Liver Function Tests Quiz

Liver Function Tests

• Liver function tests are used to assess liver health and identify potential issues.
• These tests evaluate different aspects of liver function, including injury, synthesis, and excretion.

Normal Liver Functions

• Metabolism: The liver plays a vital role in carbohydrate, lipid, and protein metabolism.
• Storage: The liver stores vitamins (like K, D, A, and B12) and iron.
• Excretory Function: The liver excretes bilirubin and other substances.
• Detoxification: The liver detoxifies drugs and ammonia.
• Hematological Functions: The liver is involved in blood formation (fetal life and proerythropoietin in adults), blood coagulation, and blood volume regulation.

Liver Function Tests and Their Interpretation

• Liver function tests are categorized into three groups:
  • Hepatocyte injury: Assessed using AST and ALT. Elevated levels indicate damage to the liver cells.
  • Synthetic function: Evaluated using albumin and prothrombin time (PT). Low levels can suggest liver damage.
  • Cholestasis or Excretory function: Assessed using bilirubin, ALP, and GGT. Elevated levels may indicate issues with bile flow.
  • Enzymes: Grouped into two categories:
    • Enzymes that reflect hepatocyte damage: Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT).
    • Enzymes showing cholestasis: Alkaline phosphatase (ALP), Gamma-glutamyl transpeptidase (GGT), and 5'–nucleotidase.

Uses of Liver Function Tests

• Screening: Liver function tests are non-invasive and a sensitive screening method for detecting liver dysfunction.
• Disease pattern recognition: These tests can differentiate between various liver diseases like acute viral hepatitis, chronic liver disease (CLD), and cholestatic disorders.
• Severity assessment: Used to assess the severity and predict the outcome of specific liver diseases.
• Follow-up and treatment evaluation: Monitor the progression of liver diseases and the response to treatment.

Enzymes (Details)

• Alanine transaminase (ALT): Elevated levels specifically indicate liver damage.

  • It is more specific to the liver than AST.
  • Its source: liver > heart > kidney > skeletal muscle > spleen
  • Causes of high ALT:
    • Acute viral hepatitis, Toxic liver necrosis
    • Liver cirrhosis, Cholestatic jaundice
    • Liver congestion, Alcoholic Hepatitis, and Malignant liver infiltration
    • Chronic viral hepatitis, Hemochromatosis, Fatty liver.

• Aspartate aminotransferase (AST): Elevated levels indicate liver damage but can also originate from other organs like the heart.

  • Causes of high AST:
    • Physiological (newborns), Liver cirrhosis, Cholestatic jaundice, Malignant liver infiltration, Skeletal muscle and Myocardial infarction
    • Acute viral hepatitis, Toxic liver necrosis

• Alkaline phosphatase (ALP): Elevated levels indicate cholestasis (obstruction of bile flow).

  • Causes of high ALP: Pregnancy, Children (higher osteoblastic activity), Preterm infants (higher ALP levels), Medication (e.g., sulfonamides), Primary biliary cirrhosis, Stones, Malignancy, Pancreatitis

• Gamma-glutamyl transpeptidase (GGT): A sensitive marker for cholestasis, cirrhosis, and carcinoma. Useful in excluding bone disease and often elevated with alcohol toxicity.

• 5' Nucleotidase: Another specific test for cholestasis or damage to intra or extra hepatic biliary system levels.

Bilirubin

• Bilirubin is a breakdown product of red blood cells.

• Elevated bilirubin levels can lead to hyperbilirubinemia and jaundice.

• Types: Direct (conjugated) and indirect (unconjugated).

• Elevated direct bilirubin suggests problems with the biliary system.

• Elevated indirect bilirubin suggests problems with red blood cell breakdown.

• Increased bilirubin levels cause dark urine, light-colored stools.

• Clinical Classifications of Hyperbilirubinemia/Jaundice: Categorized as prehepatic, hepatic, or posthepatic (obstructive). These classifications differentiate based on which stage of bilirubin processing is affected.

Plasma Proteins

• The liver is the major source of most plasma proteins, including albumin and globulins (α, β and γ).

• Albumin: Synthesized exclusively by the liver. 40-60% of total plasma protein.

• Globulins: Synthesized primarily by the liver (α and β). elevated gamma globulins could be chronic hepatitis or cirrhosis (IgG in autoimmune & IgA in alcoholic liver disease).

• A/G Ratio: The ratio of albumin to globulin. It helps diagnose liver disease, typically a 2:1 ratio is normal.

Prothrombin Time (PT)

• PT measures the time it takes for blood to clot.
• The liver is essential for producing clotting factors.
• Low albumin and prolonged PT suggest significant liver damage as the liver produces clotting factors.
• Low albumin and prolonged PT suggest significant liver damage. Vitamin K deficiency causes prolonged PT

Liver Function Test Normal Values (Approximate)

• Specific values can vary. Consult lab reports for precise details.
• This table provides general normal ranges for common liver function tests and should not be taken as definitive.

Algorithms for Liver Disease Diagnosis

• Algorithms using liver function tests help determine the type of liver disease, if the underlying cause appears to be hepatocellular or cholestatic.

Test your knowledge about liver function tests with this comprehensive quiz. Explore important concepts such as albumin synthesis, prothrombin levels, and the implications of altered liver function test results. Ideal for students and professionals interested in hepatology.