Tests to Show Hepatocyte Damage (Parenchyma Enzymes)
Alanine aminotransferase (ALT) and aspartate aminotransferase (AST):
• ALT is found only in the cytoplasm, AST in the mitochondria and cytoplasm.
• ALT is more specific for the liver, while AST may also increase in other systemic pathologies.
• The normal serum value of ALT and AST is 10-40 IU/L.
• Normal ALT and AST levels do not exclude liver disease (may be found to be normal in patients with minimal inflammation or advanced cirrhosis).
• ALT and AST are slightly to moderately elevated in many liver diseases
and is usually under 300 IU/L. These situations are:
Fatty hepatitis (steatohepatitis) (most common cause)
chronic hepatitis
• Conditions where ALT and AST increase significantly (> 1000 IU/L) are as follows:
acute viral hepatitis
toxic hepatitis
Ischemic hepatitis (Acute liver ischemia or acute heart failure)
acute biliary obstruction
• In diseases of the liver parenchyma, ALT rises more prominently than AST.
• If AST > ALT, alcoholic hepatitis, toxic hepatitis, Wilson's disease and ischemic hepatitis should be considered first.
• Prevalence of AST in a chronic hepatitis patient with a previous high ALT indicates the development of fibrosis and progression to cirrhosis.
• The most common cause of aminotransferase elevation in the population is non-alcoholic fatty liver disease (NAFLD).
• AST and ALT levels do not correlate with severity of injury and prognosis in acute hepatitis.
Cholestasis Tests
• First of all, ALP (high sensitivity) is used for cholestasis screening.
• In patients with elevated ALP, GGT is often used to confirm whether it is of hepatic origin.
Alkaline Phosphatase (ALP):
• Its height can be caused by many organs and tissues (Hepatobiliary system pathologies, osteoblastic activity of the bone, placenta, etc.).
• Normal serum level is 30-140 IU/L.
GGT (Gamma-glutamyl transferase):
• Normal serum value is 0-45 U/L.
• While ALP is normal in alcoholics and Wilson's disease, GGT may be high.
• In normal pregnancy, GGT does not increase in serum, so it is more valuable than other enzymes in evaluating cholestatic conditions that occur during pregnancy.
Other cholestasis tests
5 nucleotidase, Leucine aminopeptidase
Tests to Measure the Synthesis Capacity of the Liver
Albumin:
• Its normal value is 3.5-5 g/dl and its half-life is 20 days.
• Since it has a long half-life, it cannot reflect the synthesis function well in acute liver diseases.
• In chronic liver diseases;
Albumin level drops
The level of globulin increases (polyclonal).
The albumin to globulin ratio is reversed.
Prothrombin Time (PTZ) / INR:
• The coagulation factor with the shortest half-life is Factor VII. It takes part in the extrinsic trough of coagulation.
• The extrinsic pathway is evaluated with PTZ (INR); It is the earliest indicator of hepatic synthesis dysfunction.
• Among the liver function tests, it is the test with the highest prognostic value showing acute liver damage.
• In cholestasis, Vit K absorption is affected and PTZ/INR is prolonged as the synthesis of Vit K dependent coagulation factors decreases. Intramuscular Vit K is administered to differentiate this condition; PTZ/INR returns to normal in cholestasis, but PTZ/INR elevation due to parenchymal liver disease does not return to normal.
