Liver function tests

Introduction:

The liver is crucial in metabolism, digestion, detoxification, and removing waste from the body. Additionally, it plays a vital part in regulating red blood cells, synthesizing glucose, and storing it. Liver Function Tests (LFTs) are blood examinations that gauge different substances produced by the liver, such as proteins, enzymes, and bilirubin. Fluctuations in the levels of these substances, whether higher or lower, aid in assessing overall health, liver function, and the presence of any liver ailments or injuries. 

The liver function tests typically include alanine transaminase (ALT) and aspartate transaminase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), serum bilirubin, prothrombin time (PT), bilirubin, lactate dehydrogenase, total protein, and albumin. It also helps identify any other sources of disease. These tests play a vital role in pinpointing the source of the damage. 

Indications: 

LFTs are done to determine if the liver is damaged or diseased and is causing specific symptoms, to identify the severity of liver disease and the progress of the disease, to plan the treatment, to monitor the liver disease after initiating therapy, and to determine the prognosis. It is also used to identify the side effects caused by certain medications that can affect the liver. 

LFTs are prescribed if an individual has clinical symptoms of nausea, vomiting, decreased appetite, Fatigue, Weakness, swelling associated with or without pain in the abdomen, increased itching, and Swelling in your ankles and legs. It is also done to check for jaundice, which turns the skin and eyes yellow. It is also prescribed when the color of the urine changes to dark or when passing light-colored stool. 

Certain conditions that need LFTs include family history, alcohol abuse, obesity, diabetes, medicines that can damage the liver, and viral infections like hepatitis. 

Parts of LFTs:

Various tests are done as part of liver function tests. These components are altered in multiple liver diseases. They are as follows: 

• Aminotransferases: Aminotransferases contain enzymes called aspartate transaminase (AST) and alanine transaminase (ALT). These give the status of liver injury. They are released into the blood for liver injuries. They are higher in men and obese individuals. ALT is more specific for liver diseases than AST. Elevated levels of ALT are mainly seen in viral hepatitis and non-alcoholic steatohepatitis. Persistently elevated levels are seen in viral liver infections. ALT is also called the SGPT test.
• AST can be elevated in liver diseases, muscle damage like cardiac diseases, and liver cirrhosis. AST is also called the SGOT test. An increase in equal levels of both ALT and AST indicates non-alcoholic injuries which are due to infections. An increase in AST levels twice as much as ALT indicates alcohol-related liver injury. 
• AST/ALT ratio: This is a part of LFT used to diagnose liver diseases. Various ratios indicate various diseases. The elevated levels mainly indicate alcoholic hepatitis and cirrhosis. 
• Albumin and total protein: Albumin is a vital protein synthesized in the liver. Toral protein levels measure the albumin and globulin levels in the blood. Albumin performs various functions in the body and fights infections. Decreased albumin and total protein levels indicate liver damage or disease, gastrointestinal disorders, and kidney diseases.  High levels of albumin indicate dehydration. 
• Alkaline phosphatase (ALP): An enzyme in both the liver and bone necessary for protein metabolism. Increased ALP levels are seen in liver diseases like blocked bile ducts. It is also elevated in certain bone diseases. 
• Bilirubin levels: Bilirubin is a by-product of red blood cells in the body. They are eliminated in stools. Elevated bilirubin levels indicate liver damage, blocked ducts of the liver, and anemia. Higher levels of bilirubin in the blood are called jaundice, a condition that causes the skin to turn yellow. 
• Gamma-glutamyl transferase (GGT) is more specific for liver and biliary diseases. It is found mainly in liver and bile duct cells. Its levels rise significantly in liver diseases, alcoholism, and non-alcoholic fatty liver diseases. 
• Lactate Dehydrogenase (LDH) is an enzyme in the liver and many other body parts. Elevated levels indicate liver damage. As many tissues synthesize LDH and are responsible for many chemical reactions in the body, elevated levels can be seen in many bones, muscles, liver diseases, and even cancers. 
• Prothrombin Time (PT): Prothrombin is a clotting factor secreted by the liver. PT is the time taken by the blood to clot. Increased PT levels are seen in liver damage and when taking medications like warfarin. 

Before LFTs: 

LFTs are done on an empty stomach. Hence, it is advisable not to eat or drink at least 10–12 hours before the test. It is better to inform the healthcare professional of all the medications that are being taken. 

During the test: 

Following the sterilization of the area, a small needle is utilized to extract blood from a vein. The appropriate amount of blood is subsequently gathered into a vial and forwarded to the laboratory for examination. 

After the test: 

One can continue daily activities after the test. The results will depend on the laboratory standards. Abnormal values indicate liver damage or disease and will be interpreted by a pathologist. Based on the results, further investigations will be done to confirm the diagnosis, and medications will be prescribed. 

Risks and Complications: 

LFT is not associated with risks or complications. The main risk associated with these is soreness of the arm and bruising at the needle insertion site, which subsides after some time. 

Conclusion: 

Liver function tests (LFTs) are vital blood tests that help evaluate the liver's health and diagnose many other abnormalities. By measuring substances produced by the liver, such as enzymes and proteins, LFTs provide an understanding of liver function and detect any potential liver diseases or injuries. LFTs play a significant role in assessing liver health and ensuring the early detection and management of liver diseases.