Understanding Liver Function Tests: Purpose, Types & Interpretation

The Liver is responsible for hundreds of vital functions in the body, including aiding in digestion of food, eliminating bodily waste products and producing clotting factors. Having said that, abnormal functioning of the liver can lead to a variety of health concerns, from abdominal pain to even liver diseases. A great indicator of the functionality of the liver is the liver function tests. These can help you understand how well the liver is functioning and avoid any long term complications, making it crucial to get this test done periodically. This blog will brief you on the topic of liver function tests including its purpose, types, and interpretation. 

What is a Liver Function Test / LFT Test?

Liver function tests (LFTs) are a set of blood tests used to assess the health and functionality of the liver. These tests measure various enzymes, proteins, and substances that the liver produces or processes. By evaluating these components, LFTs can help determine if the liver is functioning properly and identify any potential liver damage or disease.

An LFT test typically includes measurements of:

Enzymes: These are proteins that speed up chemical reactions in the body. Elevated liver enzymes causes liver damage or inflammation.

Proteins: The liver produces several important proteins, including albumin. Measuring these proteins helps assess the liver's ability to perform its normal functions.

Bilirubin: This substance is produced when the liver breaks down old red blood cells. High levels of bilirubin can indicate a problem with the liver's ability to process and clear this waste product.

PROTHROMBIN TIME (INR): Helps in assessing coagulation and synthetic function of liver. 

Why is a Liver Function Test Necessary?

Liver profile tests are necessary for several important reasons:

Diagnosing Liver Diseases: LFT blood test can help diagnose various liver conditions, such as hepatitis, fatty liver disease, cirrhosis, and liver cancer. Early detection is crucial for effective treatment and management of these diseases.

Monitoring Liver Health: For individuals with known liver conditions, LFTs are essential for monitoring the progression of the disease and the effectiveness of treatments. This helps in making necessary adjustments to therapy and preventing complications.

Evaluating Symptoms: When patients present with symptoms like jaundice, abdominal pain, or unexplained weight loss, LFTs can help determine if these symptoms are related to liver dysfunction.

Guiding Treatment Decisions: LFT results can inform healthcare providers about the severity of liver damage, which is crucial for deciding the best course of treatment. This includes decisions about medication dosage, the need for liver transplantation, or other therapeutic interventions.

Assessing Overall Health: The liver plays a vital role in many bodily functions, including metabolism, detoxification, and blood clotting. LFTs provide insight into overall health and can reveal issues that might not be apparent through symptoms alone.

Screening for Liver Damage: People who are at risk for liver disease, such as those with a history of heavy alcohol use, viral hepatitis, or certain genetic conditions, benefit from regular LFTs to detect early signs of liver damage.

Evaluating Medication Effects: Some medications can have hepatotoxic effects, meaning they can cause liver damage. Regular LFTs are necessary for patients taking such medications to ensure their liver remains healthy.

What are the Different Types of Liver Function Tests? 

Liver function tests encompass a variety of individual tests that measure different aspects of liver health. Here are some of the key types:

Alanine transaminase (ALT) Test

The ALT test measures the level of alanine transaminase, an enzyme primarily found in the liver. Elevated ALT levels can indicate liver damage or inflammation, as ALT is released into the bloodstream when liver cells are damaged.

Aspartate Aminotransferase (AST) Test

The AST test measures the level of aspartate aminotransferase, an enzyme found in various organs, including the liver. Like ALT, elevated AST levels can suggest liver damage, but AST is not as specific to the liver as ALT, as it is also present in the heart and muscles.

Alkaline Phosphatase (ALP) Test

The ALP test measures the level of alkaline phosphatase, an enzyme related to the bile ducts. High levels of ALP can indicate bile duct obstruction, liver inflammation, or bone disease.

Albumin Test - Bilirubin Test

The albumin test measures the level of albumin, a protein produced by the liver. Low levels of albumin can suggest liver disease or other conditions affecting the liver's ability to produce proteins.

