Tests for liver disease.
Tests For Liver Function
Total Bilirubin – Normal range is 3 – 18 umol/L (0.174 – 1.04mg/dL).
AST – (aspartate aminotransferase) which was previously called SGOT. This enzyme can also be elevated in heart and muscular diseases and is not liver specific. Normal range of AST is 5-45 U/L.
ALT – (alanine aminotransferase) which was previously called SGPT and is more specific for liver damage. Normal range of ALT is 5-45 U/L.
AP – (alkaline phosphatase) is elevated in many types of liver disease but also in non-liver related diseases. Normal range of AP is 30-120 U/L.
GGT – (gamma glutamyl transpeptidase) is often elevated in those who use alcohol or other liver toxic substances to excess. Normal range of GGT is 5- 35 U/L.
What is a Liver Function Test?
How reliable is this test?
How do the cell membranes get damaged in the first place?
A Typical Liver Function Test
Result Unit Reference
- Bilirubin mg/dL (0.18 to 1.0)
- AP (Alk Phos) U/L (30 to 120)
- GGT (Gamma GT) U/L (5 to 35)
- LD Lactate Dehydrogenase U/L (100-225)
- AST (Aspartate aminotransferase) U/L (5 to 45)
- ALT (Alanine aminotransferase) U/L (5 to 45)
- Albumin g/L (38-55)
- Clotting Studies (Prothrombin Time) Seconds (11 to 13.5)
Alanine aminotransferase (ALT)
ALT was previously known as SGPT. The ALT is an enzyme that is produced in the liver cells (hepatocytes), therefore it is more specific for liver disease than some of the other enzymes . It is generally increased in situations where there is damage to the liver cell membranes. All types of liver inflammation can cause raised ALT. Liver inflammation can be caused by fatty infiltration (see fatty liver) some drugs/medications, alcohol, liver and bile duct disease.
Aspartate aminotransferase (AST)
Alkaline phosphatase is an enzyme, or more precisely a family of related enzymes, that is produced in the bile ducts and sinusoidal membranes of the liver but is also present in many other tissues. An elevation in the level of serum alkaline phosphatase is present in bile duct blockage from any cause. Therefore raised AP in isolation will generally lead a physician to further investigate this area. Conditions such as Primary Biliary Cirrhosis and Sclerosing Cholangitis will generally show a raised AP. Raised levels may also occur in cirrhosis and liver cancer. Alkaline phosphatase is also produced in bone, and if increased can indicate a bone disorder.
An enzyme produced in many tissues as well as the liver. Like alkaline phosphatase, it may be elevated in the serum of patients with bile duct diseases. Elevations in serum GGT, especially along with elevations in alkaline phosphatase, suggest bile duct disease. Measurement of GGT is an extremely sensitive test, however, and it may be elevated in virtually any liver disease and even sometimes in normal individuals. GGT is also induced by many drugs, including alcohol, therefore often when the AP is normal a raised GGT can often (but not always) indicate alcohol use. Raised GGT can often be seen in cases of fatty liver and also where the patient consumes large amounts of Aspartame (artificial sweetener) in diet drinks for example.
