GPT and skeletal muscle disorder: Although ALT is considered a more specific indicator of liver disease, the concentration of AST may be a more sensitive indicator of liver injury in conditions such as alcohol-related liver disease and in some cases of autoimmune hepatitis (AIH).31 32 In children, creatine kinase measurement may help to determine whether an isolated rise in ALT or AST is due to an underlying skeletal muscle disorder, such as muscular dystrophy.