The bilirubin test measures the level of bilirubin, a by-product of red blood cell breakdown processed by the liver. High levels of bilirubin can lead to jaundice and indicate liver dysfunction or bile duct problems.

International Normalised Ratio (INR)

The INR test measures the time it takes for blood to clot and compares it to a standard value. The liver produces clotting factors, so an abnormal INR can indicate liver dysfunction. This test is crucial for monitoring patients on anticoagulant therapy and assessing liver function in chronic liver disease.

Alpha-fetoprotein Test 

The AFP test measures the level of alpha-fetoprotein, a protein produced by the liver. Elevated AFP levels can be a marker for liver cancer or other liver diseases. This test is often used in conjunction with imaging studies for diagnosing and monitoring liver cancer.

Mitochondrial Antibodies Test

The mitochondrial antibodies test detects the presence of antibodies against mitochondria, which can indicate autoimmune liver diseases such as primary biliary cholangitis (PBC). This test helps diagnose and monitor autoimmune liver conditions.

Normal Ranges of LFT Tests

These are general ranges and may vary depending on the laboratory, age, sex, and other factors. Your doctor will interpret your specific test results in the context of your medical history and overall health.

How to Interpret the Results of a Liver Function Test?

Interpreting liver function test (LFT) results can get complex, as different tests assess various aspects of liver function. While this blog provides a general overview, it's crucial to remember that your doctor is best suited to interpret your individual results in the context of your medical history and overall health.

Here's a breakdown of how we can generally approach interpreting some common liver function test result:

Enzyme Levels

ALT (Alanine aminotransferase) and AST (Aspartate aminotransferase): These enzymes are present in the liver cells. When the liver is damaged, they leak into the bloodstream, raising their levels. Elevated levels can indicate liver injury, inflammation, or disease. The degree and pattern of elevation can also provide clues to the cause. For instance, if ALT is significantly higher than AST, it often suggests liver-specific damage.

Bilirubin Levels

Bilirubin is a waste product produced by the breakdown of red blood cells. The liver normally removes bilirubin from the blood. High bilirubin levels (hyperbilirubinemia) can indicate-

Liver damage: If the liver is unable to process bilirubin efficiently.

Bile duct blockage: If bilirubin can't drain out of the liver due to a blocked bile duct.

Increased red blood cell breakdown: From conditions like hemolytic anaemia.

Other Test Results

Albumin: Produced by the liver, low albumin levels may indicate liver damage or malnutrition.

Alkaline Phosphatase (ALP): Elevated ALP can suggest liver problems, bone disease, or bile duct blockage.

INR (International Normalised Ratio): An abnormal INR may indicate liver damage or vitamin K deficiency, as the liver produces clotting factors.

Alpha-Fetoprotein (AFP): Primarily used for cancer screening, elevated AFP levels can be associated with liver cancer.

Mitochondrial Antibodies Test: Positive results may suggest autoimmune liver disease.

How is a Liver Function Test Performed?

A liver function test is a simple blood test. Here's a breakdown of the process:

Preparation: You may receive instructions from your doctor regarding fasting beforehand, especially for certain tests. In general, you can drink water before the test.

Blood Draw: A healthcare professional will locate a vein in your arm, typically at the bend of your elbow. They will then insert a thin needle and collect a small amount of blood into a vial or test tube.

Sample Processing: The blood sample is sent to a laboratory for analysis.

Results: You will receive the results of your LFTs within a few days, depending on the lab. Your doctor will interpret the results in the context of your medical history and discuss them with you.

The entire procedure for the blood draw typically takes less than five minutes and is minimally invasive.

Conclusion

LFTs offer a window into your liver's health, potentially detecting issues early and promoting better outcomes. By understanding these tests and working with your doctor, you can take charge of your liver health. If you're looking for experienced professionals to guide you through liver health management, Max Hospital has a team of specialists that are ready to answer your questions and provide comprehensive care. Schedule an appointment today and take the first step towards optimal liver health.