Liver Function Testing

Bile acids are synthesised in the liver and stored in the gallbladder. When food is consumed bile acids are secreted into the intestine where they facilitate the formation of micelles and promote processing of dietary fat.

Bile Acids Testing can aid diagnosis of cholestasis, portosystemic shunt and bile acids malabsorption.

Raised Bile Acids in pregnancy are indicative of Obstetric Cholestasis, a condition that is associated with foetal distress, premature labour and still birth. Determination of bile acids can also assist with the diagnosis of other liver diseases and bile acid malabsorption. Increased bile acids in fasting or postprandial state are considered a specific indicator of liver disease and decreased levels are associated with bile acid malabsorption.

Bilirubin is a product of haem catabolism. Small amounts of bilirubin are present in the blood as a result of damaged and dead red blood cells which are disposed of via the spleen. When too many cells are being destroyed or the liver is unable to remove all of the bilirubin from the blood the levels of bilirubin increase and can result in jaundice.

New born babies lack the intestinal bacteria that help process bilirubin and neonatal bilirubineamia is not uncommon. Typically this resolves itself in a couple of days, but in some instances the newborn's blood may have been destroyed because of blood typing incompatibilities or other genetic factors. It is important that the levels of bilirubin do not get too high in young babies as excessive bilirubin damages developing brain cells and can cause mental retardation, physical abnormalities or blindness.

There are a number of diseases that can result in liver fibrosis such as viral hepatitis, alcoholism, fatty liver disease or genetic disorders. Fibrotic injury distorts the normal liver architecture and can result in organ dysfunction and hypertension. Fibrosis can progress to cirrhosis and also lead to hepatocellular carcinoma (HCC). Serum Hyaluronic Acid measurement can assist in diagnosis and monitoring of liver fibrosis and cirrhosis.

Hyaluronic Acid is a polysaccharide produced by fibroblasts throughout the body and plays a structural role in the connective tissue matrix. Whilst high concentrations of HA may be found in connective tissues and joints, serum levels of HA are typically low in healthy individuals as circulating HA is rapidly removed from the blood by sinusoidal endothelial cells (SECs) in the liver. The HA binds to cell surface receptors and is then endocytosed (internalized) by the cell and degraded. A strong correlation is seen between serum HA and liver pathology, particularly in cirrhosis, where a reduction in HA receptors on the SECs reduces the rate at which HA can be removed resulting in an increase in circulating HA.

Alanine aminotransferase (ALT) and Aspartate Aminotransferase (AST) are the most important representatives of a group of enzymes which catalyse the conversion of alpha-keto acids into amino acids by transfer of amino groups.

Alanine aminotransferase is an enzyme found predominantly in the liver but smaller amounts are also found in the kidneys, heart and muscles. Under normal conditions levels of ALT in the blood are low but when the liver is damaged ALT is released into the blood stream and can usually be detected before other symptoms of liver damage such as jaundice occur. Serum ALT, sometimes known as serum glutamic-pyruvic transaminase (SGPT) can help with the diagnosis and monitoring of liver disorders.

Aspartate Aminotransferase (AST) is an enzyme found predominantly in heart and liver and to a lesser extent in other muscles. Measuring serum Aspartate Aminotransferase (AST) also known as serum glutamic-oxalacetic transaminase (SGOT) can be assistance when diagnosing liver disorders and may also be indicative of myocardial infarction, myscle dystrophy or organ damage.

Aminotransferase enzymes can indicate the degree of liver inflammation and elevated levels are seen in hepatitis. ALT and AST are usually measured together as different ratios of AST:ALT are associated with Wilsons disease, alcoholic liver disease and non alcoholic steatohepatitis.

Alkaline Phosphatase (ALP) is an enzyme found in the liver and biliary tract. Enzyme levels are dependent upon age and sex and increase during bone growth in childhood and in pregnancy. Pathological increases in ALP activity is observed in hepatitis, cirrhosis, malignant tumours and bone diseases. ALP may be of interest to those investigating reproduction, child development, liver disease, bone disease or cancer.

Gamma GT (gamma glutamyltransferase) (GGT) is an enzyme found in high concentrations in renal tissue. In patients with hepatobiliary diseases significant levels of Gamma GT are found in the serum. This hepatic enzyme appears sooner than other enzymes and remains in the plasma for a longer time making its measurement a valuable tool in the diagnosis of such diseases.

ALP and GGT are often measured together and increases in both of these enzymes are seen in cases of obstructive of cholestatic liver disease where bile is not properly transported from the liver due to a blockage of the bile ducts. Measuring an increase in GGT will also help to confirm that the rise in serum ALP originates from liver injury.Bilirubin for Neonatal Jaundice

Bilirubin is a product of haem catabolism. Small amounts of bilirubin are present in the blood as a result of damaged and dead red blood cells which are disposed of via the spleen. When too many cells are being destroyed or the liver is unable to remove all of the bilirubin from the blood the levels of bilirubin increase and can result in jaundice.

New born babies lack the intestinal bacteria that help process bilirubin and neonatal bilirubineamia is not uncommon. Typically this resolves itself in a couple of days, but in some instances the newborn's blood may have been destroyed because of blood typing incompatibilities or other genetic factors. It is important that the levels of bilirubin do not get too high in young babies as excessive bilirubin damages developing brain cells and can cause mental retardation, physical abnormalities or blindness.