GPT and infectious disease: Initially, he was referred to the infectious disease clinic at a local hospital where serological tests showed positive hepatitis B surface antigen (HBsAg), an alanine aminotransferase (ALT) level of 162 IU/L (9–50 IU/L), and an aspartate transaminase (AST) level of 121 IU/L (9–50 IU/L).