Jaundice laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Laboratory Findings

• Laboratory findings consistent with the diagnosis of jaundice include:
  • An elevated concentration of serum total bilirubin. the upper limit of normal is >1 mg/dL or >1.3 mg/d in some laboratories. Jaundice usually becomes clinically apparent when the serum total bilirubin concentration is greater than 2 to 3 mg/dL , but threshold for clinically apparent jaundice may vary among patients.
• Hyperbilirubinemia can be further categorized as conjugated or unconjugated:
  • Conjugated hyperbilirubinemia:
    •  Serum conjugated bilirubin concentration >0.4 mg/dL (6.8 micromol/L).
    • Direct bilirubin >1 mg/dL (17 micromol/L) if the total bilirubin is <5 mg/dL (85 micromol/L), or more than 20 percent of the total bilirubin if the total bilirubin is >5 mg/dL(85 micromol/L).
  • Unconjugated hyperbilirubinemia:
    •  Conjugated bilirubin is <1 mg/dL (17 micromol/L) if the total bilirubin is <5 mg/dL, or less than 20 percent of the total bilirubin if the total bilirubin is >5 mg/dL (85 micromol/L).
• FBC detect haemolysis.
  • ESR may be elevated - for example, in PBC.
  • Lactate dehydrogenase is raised in haemolysis.
  • LFTs:
    • Alkaline phosphatase: considerably increased with either extrahepatic or intrahepatic biliary disease. The most common diseases associated with raised alkaline phosphatase include:
      • Gallstones causing bile duct obstruction.
      • Pancreatic cancer.
      • Pregnancy.
      • Drugs.
      • More rarely, PBC.
    • Serum transaminases are usually very high in hepatocellular disease (like viral hepatitis) but more modestly elevated in chronic hepatocellular damage and obstruction:
      • Aspartate aminotransferase (AST) is raised more than alanine aminotransferase (ALT) in cirrhosis, intrahepatic neoplasia, haemolytic jaundice and alcoholic hepatitis.
      • ALT is raised more than AST in acute hepatitis and in extrahepatic obstruction.
      • ALT levels of less than 100 IU/L with jaundice suggest obstructive jaundice.
      • ALT over 400 IU/L suggests diffuse acute hepatocellular damage (for example, in viral hepatitis).
      • ALT between 150-400 IU/L suggests chronic active hepatitis or viral or drug-induced hepatitis.
      • Very high levels of ALT (over 1,000 IU/L) suggest acute parenchymal disease.
    • Gamma-glutamyltransferase (GGT):
      • GGT is sensitive but not specific for excess alcohol intake.
      • A raised MCV with raised GGT is suggestive of alcohol abuse and, if accompanied by raised ALT, suggests liver cell damage.
      • Biliary obstruction and hepatic malignancies cause very high GGT levels (x 10 normal).
      • Raised GGT with raised alkaline phosphatase (over x 3 normal) suggests cholestasis.
  • Hepatitis serology should be done in all patients with cholestasis, as differentiating hepatitis from extrahepatic obstructive causes may be very difficult.
  • Prothrombin time may be prolonged because of vitamin K malabsorption. Injection of vitamin K will correct deficiency in cholestasis but not in parenchymal liver disease.
  • Serum antinuclear antibodies (ANAs), anti-smooth muscle antibody (ASMA): the hallmark of PBC is antimitochondrial antibodies (90-95% of patients with PBC are positive); ANA is positive in 20-50% of patients with PBC.
  • Serum immunoglobulins and serum electrophoresis in acute hepatitis when autoimmune hepatitis is suspected. IgG is raised in acute hepatitis, IgM is raised in autoimmune disease, PBC or chronic infection.
  • Alpha-1-antitrypsin levels: deficiency causes cirrhosis and emphysema.
  • Ferritin to screen for haemochromatosis.

Inalcoholic hepatitis the aspartate aminotransferase:alanine aminotransferase ratio is > 2 (AST:ALT)