An Assessment of Upper Limits of Normal for ALT and the Impact on Evaluating Natural Course of Chronic Hepatitis B Virus Infection in Chinese Children

BACKGROUND: The current upper limits of normal (ULN) for serum alanine aminotransferase (ALT) are increasingly challenged. We aimed to re-evaluate the ULN for ALT and assess the potential impact on the classification of natural course of chronic hepatitis B virus (HBV) infection in children. METHODS: Laboratory data obtained from three hospitals in China were retrospectively analysed. In total, 2054 children with chronic HBV infection and 8149 healthy children at age ≤18 years were included in the study. RESULTS: Age-specific and gender-specific ULNs for ALT, at averages of 30 U/L for boys and 24 U/L for girls, were calculated from the data of healthy children. Using the revised ULNs vs. the current ULNs (40-50 U/L), 31-60% vs. 9-17% of the 2054 HBV-infected children had an abnormal result as seen in their ALT baseline analysis, and the highest abnormality rate was seen in the infants. Data of 516 HBV-infected children were applied for the classification of clinical phase, 28.8% vs. 19.8% of the children were classified into the phases of hepatitis B e antigen (HBeAg-)positive/negative hepatitis. During a median follow-up of 62 months, 39 of 153 children underwent HBeAg seroconversion, whereas 3 of them had persistently "normal" ALT, according to the current ULN. CONCLUSIONS: The revision of ULN for ALT in children substantially impacts the classification of the natural course of chronic HBV infection. Mild ALT fluctuation is common during the stage childhood, suggesting a need to rethink the current conceptions of immune tolerance and natural course of chronic HBV infection in the children.