Curriculum · Gastroenterology
Approach to abnormal liver function tests
What it is
The liver panel is total and direct (conjugated) bilirubin, ALT, AST, ALP, PT, GGT and albumin, and reading it turns on two things: whether the bilirubin is conjugated or not, and whether the enzyme pattern is hepatocellular or cholestatic. Mild asymptomatic elevations, under 5 times the upper limit of normal, of ALT and AST are common in primary care, and it is estimated that approximately 10% of the U.S. population has elevated transaminase levels.
The injury patterns are three. Hepatocellular injury shows elevated ALT, which is more specific than AST, and ALP, which is more sensitive, with or without GGT and bilirubin. Cholestasis shows elevated ALP, GGT and bilirubin, with or without ALT and AST. The third is mixed.
Causes and risk
The most common causes of elevated transaminase levels are nonalcoholic fatty liver disease and alcoholic liver disease. In pregnancy two causes are worth holding: obstetric cholestasis, whose main complaint is pruritis in palms and soles, and acute fatty liver of pregnancy, which presents with RUQ abdominal pain, nausea, malaise, prolonged PT, deranged liver function tests and raised bilirubin with mild jaundice, and which occurs in the third trimester or immediately following delivery. A transfused patient carries a different pair: in a boy with beta thalassemia major on regular blood transfusions who is not very compliant with chelation therapy, the two causes of deranged liver enzymes are iron overload and viral hepatitis, with a drug side effect of the chelators also acceptable.
Anemia beside the jaundice points further. Anemia with unconjugated hyperbilirubinemia and normal liver transaminases supports autoimmune hemolytic anemia, which may be precipitated by antibiotic or other drug exposure and whose symptoms include clinical jaundice and anemia that may cause impaired exercise tolerance. Normal liver transaminases make viral hepatitis and infectious mononucleosis unlikely, Gilbert syndrome is not associated with anemia, and cholelithiasis is associated with conjugated hyperbilirubinemia. A hemoglobin of 83 where 123 to 157 is normal, a total bilirubin of 85 where under 26 is normal, a direct bilirubin of 5 where under 7 is normal, an alanine aminotransferase of 36 at the top of a 3 to 36 range and a gamma glutamyl transferase of 10 at the low end of a 10 to 30 range is that picture.