Bilirubin is the major breakdown product that results from the destruction of old red blood cells (as well as some other sources). It is removed from the blood by the liver, chemically modified by a process call conjugation, secreted into the bile, passed into the intestine and to some extent reabsorbed from the intestine. It is basically the pigment that gives faeces its brown colour. Bilirubin concentrations are elevated in the blood either by increased production, decreased uptake by the liver, decreased conjugation, decreased secretion from the liver or blockage of the bile ducts. In cases of increased production, decreased liver uptake or decreased conjugation, the unconjugated or so-called indirect bilirubin will be primarily elevated. In cases of decreased secretion from the liver or bile duct obstruction, the conjugated or so-called direct bilirubin will be primarily elevated. Many different liver diseases, as well as conditions other than liver diseases (e. g. increased production by enhanced red blood cell destruction), can cause the serum bilirubin concentration to be elevated. Most adult acquired liver diseases cause impairment in bilirubin secretion from liver cells that cause the direct bilirubin to be elevated in the blood. In chronic, acquired liver diseases, the serum bilirubin concentration is usually normal until a significant amount of liver damage has occurred and cirrhosis is present. In acute liver disease, the bilirubin is usually increased relative to the severity of the acute process. In bile duct obstruction, or diseases of the bile ducts such as primary biliary cirrhosis or sclerosing cholangitis, the alkaline phosphatase and GGT activities are often elevated along with the direct bilirubin concentration. (See Gilbert's Syndrome)
Albumin is the major protein that circulates in the bloodstream. As it is made by the liver and secreted into the blood it is a sensitive marker and a valuable guide to the severity of liver disease. Low serum albumin concentrations indicate the liver is not synthesizing the protein and is therefore not functioning properly. The serum albumin concentration is usually normal in chronic liver diseases until cirrhosis and significant liver damage is present. There are many other proteins synthesized by the liver, however the albumin is easily, reliably and inexpensively measured.
Platelets are cells that form the primary mechanism in blood clots. They're also the smallest of blood cells. They're derived from the bone marrow from the larger cells known as megakaryocytes. Individuals with liver disease develop a large spleen. As this process occurs platelets are trapped within the sinusoids (small pathways within the spleen) of the spleen. While the trapping of platelets is a normal function for the spleen, in liver disease it becomes exaggerated because of the enlarged spleen (splenomegaly). Subsequently, the platelet count may become diminished.
Prothrombin time (Clotting Studies)
The prothrombin time is tested to evaluate disorders of blood clotting, usually bleeding. It is a broad screening test for many types of bleeding disorders. When the liver is damaged it may fail to produce blood clotting factors
What is a Biopsy?
This procedure involves using a special needle to remove tissue from the liver to be examined in the laboratory. This will be used to assess the extent of scarring, fatty infiltration or liver damage. For the biopsy, you will lie on a hospital bed on your back or turned slightly to the left side, with your right hand above your head. After marking the outline of your liver and injecting a local anesthetic to numb the area, the physician will make a small incision in your right side near your rib cage, then insert the biopsy needle and retrieve a sample of liver tissue. In some cases, the physician may use an ultrasound image of the liver to help guide the needle to a specific spot.
How accurate is this test?
It is still regarded as the most accurate way of assessing the extent of damage to the liver. You will need to hold very still so that the physician does not nick the lung or gallbladder, which are close to the liver. The physician will ask you to hold your breath for 5 to 10 seconds while he or she puts the needle in your liver. You may feel a dull pain. The entire procedure takes about 20 minutes.
Who should NOT have this procedure done?
What is an ultrasound or sonograph?
This is a non invasive method of assessing liver health. It is an imaging procedure of the internal organs of the abdomen, including the liver, gallbladder, spleen, pancreas and kidneys. The ultrasound machine sends out high-frequency sound waves, which reflect off body structures to create a picture. There is no ionizing radiation exposure with this test. There are many reasons for performing an abdominal ultrasound including looking for a cause of pain, for stones in the gallbladder or kidney, or for a cause for enlargement of an abdominal organ. The reason for the examination will depend on your symptoms.
Functional Tests of the Liver
Recently tests that assess the liver’s function, especially its detoxification abilities, have become available. These tests are called Functional Liver Challenge Tests or a Functional Liver Detoxification Profile. During these tests the liver is challenged with caffeine, aspirin and paracetamol in safe oral doses. Samples of urine and saliva are then collected at timed intervals and sent to the laboratory where their levels of the excreted forms of these drugs are measured. These tests are non-invasive and assess the ability of the liver to detoxify and eliminate drugs and other chemicals. These tests are unique in that they assess the functional capacity of the liver in both phase one and phase two detoxification pathways. They can be conducted in the patient’s home and are simple to perform. Your health care practitioner can arrange them for you.