What laboratory tests should be performed on an obese or overweight child?

Laboratory Testing for Overweight and Obese Children

All overweight and obese children should undergo laboratory screening for diabetes, liver abnormalities, and dyslipidemia to identify obesity-related comorbidities that impact morbidity, mortality, and quality of life. 1

Who Should Be Screened

Primary Screening Criteria

• All children with obesity (BMI ≥95th percentile for age and sex) should undergo laboratory screening 1
• Children with overweight (BMI ≥85th percentile but <95th percentile) who have additional risk factors should also be screened 1

Risk Factors That Warrant Screening in Overweight Children

• Family history of type 2 diabetes (first or second-degree relatives) 1
• High-risk race/ethnicity (African American, Latino, Native American, Asian American, Pacific Islander) 1
• Signs of insulin resistance (acanthosis nigricans) 1
• Hypertension 1
• Dyslipidemia 1
• Polycystic ovary syndrome 1
• Maternal history of diabetes or gestational diabetes during the child's gestation 1

Recommended Laboratory Tests

Diabetes/Glucose Metabolism Screening

• Fasting plasma glucose (FPG) 1
• Hemoglobin A1C 1
• Consider oral glucose tolerance test (OGTT) in high-risk patients, especially when other tests are normal but clinical suspicion is high 1, 2

Liver Function Screening

• Alanine aminotransferase (ALT) to screen for non-alcoholic fatty liver disease (NAFLD) 1
  • ALT >35 IU/L has high specificity (94%) for detecting NAFLD 1
  • Consider abdominal ultrasound for those with elevated ALT 1

Lipid Screening

• Full lipid profile (total cholesterol, LDL, HDL, triglycerides) 1, 3
  • Low HDL (<35 mg/dL) and/or elevated triglycerides (>250 mg/dL) are particularly associated with insulin resistance 1

Age to Begin Screening

• For type 2 diabetes screening: begin at age 10 years or at onset of puberty, whichever occurs first 1
• For NAFLD screening: the North American Society of Pediatric Gastroenterology, Nutrition and Hepatology recommends beginning between ages 9 and 11 1
• For lipid screening: begin at the time obesity is identified 3

Frequency of Testing

• If initial tests are normal, repeat screening at least every 3 years 1
• More frequent testing (annually) is recommended for:
  • Children with prediabetes (A1C ≥5.7%, impaired fasting glucose, or impaired glucose tolerance) 1
  • Children whose BMI is increasing 1
  • Children with worsening risk factors 1

Interpretation of Results

Diabetes/Prediabetes

• Prediabetes is defined as:
  • FPG 100-125 mg/dL (impaired fasting glucose) 1
  • 2-hour glucose during OGTT 140-199 mg/dL (impaired glucose tolerance) 1
  • A1C 5.7-6.4% 1
• An A1C ≥5.5% has been shown to have good sensitivity (85.7%) for identifying impaired glucose tolerance 4

NAFLD

• ALT >35 IU/L has a positive predictive value of 79% for NAFLD in populations with high prevalence 1
• Ultrasound score ≥2 has high specificity (96%) for detecting hepatic steatosis 1

Common Pitfalls and Caveats

• Screening rates for obesity-related complications remain suboptimal, with studies showing only 22% of obese children receive comprehensive screening for diabetes, liver, and lipid abnormalities 5
• ALT and ultrasound alone cannot definitively diagnose NAFLD or determine the presence of inflammation or fibrosis 1
• A1C may be affected by hemoglobinopathies, anemia, or conditions with increased red cell turnover; in these cases, only blood glucose criteria should be used 1
• Fasting glucose alone may miss many cases of prediabetes; consider additional testing with A1C or OGTT in high-risk patients 2, 4
• The accuracy of ultrasound for NAFLD is highly dependent on operator experience 1

By implementing comprehensive laboratory screening for overweight and obese children, clinicians can identify metabolic complications early, intervene appropriately, and potentially prevent progression to more serious conditions that affect long-term morbidity and mortality.