Liver Function Tests (LFTs) are a group of blood tests that can help show how well your liver is working. They measure several substances made by the liver including enzymes and proteins. Each substance gives different information. Looked at together, along with your symptoms and medical history, they help build a picture of your liver’s health. Either higher or lower than normal levels of these substances can indicate a problem with your liver.
What is being tested?
Liver Function Tests (LFTs) is a group of tests that are performed together to detect, evaluate, and monitor liver disease or damage. The liver is one of the largest organs in the body and is located in the upper right-hand part of the abdomen and behind the lower ribs. The liver metabolises and detoxifies drugs and substances that are harmful to the body. It produces blood clotting factors, proteins, and enzymes, helps maintain hormone balances, and stores vitamins and minerals. Bile, a fluid produced by the liver, is transported through ducts directly to the small intestine to help digest fats or to the gallbladder to be stored and concentrated for later use.
A variety of diseases and infections can cause acute or chronic damage to the liver, causing inflammation, scarring, bile duct obstructions, clotting abnormalities, and liver dysfunction. Alcohol, drugs, some herbal supplements, and toxins can also pose a threat. A significant amount of liver damage may be present before symptoms such as jaundice, dark urine, light-coloured stools, pruritus, nausea, fatigue, diarrhoea, and unexplained weight loss or gain emerge. Early detection is essential in order to minimize damage and preserve liver function.
LFTs measure enzymes, proteins, and substances that are produced or excreted by the liver and are affected by liver injury. Some are released by damaged liver cells and some reflect a decrease in the liver's ability to perform one or more of its functions. When performed together, these tests give the doctor a snapshot of the health of the liver, an indication of the potential severity of any liver injury, change in liver status over time, and a starting place for further diagnostic testing.
How is it used?
Liver Function Tests (LFTs) may be used to screen a person for liver damage, especially someone who has a condition, or is taking a drug, that may affect the liver.
LFTs or one or more component tests may be used to help detect liver disease if a person has symptoms that indicate possible liver dysfunction or if a person is being monitored or treated for a known condition or liver disease. A bilirubin test, for instance, may be ordered to evaluate and monitor a jaundiced newborn.
Abnormal tests on a liver function tests panel may prompt a repeat analysis to see if the elevation or decrease persists and/or may indicate the need for additional testing to determine the cause of the liver dysfunction.
The group of tests may also be ordered to monitor liver function and the effectiveness of treatment in someone who has a liver disease.
When is it requested?
LFTs, or one or more components, may be ordered when someone is at risk for liver dysfunction. Some examples include:
people who have a history of known or possible exposure to hepatitis viruses
those who are heavy alcohol drinkers
individuals whose families have a history of liver disease
people who take drugs that might occasionally damage the liver
LFTs may be ordered when a person has signs and symptoms of liver disease. Some of these include:
Usually no one single set of liver tests are used to make a diagnosis. Often, several LFTs will be ordered over a few days or weeks to determine if a pattern is present and to help determine the cause of the liver disorder.
When liver disease is detected, it may be monitored on a regular basis over time with the LFTs or with one or more of its components. LFTs may also be ordered regularly to monitor the effectiveness of treatment for the liver disorder.
What does the result mean?
LFT results are not diagnostic of a specific condition; they indicate that there may be a problem with the liver. In a person who does not have symptoms or identifiable risk factors, abnormal liver test results may indicate a temporary liver injury or reflect something that is happening elsewhere in the body – such as in the skeletal muscles, pancreas, or heart. It may also indicate early liver disease and the need for further testing and/or periodic monitoring.
Results of LFTs are usually evaluated together. Several sets of results from tests performed over a few days or weeks are often assessed together to determine if a pattern is present. Each person will have a unique set of test results that will typically change over time. A doctor evaluates the combination of liver test results to gain clues about the underlying condition. Often, further testing is necessary to determine what is causing the liver damage and/or disease.
The table below shows examples of some combinations of results that may be seen in certain types of liver conditions or diseases.
|BILIRUBIN||ALT AND AST||ALP AND GGT||ALBUMIN||PT||TYPE OF LIVER CONDITION OR DISEASE|
|Normal or increased usually after ALT and AST are already increased||Usually greatly increased; ALT is usually higher than AST||Normal or only moderately increased||Normal||Usually normal||Acute liver damage (due, for example, to infection, toxins, or drugs etc)|
|Normal or increased||Moderately increased||Normal to slightly increased||Normal||Normal||Chronic forms of various liver disorders|
|Normal or increased||AST is normally higher than the level of ALT||Normal or moderately increased, GGT markedly increased||Normal||Normal||Alcoholic hepatitis|
|May be increased but this usually occurs later in the disease||AST is usually higher than ALT but levels are usually lower than in alcoholic disease||Normal or increased||Usually decreased||Usually prolonged||Cirrhosis|
|Normal or increased; increased in complete obstruction||Normal to moderately increased||Increased; often greater than 4 times what is normal||Usually normal but if the disease is chronic, levels may decrease||Usually normal||Bile duct obstruction, cholestasis|
|Usually normal||Normal or slightly increased||Usually greatly increased||Normal||Normal||Cancer that has spread to the liver (metastasised)|
|May be increased, especially if the disease has progressed||AST higher than ALT but levels lower than that seen in alcoholic disease||Normal or increased||Usually decreased||Usually prolonged||Cancer originating in the liver (hepatocellular carcinoma, HCC)|
|Normal or increased||Moderately increased||Normal or slightly increased||Normal or decreased||Normal||Autoimmune|
If a person is taking drugs that may affect their liver, then abnormal test results may indicate a need to re-evaluate the dosage or choice of medication. When a person with liver disease is being monitored, then the doctor will evaluate the results of the liver panel together to determine if liver function in worsening or improving. For example, increasingly abnormal bilirubin, albumin, and/or PT may indicate a deterioration in liver function, while stable or improving results of these tests may indicate liver function preservation or improvement.
Is there anything else I should know?
In order to diagnose a liver disease, a doctor will evaluate the liver panel test results, order follow-up tests such as hepatitis testing, and may order a liver biopsy and/or imaging scans to help confirm a diagnosis and determine the extent of liver damage.
Many over-the-counter drugs and herbal or dietary supplements have the potential to affect the liver. Excessive paracetamol use and the combination of paracetamol and alcohol for instance can cause severe liver damage, as can exposure to toxins such as poisonous mushrooms.
Yes, early liver disease often causes no symptoms or mild nonspecific symptoms, such as fatigue and nausea.
Yes, many temporary conditions, such as shock, burns, severe infections, muscle trauma, dehydration, pancreatitis, haemolysis, and pregnancy can cause one or more of the liver function tests to be abnormal.
Some liver conditions, such as haemochromatosis and Wilson's disease, may be inherited. Early detection of these conditions allows them to be treated and managed appropriately.
Depending on the results of the liver panel and other factors such as signs, symptoms and clinical and family history, a doctor may suspect a particular cause of liver disorder and order follow-up tests. Some examples include:
|Suspected type of liver disorder||Other or follow- up tests|
|Viral infection||Hepatitis A, B or C|
|Alcohol abuse/ hepatitis||Ethanol|
|Toxic or drug-induced||Tests for toxins, drugs including drugs of abuse screen|
|Wilson's disease||Copper, Caeruloplasmin|
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