In China, a more extensive population ALT screening was conducted in the 1960s, and asymptomatic elevated serum ALT accounted for about 5-10% of the population. After the development of HBsAg testing, it was found that the detection rate of HBsAg was three times higher in those with abnormal ALT than in those with normal, and nearly half of those with single ALT elevation were hepatitis B without xanthogranuloma. So what is the differential diagnosis for elevated single alt? Here’s a look together. 1, biliary atresia: mainly when jaundice is present to differentiate from pathological jaundice in the neonatal period. Hepatitis B is hepatic jaundice, serum bilirubin is biphasic, but in the early neonatal period, because the hepatocyte excretion function is first blocked, the appearance of obstructive jaundice, so it is most important to distinguish from biliary atresia. As the latter must aim to operate after a clear diagnosis within the first 3 months of life. The two can be differentiated from each other in the following aspects: (1) Medical history: poor general condition and appetite in the early stages of hepatitis B, possible fluctuations in the degree of jaundice, fluctuations in the white clay-colored stools, insignificant degree of hepatosplenomegaly, and high early transaminases. (2) Serum fetal alpha globulin: significantly increased in hepatitis B, often greater than 1600 ng/ml. (3) Iodine rosacea excretion test: increased 131I rosacea excretion in hepatitis B after taking phenobarbital or kaufenamide, but no change in biliary atresia. (4) Vitamin E absorption test: oral administration of vitamin E in hepatitis B reduced the hemolytic effect on hydrogen peroxide, while it did not improve in biliary atresia. (5) Lipoprotein X assay: negative for lipoprotein X in hepatitis B, positive in biliary atresia. (6) Other: such as 99mTc-IDA imaging, B-mode ultrasonography, percutaneous liver biopsy, duodenal fluid bile pigment examination is more meaningful for the diagnosis of biliary atresia. 2, metabolic defect disease: such as galactosemia, α1-antitrypsin deficiency, etc. The disease is transmitted directly from mother to fetus by mother with hepatitis B. The incidence of neonatal disease is high. Laboratory tests help in the differential diagnosis.