As suggested by population-based studies conducted in the US as part of the NHTN NES programme, healthy children have significantly lower ALT activity compared to adults.
The upper limit of normal for the so-called liver tests, alanine (ALT) and aspartate (AST) aminotransferases, is the same for children and adults in most laboratories. Meanwhile, as suggested by population-based studies conducted in the US as part of the NHTN NES programme, healthy children have markedly lower ALT activity compared to adults and the tacitly accepted upper limit of the ALT norm of approximately 40-50 units may be overestimated, leading to reduced sensitivity for detecting liver pathology in children. Statistical analysis of the NHTN NES study conducted between 1999 and 2006 on a group of children numbering in the thousands shows that the 95th percentile of ALT values for healthy children of normal weight is 25.8 U/L for boys and 22.1 U/L for girls.
Of course, adopting such upper limit values of the norm increases the risk of false positives and unnecessary clinical diagnosis, but in the opinion of the authors, the norm ranges adopted to date with an upper limit of up to 50 U/L seem too liberal and risk overlooking the developing liver pathology in the child.