What Are Liver Function Tests (LFTs)?
Liver function tests (LFTs) are blood tests to assess how well the liver works.
These tests measure various substances in the blood that the liver produces or processes. The results provide essential information about the overall health of the liver and can indicate whether it is functioning normally or if there are any issues.
The liver performs a wide variety of critical functions. It processes nutrients absorbed by the intestines, detoxifies harmful substances, produces vital proteins like albumin, and produces bile to aid in digestion.
When the liver is not working optimally due to conditions like liver disease, inflammation, or damage, these substances can build up or be depleted, causing abnormal test results.
A typical liver function test panel may include several tests, which provide a comprehensive picture of liver health. These tests focus on liver enzymes, proteins, and byproducts that the liver produces, all of which can help identify liver problems at an early stage.
Why Are Liver Function Tests Important?
Liver function tests are vital for several reasons. They allow doctors to:
- Detect Liver Disease Early: Many liver diseases, including fatty liver, hepatitis, and cirrhosis, do not present clear symptoms in their early stages. Regular testing can detect these conditions before they become serious.
- Monitor Chronic Liver Conditions: If you have been diagnosed with a liver condition, such as hepatitis or cirrhosis, your doctor may order periodic liver function tests to monitor how the disease is progressing or how well a treatment is working.
- Assess the Effects of Medications: Some medications can cause liver damage over time. Liver function tests help monitor any adverse effects of drugs on liver function, especially when taking long-term medications.
- Evaluate Symptoms: Symptoms like jaundice (yellowing of the skin and eyes), abdominal pain, fatigue, or unexplained weight loss may indicate liver dysfunction. Liver function tests can help determine whether liver problems are causing these symptoms.
- Guide Treatment Decisions: If liver dysfunction is identified, these tests can help guide treatment plans, ranging from lifestyle modifications to medications, and even liver transplantation if necessary.
What Are the Common Liver Function Tests?
Liver function tests measure a variety of enzymes, proteins, and other substances in the blood to assess liver health. The most common tests in a liver panel include:
Liver Enzyme Tests
The liver produces enzymes that help break down proteins and other substances. When the liver is injured, these enzymes can leak into the bloodstream, leading to elevated levels. The main liver enzymes that are measured during liver function tests are:
- Alanine Transaminase (ALT): ALT is an enzyme produced mainly in the liver. It is released into the bloodstream when liver cells are damaged. High ALT levels are commonly associated with liver inflammation, such as hepatitis, or liver damage due to alcohol or drugs.
- Aspartate Aminotransferase (AST): AST is another enzyme found in the liver as well as in other organs like the heart, muscles, and kidneys. Elevated AST levels are often seen in liver damage, but high levels may also indicate issues with the heart or muscles. It is often measured alongside ALT to determine the cause of liver damage.
- Alkaline Phosphatase (ALP): ALP is an enzyme that is primarily found in the liver, bile ducts, and bones. High ALP levels can indicate liver disease related to bile duct blockages, such as cholestasis, or bone disease. It is also used to monitor conditions like primary biliary cirrhosis and biliary obstruction.
- Gamma-Glutamyl Transferase (GGT): GGT is an enzyme involved in detoxification. Elevated GGT levels often indicate liver disease, especially when there are bile duct problems or excessive alcohol consumption.
Bilirubin Test
Bilirubin is a waste product that is produced when the liver breaks down old red blood cells. The liver processes and excretes bilirubin in bile. If the liver is not functioning properly, bilirubin can build up in the bloodstream, leading to jaundice, and a yellowish discoloration of the skin and eyes. The bilirubin test measures both direct (conjugated) and indirect (unconjugated) bilirubin levels in the blood. Abnormal levels can indicate liver dysfunction or bile duct obstruction.
Albumin and Total Protein Tests
Albumin is the most abundant protein produced by the liver. It helps maintain blood volume and pressure by drawing water into the bloodstream. A total protein test measures all proteins in the blood, including albumin and globulins. Low levels of albumin or total protein can indicate liver disease or other conditions affecting protein production, such as malnutrition or kidney disease.
Prothrombin Time (PT) Test
The PT test measures how long it takes for your blood to clot. The liver produces several clotting factors necessary for blood coagulation. If the liver is damaged, it may not produce enough of these factors, resulting in prolonged clotting time. A prolonged PT may indicate liver dysfunction, cirrhosis, or liver failure.
