The Role of the Liver
The liver is arguably one of the most important organs in our bodies. It has many functions:
- Storing energy (fuel for the body) in the form of glycogen from carbohydrates and other sugars.
- Helping to process fats and proteins from digested food.
- Making proteins that help the blood to clot.
- Processing and eliminating many medicines to prevent toxicity.
- Helping to remove poisons, toxins, and drugs from the body.
- Making bile to help digest essential fats from the gut.
Without the liver, we cannot live; we cannot even replace it without another living liver – the brain is the only other organ about which that can be said. When it is functioning under par, or is damaged by disease or illness, our overall health can suffer. Knowing your liver is okay can be reassuring!*
Why Get This Test?
People usually get a liver function test to help diagnose certain liver conditions, such as:
- Hepatitis (infection and inflammation of the liver).
- Cirrhosis (scarring of the liver).
- Alcoholic liver disease (liver damage and the associated loss of function caused by excessive alcohol consumption).
What Is Tested In The “Liver Function Test”?
The term liver function test actually refers to lots of different tests. When doctors talk about your liver function, liver function tests, or LFTs, they are usually referring to a group of enzymes that the liver releases when it is damaged in some way. These are:
Alanine transaminase (ALT).
This enzyme helps to process proteins. It is found inside liver cells. When the liver is injured or inflamed, the blood level of ALT usually rises.
Aspartate aminotransferase (AST).
This is similar to ALT; however, AST can also be released if muscle (heart or skeletal) is damaged.
Alkaline phosphatase (ALP).
Unlike the ALT and AST enzymes, this is mainly present in the liver cells next to bile ducts. It is also present in bone.
Gamma-glutamyl transferase (GGT or ‘gamma GT’).
This enzyme is found in high quantities in the liver. Although it can be raised for many reasons, it is most commonly seen with heavy alcohol drinking.
This is made when haemoglobin is broken down in the liver. The liver cells take bilirubin and attach a sugar molecule to it, which makes it ‘conjugated’ bilirubin that can pass into the bile ducts, and then the gut. If your bilirubin increases you will turn yellow, which is medically called jaundice.
However, these are not “true” tests of liver function; they just tell us if there is liver damage or blockage. True tests of liver function look at the things that the liver makes. Therefore, a proper liver function test like ours will also look at the following:
This is the main protein made by the liver.
This measures the total albumin (the main protein made by the liver) and all other proteins in the blood. If you compare total protein to albumin, you can get a clearer picture of whether the liver is causing the problem.
Blood clotting tests.
Although it is possible to test for lots of different clotting disorders and problems, it is usually sufficient to assess the prothrombin time (PT), which is closely related to the liver’s production of clotting factors.
A comprehensive liver function test measures all of these factors. An abnormal result indicates a problem with the liver, and may help to identify the cause if reviewed by a medical professional. Although further tests may be needed to clarify the exact cause of the problem, knowing there is a problem is an important first step*. Additional tests need to be agreed between you and your doctor, but typically start with either a scan of the liver or a repeat blood test after 3 months.
What Will the Test Involve?
This test involves taking a small blood sample from a vein.
What Could Abnormal Results Mean?*
On its own, no test can provide a definitive diagnosis, and can only provide important “clues” about possible problems. Normal results cannot entirely exclude disease: for example, normal results can exist in patients with serious disease, and occasionally, abnormal results can arise without any health problems. The normal ranges of tests can also vary between different laboratories, so it is not always possible to compare results directly.
At Alpha Healthlabs, we believe in giving you an unparalleled and ethically sound service. Therefore, the meaning of all your results will be explained and we will suggest the most appropriate next course of action. It is important that you do not initiate any action based on these results without first consulting your General Practitioner.
Common Issues Raised by This Test
The common issues raised by this test include:
Raised alanine aminotransferase (ALT) and aspartate aminotransferase (AST)
This indicates leakage from liver cells due to either inflammation, damage, or cell death. Liver disease is more likely when both are raised together, with ALT being higher in early disease. ALT is more specific for liver disease because other tissue can release AST.
Raised gamma-glutamyl transferase (GGT)
This is more useful for detecting drug-related and alcohol-related liver damage.
Raised alkaline phosphatase (ALP)
This helps to tell if the liver problem is due to bile duct blockage and damage. Also, certain bone diseases can increase ALP, so it is important to interpret these results in the context of the other liver function tests, and with the assistance of your doctor.
Albumin levels are lowered in long-standing liver disease or other chronic conditions like malnutrition, kidney disease, and extensive inflammation in the body. Total protein is usually normal in liver disease.
A long prothrombin time (PT)
This suggests either a deficiency of the clotting factors made by the liver or a deficiency of vitamin K (which is needed for the factors to work). This is one of the reasons why people with liver disease are more prone to bruising.
Raised total bilirubin – conjugated or unconjugated
Total bilirubin increases due to liver disease or bile blockage. For example, gallstones or a tumour in the pancreas can prevent bilirubin getting to the gut, causing it to build up on “spill” into the blood. Also, hepatitis, liver injury, or long-term alcohol abuse can damage the liver enough for it to start “spilling” bilirubin into the blood. If either of these happens, you get a raised conjugated bilirubin.
If you have a non-liver related problem, you are more likely to get a raised ‘unconjugated’ bilirubin. Thus mainly happens when red blood cells are broken down very rapidly, in a condition called haemolytic anaemia.