Approach to the Patient with Abnormal Liver Tests

Understanding patterns of abnormal liver tests can aid in the diagnosis of many causes of liver disease. Serologic liver tests are broadly divided into those that evaluate liver function (prothrombin time, bilirubin, albumin), those that evaluate integrity of hepatocytes (aspartate aminotransferase or AST, alanine aminotransferase or ALT) and those that assess abnormalities of bile ducts and bile flow (bilirubin, alkaline phosphatase or AP, gamma glutamyl transpeptidase or GGT). Patterns of abnormal liver tests include hepatocellular (AST and ALT elevation), cholestatic (bilirubin, AP, GGT) and mixed elevations. Causes of a hepatocellular pattern of injury include alcoholic hepatitis, non-alcoholic steatohepatitis, viral hepatitis, drug-induced liver injury and autoimmune hepatitis. Diseases that cause cholestatic elevations include primary sclerosing cholangitis, primary biliary cirrhosis and obstruction of bile ducts. Acute liver failure and cirrhosis are conditions that lead to impaired liver function and are characterized by abnormal prothrombin time, bilirubin and albumin.