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 rise in PBC.
• Lactate dehydrogenase elevated in haemolysis.
• LFTs:
  • Alkaline phosphatase: The most common diseases associated with elevated alkaline phosphatase include:
    • Gallstones causing bile duct obstruction
    • Pancreatic cancer
    • Pregnancy
    • Drugs
    • More rarely, PBC
  • Serum transaminases are usually very high in viral hepatitis.
    • 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):
    • 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