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Liver Function Tests
 
 
Liver Function Tests
Liver function tests are used to assess for evidence of acute or chronic liver disease. Patterns of derangement include hepatocellular dysfunction, cholestatic change and changes of cirrhosis. 
 

Lactate Dehydrogenase

 
 

Overview

  • Lactate dehydrogenase (LDH) is an enzyme present in the cytoplasm of most cells that catalyses the conversion of lactate to pyruvate.
  • As LDH is present in all tissues, its elevation is a nonspecific marker of cell damage. Elevation of specific LDH isoenzymes may point toward a specific pathology, as below.
    • Causes of Elevated Lactate Dehydrogenase

    • Factitious (haemolysed sample)
    • Heart - myocardial infarction, heart failure
    • Brain - ischaemic stroke, traumatic brain injury
    • Kidneys - nephritis, nephrotic syndrome, acute tubular necrosis, infarction
    • Anaemia - haemolytic or megaloblastic
    • Malignancy (especially haematological)
    • Lungs - pulmonary embolism, infarction, obstructive disease, interstitial lung disease, pneumonia
    • Spleen - infarction
    • Pancreas - pancreatitis
    • Liver - hepatitis, infarction, cirrhosis, malignancy, trauma
    • Skeletal muscle - strenuous exercise, rhabdomyolysis, myositis
    • Shock
    • Trauma
    • Hypoxia

LDH Isoenzymes

  • There are five LDH isoenzymes composed of two H (heart) and M (muscle) subunits. The isoenzymes are classified depending on their migration on electrophoresis.
  • The isoenzyme electrophoresis pattern is relatively non-specific, though specific patterns of isoenzyme elevation are classically (yet loosely) associated with certain diseases.
    • Interpretation

    • Elevated LDH1 and LDH2 - myocardial infarction, brain injury, renal pathology, haemolytic or megaloblastic anaemias
    • LDH1 > LDH2 (‘flipped’ LDH) - myocardial infarction
    • Elevated LDH2 and LDH3 - acute leukaemia
    • Elevated LDH3 and LDH4 - splenic or lung pathology
    • Elevated LDH5 - liver or skeletal muscular pathology
Last updated on November 25th, 2019
 
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