Evaluation of Abnormal Liver Biochemical Test Results

Liver biochemical and function tests-alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, bilirubin, prothrombin time, and albumin-are used to screen and identify people with acute and chronic liver disease. Elevations in alanine aminotransferase and aspartate aminotransferase reflect hepatocellular injury, with more urgent evaluation required when the international normalized ratio of prothrombin is prolonged and the bilirubin level elevated. An elevation in alkaline phosphatase reflects a cholestatic process and impaired bile flow. Bilirubin may be elevated with either hepatocellular or cholestatic injury. Albumin, prothrombin time, and bilirubin are tests of hepatic function. Evaluation of abnormal liver tests includes history taking with attention to metabolic risk factors, alcohol, medications, and herbal/dietary supplements, followed by an examination, to determine the etiology of liver injury, acuity of illness, and presence of complications. Abdominal imaging provides information regarding liver morphology, steatosis, biliary dilatation, and portal hypertension. Elastography provides information about fibrosis and steatosis. If no explanation for abnormal liver tests can be determined, extrahepatic causes should be investigated. Liver tests used in the estimation of hepatic fibrosis include the fibrosis-4 index and aspartate aminotransferase-to-platelet ratio index. Many proprietary tests of hepatic fibrosis incorporate liver biochemical tests. Liver tests may also be used in the assessment of prognosis, particularly in people with cirrhosis, alcohol-associated liver disease, and metabolic dysfunction-associated steatotic liver disease. Liver test elevations in critically ill patients often reflect severe hepatocellular injury, whereas liver test elevations often indicate hepatotoxicity in people receiving chemotherapy and immune checkpoint inhibitors. With the availability of many approaches to assessing the diagnosis and severity of liver disease, the role of liver biopsy has become more limited.