Normal ALT Range in Pediatric Patients
The normal upper limit of ALT in children should be gender-specific: ≤26 IU/L for boys and ≤22 IU/L for girls, based on the 95th percentile of healthy pediatric populations. 1
Evidence-Based Gender-Specific Thresholds
The American Association for the Study of Liver Diseases recommends these gender-specific cutoffs for NAFLD screening in children aged 9-11 years, which represent the most clinically validated thresholds 1. These values are substantially lower than traditional laboratory reference ranges that many institutions still use (often 30-90 IU/L), which are set too high to reliably detect pediatric liver disease 2.
Age-Related Considerations
- Infants and toddlers (<18 months): Higher upper limits apply, with 95th percentile values of 60 IU/L for boys and 55 IU/L for girls 3
- Children >18 months: Values decrease to 40 IU/L for boys and 35 IU/L for girls by some European data 3
- School-age and adolescents: The most widely accepted thresholds remain 26 IU/L (boys) and 22 IU/L (girls) 1, 4, 2
ALT levels decrease significantly with increasing age in childhood, and girls consistently have lower values than boys across all age groups 4, 3.
Clinical Context for Interpretation
For Screening Purposes (NAFLD Detection)
At the recommended thresholds of 22-26 IU/L, sensitivity is approximately 72-82% with specificity of 79-85% for detecting liver disease 2. This represents an optimal balance—higher thresholds (30-40 IU/L) achieve 90% specificity but miss half of affected children 5.
For Treatment Decisions (Chronic Hepatitis B)
Different, higher thresholds apply when considering antiviral therapy. Children with chronic hepatitis B should have ALT >60 IU/L (1.5 times the traditional upper limit of 40 IU/L) on at least two occasions over 6 months before treatment is considered 5, 6. This higher bar reflects the need for clear evidence of immune-active disease before initiating potentially long-term therapy.
Critical Pitfalls to Avoid
- Normal ALT does not exclude liver disease: Even at optimal thresholds, ALT has only 50% sensitivity for detecting NAFLD at higher cutoffs (30-40 IU/L), and ALT correlates with steatosis and insulin resistance rather than inflammation or fibrosis 5, 1
- Traditional lab ranges miss disease: Using institutional upper limits of 40-53 IU/L results in sensitivities of only 32-48% for detecting chronic liver disease in children 2
- BMI affects interpretation: Serum ALT levels correlate significantly with BMI, and obese children may have elevated ALT from NAFLD even when values fall in the "normal" range by traditional standards 4, 7
Practical Application Algorithm
- Use gender-specific thresholds: Boys ≤26 IU/L, girls ≤22 IU/L as upper limits of normal 1, 2
- For infants <18 months: Apply higher age-specific ranges (60 IU/L boys, 55 IU/L girls) 3
- Consider metabolic context: In obese children, even "normal" ALT by traditional standards may indicate liver injury—revised thresholds improve detection of mild NAFLD 7
- Persistent elevation matters: For treatment decisions in chronic hepatitis B, require elevation >60 IU/L on multiple occasions over 6-12 months 5, 6