What laboratory tests are recommended for pediatric obesity screening?

Laboratory Screening for Pediatric Obesity

Children with obesity (BMI ≥95th percentile) should be screened with a lipid panel starting at age 2 years if obese, fasting glucose at age 10 years (or earlier if additional diabetes risk factors present), and ALT for NAFLD screening between ages 9-11 years, with additional metabolic testing based on age and comorbidity burden. 1

Core Laboratory Tests by Age and BMI Category

For Children with Obesity (BMI ≥95th percentile):

Lipid Screening:

• Begin at age 2 years when obesity is present 1
• Obtain fasting lipid profile (total cholesterol, LDL, HDL, triglycerides) 1
• Confirm abnormal values 2 weeks to 3 months after initial screen 1

Glucose/Diabetes Screening:

• Start at age 10 years for children with obesity AND 2 additional diabetes risk factors 1
• Use fasting glucose as the screening test 1
• Additional risk factors include: family history of type 2 diabetes, signs of insulin resistance (acanthosis nigricans), or presence of other metabolic syndrome components 1

Liver Function Testing (NAFLD Screening):

• Screen children aged 9-11 years with obesity using ALT 1
• Gender-specific thresholds: ALT ≥26 IU/L for boys, ≥22 IU/L for girls suggests NAFLD 1
• AST can be included but ALT is the preferred screening test 1
• Consider abdominal ultrasound when ALT is elevated or when additional confirmation is needed 1

For Children with Overweight (BMI 85th-94th percentile):

Without Additional Risk Factors:

• Fasting lipid profile is recommended 2
• Other testing generally not indicated unless specific risk factors present 2

With Metabolic Risk Factors:

• Same comprehensive screening as obese children 1
• Metabolic risk factors include: insulin resistance, type 2 diabetes, dyslipidemia, hypertension, or abdominal obesity 1
• For NAFLD screening, overweight children with insulin resistance, pre-diabetes, diabetes, or dyslipidemia should have ALT measured 1

Additional Laboratory Considerations

Comprehensive Metabolic Panel:

• For children with BMI >95th percentile, consider BUN and creatinine 2
• This is particularly important when obesity-related illnesses are already present 2

When ALT is Elevated (Suggesting NAFLD):

• AST should also be measured if not already done 1
• Consider additional non-invasive assessment with abdominal ultrasound 1
• Liver fibrosis scans or MRI-PDFF can be performed for further evaluation 1

Important Clinical Caveats

Age-Specific Considerations:

• NAFLD screening before age 9 may be appropriate when risk is particularly high (strong family history, severe obesity, metabolic syndrome), though no specific algorithm exists for defining this high-risk group 1
• The rationale for starting NAFLD screening at ages 9-11 is that this coincides with pubertal changes in insulin resistance and body composition that increase NAFLD risk 1

Interpretation Pitfalls:

• Normal ALT does not exclude NAFLD—sensitivity is only approximately 50% at commonly used thresholds 1
• ALT correlates with steatosis and insulin resistance rather than inflammation or fibrosis 1
• Ultrasound also has limited sensitivity (approximately 52%) but high specificity (96%) when using standardized scoring 1

Screening Gaps in Practice:

• Real-world data shows only 22% of diagnosed obese children receive all three recommended screening tests (glucose, liver, lipids) 3
• Screening rates improve with increasing BMI and age, but remain suboptimal even after obesity diagnosis 3
• Female and Hispanic patients are more likely to be screened in practice 3

Practical Implementation

Laboratory Panel Organization:

• Order as "basic metabolic panel" for glucose/renal function 3
• Order as "hepatic function panel" for liver enzymes 3
• Order as "full lipid profile" for cardiovascular risk assessment 3

Timing of Screening:

• Fasting samples are required for glucose and lipid testing 1
• Screen at least annually once obesity is identified 2
• More frequent monitoring may be needed if abnormalities are detected 4