Lactate Dehydrogenase (LDH) Test
LDH is an enzyme found in many organs, including the liver. Elevated LDH levels can indicate liver damage, but they can also be elevated due to damage in other organs, such as the heart or muscles. It is often used in conjunction with other liver tests to identify the source of damage.
When Are Liver Function Tests Performed?
Liver function tests are performed for various reasons, including:
Routine Screening
Liver function tests may be part of a regular health checkup, especially if you have risk factors for liver disease such as obesity, diabetes, or a history of alcohol abuse. Early detection of liver problems can prevent severe complications later on.
Monitoring Existing Liver Conditions
If you have already been diagnosed with a liver condition, such as hepatitis, fatty liver disease, or cirrhosis, your doctor will likely order regular liver function tests to monitor the progression of the disease and assess the effectiveness of treatments.
Assessing Medications
Certain medications can cause liver damage over time. Liver function tests are commonly used to monitor the effects of drugs. If you are on long-term medications, periodic liver tests may be recommended to ensure that your liver is functioning well.
Investigating Symptoms
If you experience unexplained symptoms such as jaundice, fatigue, abdominal pain, swelling, or dark urine, your doctor may order liver function tests to investigate the possibility of liver disease. These tests help confirm whether liver dysfunction is the cause of your symptoms.
How Are Liver Function Tests Performed?
Liver function tests are usually conducted by taking a small blood sample from a vein in your arm. The procedure is quick, generally painless, and involves minimal discomfort. Here’s what you can expect during the test:
Before the Test
In most cases, you don’t need to make any special preparations for liver function tests. However, your doctor may advise you to fast for 8–12 hours before the test, especially if other tests are being done in conjunction with the LFT. Make sure to inform your healthcare provider about any medications you are taking, as certain drugs can affect liver function results.
During the Test
Doctor will clean the area on your arm where the needle will be inserted. After locating a vein, they will insert a small needle to collect blood, which takes only a few minutes. Some people may feel a brief sting or discomfort during the blood draw, but the procedure is generally quick and well-tolerated.
After the Test
Once your blood sample is collected, it will be sent to a laboratory for analysis. Depending on the lab, you may receive results within a few hours or a few days. After the test, you can resume your normal activities, and there are typically no restrictions. Some people may experience mild bruising or soreness at the site where the blood was drawn, but this usually goes away within a few days.
How Do You Interpret Liver Function Test Results?
Once your liver function test results are available, your healthcare provider will review the findings and interpret them based on normal reference ranges. Here’s an overview of what high or low levels of certain tests might indicate:
Elevated ALT and AST
Elevated ALT and AST levels often indicate liver injury. High ALT levels are typically associated with liver inflammation or damage, while elevated AST levels may suggest liver problems or issues with other organs like the heart or muscles. If both ALT and AST are elevated equally, it suggests liver inflammation due to viral hepatitis or nonalcoholic fatty liver disease. If AST is much higher than ALT, it may indicate alcohol-related liver damage.
Elevated ALP and GGT
High ALP and GGT levels are often seen in bile duct diseases, such as cholestasis, bile duct obstructions, or primary biliary cirrhosis. Elevated GGT levels may also suggest excessive alcohol consumption or drug-induced liver damage.
High Bilirubin
Elevated bilirubin levels typically suggest liver dysfunction, as the liver is responsible for processing and excreting bilirubin. High levels of bilirubin may indicate hepatitis, cirrhosis, or bile duct obstructions.
Low Albumin or Total Protein
Low albumin or total protein levels may point to liver disease, as the liver is responsible for producing these proteins. Other conditions like malnutrition, kidney disease, or inflammatory disorders can also cause low protein levels.
Prolonged PT
A prolonged PT test indicates that the liver is not producing enough clotting factors, which could be due to cirrhosis or liver disease. A normal PT suggests that the liver is functioning properly.
Conclusion
Liver function tests are essential for monitoring liver health, diagnosing potential liver diseases, and assessing the effectiveness of treatments. Early detection of liver problems through routine testing can help prevent complications and ensure better health outcomes.
At Reeshitha Diagnostics Centre, we are committed to providing accurate, reliable liver function tests to ensure your liver health is always monitored. Whether you’re looking to screen for liver diseases or monitor ongoing treatment, our team of experts is here to guide you through the process. Schedule your liver function test today and take proactive steps towards better liver health!
