摘要Background Alanine aminotransferase(ALT)is widely used to screen patients with hepatic diseases.However,the current reference ranges(＜50 U/L)were developed by laboratories and have not been validated in populations with a large number of healthy individuals.Methods This study collected venous blood and anthropometric data from a total of 13,287 healthy children aged 3 months to 18 years who underwent routine physical examinations in the Department of Pediatric Healthcare.We applied the least mean square algorithm to establish age-and sex-related reference percentiles of serum levels of transaminases.For valida-tion,we recruited 4276 children and adolescents with obesity/overweight who underwent evaluation and metabolic tests in the hospital.Using receiver operating characteristic curves,we determined age-and sex-specific upper limit percentiles of liver enzymes for fatty liver diseases.Results This study revealed a significant correlation between serum transaminase levels and age and sex(P＜0.01).These transaminase levels exhibited age-and sex-specific patterns.Among individuals in the non-alcoholic fatty liver disease(NAFLD)cohort,elevated ALT levels displayed a positive association with clinical markers of disease severity,including homeostatic model assessment of insulin resistance,waist-hip ratio,and serum uric acid levels(P＜0.01).According to the receiver operating characteristic curves,ALT levels at the 92.58th percentile for boys and the 92.07th percentile for girls yielded the highest accuracy and specificity.Conclusions This study provides age-and sex-specific reference ranges for ALT,aspartate aminotransferase,and y-glutamyltransferase in Chinese children and adolescents,making it the largest population study to date.Furthermore,the study establishes a precise upper limit for ALT levels,facilitating their use in NAFLD screening.