tests (such as A1C and fasting plasma glucose) are both above the diagnostic threshold, this confirms the diagnosis 1. However, given the poor performance of A1C in children, the combination of fasting and 2-hour glucose levels, in addition to A1C, is recommended for diagnosis of childhood prediabetes 4.
Additional Diagnostic Considerations
Screen for risk factors that warrant testing 1:
- BMI ≥85th percentile (overweight) or ≥95th percentile (obesity)
- Family history of type 2 diabetes in first- or second-degree relatives
- Signs of insulin resistance (acanthosis nigricans, hypertension, dyslipidemia, polycystic ovary syndrome)
- Maternal history of diabetes or gestational diabetes during the child's gestation
Consider testing for type 1 diabetes markers if proceeding with diabetes evaluation 1. Children and adolescents with overweight or obesity in whom type 2 diabetes is being considered should have pancreatic autoantibodies tested to exclude autoimmune type 1 diabetes, as distinguishing between types can be difficult in this age group 1.
Critical Pitfalls to Avoid
Do not diagnose prediabetes based solely on A1C in a child 2, 3. The adult cutoff of 5.7% has been shown to have low sensitivity and specificity in pediatric populations and may lead to overdiagnosis in normal-weight children or underdiagnosis in obese children.
Hemoglobin variants can interfere with A1C measurement 1. If there is marked discordance between A1C and plasma glucose levels, consider that the A1C assay may not be reliable for this individual.
Conditions affecting red blood cell turnover invalidate A1C testing 1, 6. In children with sickle cell disease, recent blood loss, or other conditions affecting erythrocyte lifespan, use only plasma glucose criteria for diagnosis.
Follow-Up Recommendations
If confirmatory testing reveals prediabetes, repeat screening at minimum 3-year intervals, or more frequently if BMI is increasing 1. Given that BMI and family history of diabetes are the strongest predictors of progression to diabetes 7, more aggressive monitoring is warranted in children with these risk factors.