Liver Function Tests (LFTs) interpretation | COMPLETE GUIDE

Summary

This video script offers an in-depth look at liver function blood tests, explaining the significance of each component, such as ALT, AST, ALP, GGT, bilirubin, albumin, and prothrombin time. It teaches viewers how to interpret these tests to diagnose liver damage, cholestatic damage, and the liver's synthetic function. The script also discusses the causes of jaundice and how to differentiate between pre-hepatic, hepatic, and post-hepatic conditions, providing valuable insights for medical professionals and patients alike.

Takeaways

• 📌 Liver Function Tests (LFTs) are used to assess liver health and diagnose liver conditions.
• 🔍 ALT and AST are markers of liver cell damage; ALT is more liver-specific compared to AST.
• 📈 An ALT/AST ratio can help differentiate types of liver disease, with ALT > AST usually indicating liver disease and AST > ALT suggesting liver cirrhosis or acute alcoholic hepatitis.
• 🚑 High AST levels can also be due to non-liver causes such as myocardial infarction or rhabdomyolysis.
• 🌐 Common causes of liver damage include alcoholic fatty liver disease, non-alcoholic fatty liver disease, viral hepatitis, drug toxicity, autoimmune hepatitis, and liver cirrhosis.
• 🧪 ALP and GGT are indicators of cholestatic damage, with ALP found in bile ducts and bone, and GGT specific to bile duct cells.
• 🔎 Comparing ALT to ALP levels can help determine the type of liver injury: hepatocellular or cholestatic.
• 🟡 Bilirubin is a hemoglobin breakdown product, and its levels can be raised in certain diseases, affecting the appearance of the skin and eyes (jaundice).
• 🔑 Jaundice can be pre-hepatic, hepatic, or post-hepatic, and patient symptoms can help distinguish the cause.
• 🩸 Albumin, the most abundant blood protein, is involved in fluid balance and transport; low levels can indicate liver damage or other conditions.
• ⏱ Prothrombin time (PT) measures blood clotting and can be affected by liver damage, vitamin K deficiency, or anticoagulant medication.

Q & A

What are the main components of a liver function blood test?

The main components of a liver function test include ALT, AST, ALP, GGT, bilirubin, albumin, and prothrombin time. These components reflect both liver damage and its ability to conjugate and synthesize proteins.

What does it mean when ALT and AST levels are elevated in a liver function test?

Elevated ALT and AST levels indicate damage to the liver cells or hepatocytes, often due to a disease process affecting the liver.

How can the ratio of ALT to AST help in diagnosing liver conditions?

An ALT greater than AST is generally associated with liver diseases, while an AST greater than ALT, especially if AST is more than twice ALT, can indicate liver cirrhosis or acute alcoholic hepatitis.

What is the significance of ALP and GGT in liver function tests?

ALP and GGT are markers for cholestatic damage, indicating a problem with the flow of bile. ALP is also found in bone, so its elevation can also be due to bone damage, while GGT is more specific to bile duct cells.

How can you distinguish between hepatocellular injury and cholestasis using liver function tests?

By comparing the ratio of ALT to ALP. If ALT is 10 times greater than normal with ALP less than three times greater, it suggests hepatocellular injury. If ALT is less than 10 times normal and ALP is over three times greater, it indicates cholestasis.

What are some common causes of liver damage reflected in liver function tests?

Common causes of liver damage include alcoholic fatty liver disease, non-alcoholic fatty liver disease, viral hepatitis, drug toxicity, autoimmune hepatitis, and liver cirrhosis.

What role does bilirubin play in liver function, and how can its levels indicate liver problems?

Bilirubin is a breakdown product of hemoglobin that the liver processes. Elevated bilirubin levels can indicate liver problems, and when it reaches a certain level, it can cause jaundice, which is visible as a yellowing of the skin and eyes.

How can changes in the color of urine and stool help differentiate the causes of jaundice?

Conjugated jaundice causes darker urine due to water-soluble bilirubin in the urine, while post-hepatic jaundice causes pale stools due to the blockage of bile flow, which normally contains bilirubin.

What is the primary function of albumin in the body, and how can its levels be affected by liver damage?

Albumin is the most abundant blood protein, responsible for maintaining oncotic pressure and transporting other molecules. Low albumin levels can result from liver damage, as the liver cannot synthesize it as quickly, or from excessive loss through the kidneys or during an inflammatory response.

What does prothrombin time measure, and how can it be related to liver function?

Prothrombin time measures the time it takes for blood to clot, focusing on the clotting factors in the extrinsic pathway of blood coagulation. It can be high in liver damage, vitamin K deficiency, or due to the effects of medications like warfarin.

How can the information from liver function tests be used to identify different types of liver issues?

Liver function tests can identify hepatocellular damage, cholestatic damage, and reduced synthetic function of the liver by analyzing the levels and ratios of various components like ALT, AST, ALP, GGT, bilirubin, albumin, and prothrombin time.