bilirubin upper normal limit total uln institutional times gilberts syndrome aminotransferase ast alt aspartate alanine uln upper normal limit times limits normal institutional bilirubin total upper creatinine serum potassium uln normal limit upper creatinine uln serum times institutional alt ast creatinine uln serum times institutional renal days registration obtained prior liver uln disease metastases chronic cirrhosis alt ast hepatitis patients alkaline phosphatase uln limit normal upper liver alp times bone wort st phenytoin carbamazepine phenobarbital cypa rifampin johns inducers rifabutin lipase amylase uln serum pancreatitis radiologic normal clinical pancreatic evidence