What is the recommended screening test for diabetes mellitus (DM) in pediatric patients?

Screening for Diabetes Mellitus in Children

In children, screen for type 2 diabetes using fasting plasma glucose (FPG), 2-hour oral glucose tolerance test (OGTT), or HbA1c—all three tests are acceptable screening options according to current guidelines. 1

Who Should Be Screened

Begin screening after the onset of puberty or at age ≥10 years (whichever comes earlier) in children with overweight (BMI ≥85th percentile) or obesity (BMI ≥95th percentile) who have one or more additional risk factors. 1

Additional Risk Factors That Trigger Screening:

• Family history of type 2 diabetes in first- or second-degree relatives 1
• Race/ethnicity associated with increased diabetes risk (African-American, Hispanic-American, Native American, Asian-American, Pacific Islander) 1
• Signs of insulin resistance or conditions associated with it (acanthosis nigricans, hypertension, dyslipidemia, polycystic ovary syndrome) 1
• Maternal history of diabetes or gestational diabetes during the child's gestation 1

Screening Test Options

All three tests—FPG, 2-hour OGTT, and HbA1c—are appropriate for screening, though each has distinct advantages and limitations. 1

Fasting Plasma Glucose (FPG):

• Requires 8 hours of fasting 1
• More practical than OGTT (single blood draw) 2
• Diagnostic threshold: ≥126 mg/dL (7.0 mmol/L) 1
• Prediabetes range: 100-125 mg/dL (5.6-6.9 mmol/L) 1, 3

2-Hour Oral Glucose Tolerance Test (OGTT):

• Uses 75g anhydrous glucose load (or 1.75 g/kg up to maximum 75g in children) 1
• Most sensitive for detecting impaired glucose tolerance 1, 2
• Diagnostic threshold: ≥200 mg/dL (11.1 mmol/L) at 2 hours 1
• Major disadvantages: low reproducibility, inconvenience, requires fasting 2

HbA1c:

• Most convenient option (no fasting required) 2
• Must be performed in a laboratory using NGSP-certified method 1
• Point-of-care assays should NOT be used for diagnosis 1
• Diagnostic threshold: ≥6.5% (48 mmol/mol) 1
• Prediabetes range: 5.7-6.4% (39-47 mmol/mol) 1

Screening Frequency

If initial screening is normal, repeat testing at minimum 3-year intervals, or more frequently if BMI is increasing. 1

Diagnostic Confirmation

In the absence of unequivocal hyperglycemia, diagnosis requires two abnormal test results—either from the same test on different days, or two different tests (e.g., HbA1c and FPG) on the same day. 1, 4

Exception: A random plasma glucose ≥200 mg/dL (11.1 mmol/L) with classic symptoms (polyuria, polydipsia, unexplained weight loss) confirms diabetes without need for repeat testing. 1, 3

Critical Diagnostic Considerations

Distinguishing Type 1 from Type 2 Diabetes:

In overweight/obese children being evaluated for type 2 diabetes, measure pancreatic autoantibodies (GAD65, IA-2, ZnT8, insulin autoantibodies) to exclude autoimmune type 1 diabetes. 1, 4

This is essential because:

• Overweight and obesity are increasingly common in children with type 1 diabetes 1
• Approximately 10% of youth with type 2 diabetes phenotype have islet autoimmunity 1
• DKA occurs in ~6% of youth with type 2 diabetes at onset 1
• Treatment regimens differ markedly between the two types 1

Consider measuring C-peptide levels, which are typically low or undetectable in type 1 diabetes but preserved in type 2 diabetes. 1, 4

Important Caveats and Pitfalls

HbA1c Limitations:

Do not use HbA1c in children with conditions affecting red blood cell turnover (sickle cell disease, recent blood loss, transfusion, hemoglobinopathies). 1, 4 In these cases, use only plasma glucose criteria 4.

Stress Hyperglycemia:

In young children with acute illness, incidental hyperglycemia may represent stress hyperglycemia rather than diabetes—consultation with pediatric endocrinology is indicated before diagnosing diabetes. 1, 4, 3

Sample Handling:

Ensure prompt processing and proper storage of glucose samples to avoid falsely low results from glycolysis. 4

Combination Screening Strategy:

Combining HbA1c ≥5.7% with FPG ≥100 mg/dL improves sensitivity to 95.5% and provides better ability to rule out prediabetes (negative likelihood ratio 0.07) compared to either test alone. 5 This combination approach may be particularly useful in clinical practice to determine which children require full OGTT evaluation 5.

Type 1 Diabetes Screening

Routine screening for type 1 diabetes in asymptomatic children is NOT recommended outside of research studies, even in first-degree relatives of patients with type 1 diabetes. 1, 6