Liver is the second largest organ in the body, and it plays a vital role in maintaining the body’s overall health. It is called the ‘chemical factory’ of the body as the liver produces several chemicals, take part in about 500 chemical reactions occurring in the body, and also breaks down the harmful chemicals into harmless ones.
Functions of the Liver
Although the liver performs several functions in the body, the major ones are listed below:
- Produces bile that breaks down fat for use as energy, and helps remove toxins
- Stores extra iron
- roduces albumin and other proteins essential for body functions
- Produces cholesterol and other essential fatty acids
- Stores glucose as glycogen for use as needed
- Converts harmful ammonia to harmless urea
- Breaks down medications consumed or its target use
- Promotes absorption of nutrients in the gut and its metabolism
Our busy lifestyles that involves, sedentary lives and consumption of junk and processed food, can put a lot of strain on our liver, so it is important to get tested for liver disease. Liver Function Tests (LFTs) are simple blood tests to help diagnose and monitor liver diseases like hepatitis or liver damage.
Liver function test parameters and their interpretation
A liver panel includes the following tests:
1. Aspartate aminotransferase (AST): AST is an enzyme that is found mostly in the cells of the liver and helps in metabolizing amino acids. AST levels are not as specific for liver damage compared to ALT therefore it is usually measured together with ALT to check for liver problems. This blood test is also known as SGOT test.
- When the liver is damaged, AST can be released into the bloodstream. A high test result on an AST test may be due to liver or muscles problem.
- The normal range for AST in adults is typically 15 - 46 U/L.
- When the liver is damaged due to alcohol consumption, AST level often increases much more than ALT.
- levated AST without elevated ALT may indicate heart or muscle disease.
2. Alanine aminotransferase (ALT): ALT is another enzyme that helps break down proteins and is found primarily in the liver. This blood test is also known as SGPT test.
- ALT levels in the blood are low in healthy individuals. Normal liver function range for ALT is 13 - 69 U/L.
- When the liver is damaged, ALT is usually released into the blood as seen in the case of jaundice.
- People having blocked bile ducts, cirrhosis, and liver cancer may have moderately elevated or close to normal ALT levels.
- A higher ALT test result can be a sign of liver damage (acute hepatitis). Very high levels are found in conditions like viral hepatitis, ischemic hepatitis, liver damage due to drugs.
3. Alkaline phosphatase (ALP): ALP is an enzyme found in liver, bile ducts, and bone. ALP is necessary to help digest fat present in the diet.
- The normal range for ALP in adults is 38 - 126 U/L.
- ALP blood levels can greatly increase, if you have liver damage or disease, a blocked bile duct, bone disease, inflammation of the gallbladder (cholecystitis) or gallstones.
- Small increase of the blood ALP level is seen in the case of liver cancer and cirrhosis, with the use of certain drugs, and in hepatitis. Pregnancy can also raise ALP levels.
4. Bilirubin: Bilirubin is produced during normal break down of red blood cells. Normally, the liver cleans up the bilirubin in your body. Higher than normal levels of bilirubin may indicate liver damage or disease (jaundice).
- Two types of bilirubin measured include direct and indirect bilirubin. Normal results for a total bilirubin test are 0.0-1.1 mg/dL for adults.
- Higher than normal levels of direct bilirubin in your blood is indicative of your liver not being able to clear bilirubin from the body properly.
- Elevated levels of indirect bilirubin may indicate an increased breakdown of red blood cells or an inability of the liver to process bilirubin.
5. Albumin and total protein: Albumin is one of the many proteins made in the liver. Your body uses this protein to fight infections and to perform other functions. Lower than normal levels of albumin and total protein is indicative of liver damage or disease. Normal range in adults for albumin is 3.5 - 5.0 g/L and total serum protein is 5.5 - 8.0 g/L.
Total protein levels may decrease in the following instances:
- Interference with the production of albumin or globulin proteins, such as malnutrition or severe liver disease.
- Increased breakdown or loss of protein, such as kidney disease (nephrotic syndrome).
- Increased volume of plasma, the colourless liquid part of the blood (diluting the blood), such as congestive heart failure.
- Malabsorption (small intestine unable to absorb sufficient nutrients) is seen in inflammatory bowel disease.
6. Gamma-glutamyl transferase (GGT): It is an enzyme found in liver cells and this test used together with ALP test to determine the cause of increased ALP levels, either from bone or liver.
- A normal range for GGT levels in adults is 9 - 48 U/L.
- An increased GGT level is seen in the case of liver diseases, although the highest elevations are seen because of a blockage in the exit route of the liver.
- Elevated values can also indicate alcoholic liver damage.
- Increased GGT level is also seen due to certain medication mediated liver damage.
- Both ALP and GGT are elevated in the bile duct and liver disease, but only ALP will be elevated in bone disease.
7. L-lactate dehydrogenase (LD): LD is an enzyme in the liver. It plays an important role in making energy for your body.
- The normal range for LD levels for adults in the blood is 100-280 U/L.
- Elevated values LD values may indicate liver damage but can be elevated in many other diseases.
8. Prothrombin time (PT): PT is known as the time taken by your blood to clot. The liver produces most of the clotting proteins needed for blood to clot.
The normal range for PT results not on blood thinning medicines is:
- 11 - 13.5 seconds
- International Normalised Ratio (INR) of 0.8 - 1.1
- INR of 2.0 - 3.0
- Severe liver injury leads to reduced liver synthesis of clotting factors resulting in prolonged PT.
- Prolonged PT (or INR) may be caused due to other non-hepatic causes such as vitamin K deficiency, malabsorption, and genetic clotting disorders.
- Increased PT may indicate liver damage but can also be elevated if you're taking certain blood-thinning drugs.
LFTs are recommended when a person has signs and symptoms of liver disease or an infection such as jaundice, gastrointestinal issues, dark-coloured urine, fatigue, swelling in the legs/ ankles and a family history of liver disease. LFT test results are not diagnostic of a specific condition and are indicative of a problem with the liver. Get your liver function test to evaluate the health of your liver.
