Liver Function Test

Aka: Liver Function Test, LFT

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II. Background

  1. The term "Liver Function Test" or LFT is used for convenience and brevity, but is a misnomer
  2. The only true Liver Function Tests are those of synthetic function (e.g. INR)
    1. Transaminases are instead markers of hepatocellular disease
    2. Bilirubin and Alkaline Phosphatase are markers of cholestasis
  3. However, hepatology has failed to give the rest of us a convenient, more descriptive term to replace LFTs
    1. As with MASLD, they will no doubt replace LFT with a term twice as long, and more difficult to remember

III. Labs: Markers of liver function and Protein synthesis

  1. Serum Albumin
  2. Serum Bilirubin
  3. Prothrombin Time (PT/INR)

IV. Labs: Markers of hepatocellular disease

  1. Alanine Aminotransferase (ALT)
    1. Most specific for hepatocyte injury
  2. Aspartate Aminotransferase (AST)
    1. Less specific than ALT (present outside liver)
  3. AST to ALT ratio
    1. Most liver conditions (e.g. NASH): Ratio <1
    2. Alcoholism: Ratio >2
    3. Wilson's Disease >4
  4. Lactate Dehydrogenase (LDH)
    1. Least specific for hepatocyte injury
    2. Dramatically increased in ischemic hepatitis
    3. Increased with alk phos in liver metastases

V. Labs: Markers of cholestasis

  1. Alkaline Phosphatase
  2. Serum Bilirubin
  3. Gamma Glutamyl Transferase (GGT)

VI. Labs: Disease specific markers

  1. Definite value
    1. Viral Hepatitis Serology
    2. Iron studies
    3. Ceruloplasmin (Wilson's Disease)
  2. Limited value: Anti-Smooth Muscle Ab
    1. Antimitochondrial Antibody
    2. Alpha-1 Antitrypsin

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