The liver is an organ weighing about 1.4 kg, located in the right upper abdomen, below the diaphragm. One of the key functions of the liver is detoxification – processing toxic substances such as alcohol and by-products from the breakdown of medications to be removed via the kidneys or eliminated with the faeces.
The liver is also responsible for the production of bile to break down nutrients, as well as controlling blood clotting, converting food to energy, storing it as glycogen, and storing fat-soluble vitamins such as D and E. Any damage to the liver may disturb its ability to function normally and over time, may result in scarring (cirrhosis), which may lead to liver failure.
What is a liver function test?
The term ‘liver function tests’ (also known as LFTs) refers to a simple blood test measuring markers in your blood to assess and monitor liver damage. So when you see the term ‘LFT’ on a blood test, it means your healthcare provider is checking on the health of your liver. This is one of the most commonly ordered blood tests in Australia.
What does ELFT or E/LFT on your blood test mean?
The E stands for electrolytes. Electrolytes may include tests such as sodium, potassium, chloride, bicarbonate, calcium and phosphate. These are vital to the processes in your body and can become unbalanced if you have been unwell or are dehydrated (for example, from vomiting or diarrhoea). If your levels are too low or too high, depending on the particular electrolyte, your doctor may prescribe treatment. Electrolytes are also used to assess the health of your kidneys. Their health is critical as one of their main jobs is to keep your electrolytes in balance regardless of what else is happening in your body.
Why would I need a liver function test?
LFTs may be performed for a variety of reasons, this could include if you have or are suspected of having liver injury. Your healthcare professional may recommend that you have the test if you have:
- Jaundice - yellow discolouration of your skin, the whites of your eyes and body fluids
- Suspected hepatitis – a viral infection causing inflammation and liver damage
- History of alcohol abuse
- A family history of a genetic liver condition – for example, haemochromatosis, a genetic disorder in which too much iron is taken into the body, potentially causing damage to the liver
- Illicit drug use - Chronic use of certain drugs may lead to significant injury to the liver
- An existing liver disease – such as liver cancer
- Been using medications that may cause damage to the liver – such as valproate or methotrexate, or paracetamol overdose
What does the test measure?
The tests measure the levels of certain enzymes and proteins in your blood, including:
Liver enzymes
These are proteins produced in the liver. The four common enzymes used to detect liver disease are:
- Aspartate transaminase (AST) – an enzyme found in the liver, heart, kidney and lungs
- Alkaline phosphatase (ALP) – a group of enzymes formed in the liver, bones, gut, skin and placenta
- Alanine transaminase (ALT) – an enzyme found in the liver in high concentrations
- Gamma-glutamyl transpeptidase (GGT) – another enzyme found in high amounts in the liver
Bilirubin
A yellow pigment compound formed from the breakdown of red blood cells and is carried in the bloodstream to the liver to be excreted in the bile. When the liver is damaged, bilirubin may accumulate in the blood and deposit in the skin, resulting in jaundice. High levels of bilirubin can be detected with a blood test.
Proteins
The test measures the levels of two main proteins that are produced in the liver: albumin and globulin.
Signs and symptoms of liver disease
Early liver disease may have minimal or no symptoms, but as the disease progresses, you may notice:
- Jaundice - a yellow tone to the skin and whites of eyes, and brownish urine
- Ascites - the abdomen becomes distended with fluid
- Vomiting blood or black stools – a result of ruptured blood vessels in the stomach and the oesophagus
The bottom line
Liver function tests are not used to diagnose specific liver diseases, nor can they assess the severity or progression of liver disease; they may, however, indicate that there is some problem with the liver or elsewhere in the body.
The results are usually evaluated together, and your healthcare professional may determine the need for further testing by looking at the pattern of the current and past results, as well as your current and past symptoms and lifestyle factors such as alcohol use and medications.
Related reads:
References
- Institute for Quality and Efficiency in Health Care (IQWiG). (2016, August 22). How does the liver work? InformedHealth.org - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK279393/
- Liver problems - Symptoms and causes - Mayo Clinic. (2023, June 21). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/liver-problems/symptoms-causes/syc-20374502
- Lala, V. (2023b, July 30). Liver function tests. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK482489/
- Sharma, A. (2023, July 3). Chronic liver disease. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK554597/
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