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.

Outlines

00:00

🧪 Liver Function Blood Tests Overview

This paragraph introduces the video's focus on liver function blood tests, explaining that viewers will learn about the significance of each test component and how to interpret them for diagnosis. It mentions the main components of the liver function test, including ALT, AST, ALP, GGT, bilirubin, albumin, and prothrombin time, which reflect liver damage, bile flow issues, and the liver's synthetic capabilities. The video encourages viewers to like and subscribe for more informative content.

05:02

📈 Understanding Liver Function Test Results

The second paragraph delves into the specifics of liver function tests, discussing how elevated levels of ALT and AST indicate hepatocellular damage, while ALP and GGT suggest cholestatic damage due to bile flow issues. It explains the ALT/AST ratio's significance in diagnosing liver diseases and cirrhosis. The paragraph also covers the role of ALP and GGT in identifying the source of damage, whether it's from the liver or bones. It further explains the process of bilirubin production and conjugation, how jaundice occurs, and the distinction between pre-hepatic, hepatic, and post-hepatic causes. Additionally, it touches on albumin's role in blood protein synthesis and oncotic pressure, and the importance of prothrombin time in assessing blood clotting related to liver function. The summary concludes by reiterating the video's educational purpose and encouraging viewers to explore more videos on blood test interpretation.

Keywords

💡Liver Function Blood Tests

Liver Function Blood Tests are medical tests that measure various substances in the blood to evaluate liver health and function. In the video, these tests are the central theme, as they help in diagnosing liver damage, cholestatic damage, and the liver's synthetic function. The script explains how different components of these tests reflect specific aspects of liver health.

💡ALT (Alanine Transaminase)

ALT, or Alanine Transaminase, is an enzyme found mainly in the liver. Elevated levels of ALT in the blood can indicate liver cell damage. The script mentions that ALT is a more specific test for liver damage compared to AST, as it is predominantly found in liver parenchymal cells.

💡AST (Aspartate Transaminase)

AST, or Aspartate Transaminase, is another enzyme that, while also present in liver cells, is found in other tissues like the heart and muscles. The video script explains that an AST to ALT ratio can help differentiate between various liver conditions, with an AST greater than ALT possibly indicating liver cirrhosis or acute alcoholic hepatitis.

💡ALP (Alkaline Phosphatase)

ALP is an enzyme located in the bile ducts and bones. The script explains that an increase in ALP levels can indicate damage to the bile ducts or bones, and when combined with an increase in GGT, it suggests cholestatic damage.

💡GGT (Gamma-Glutamyl Transpeptidase)

GGT is an enzyme specific to bile duct cells. The video script states that elevated GGT levels are indicative of cholestatic damage, making it a more specific test for this type of liver issue compared to ALP.

💡Cholestatic Damage

Cholestatic damage refers to a problem with the flow of bile, which carries bilirubin from the liver to the small intestines. The video script explains that markers such as ALP and GGT are raised when there is cholestatic damage, indicating issues with bile flow.

💡Bilirubin

Bilirubin is a breakdown product of hemoglobin and is processed by the liver. The script discusses how elevated bilirubin levels can indicate liver diseases and how the type of jaundice (pre-hepatic, hepatic, or post-hepatic) can be determined based on bilirubin levels and its conjugation state.

💡Albumin

Albumin is the most abundant blood protein, responsible for maintaining oncotic pressure and transporting other molecules. The video script mentions that low albumin levels can result from liver damage, nephrotic syndrome, or inflammatory responses, reflecting the liver's synthetic function.

💡Prothrombin Time (PT)

Prothrombin Time is a measure of how long it takes for blood to clot, specifically looking at the clotting factors in the extrinsic pathway of blood coagulation. The script notes that an elevated PT can be due to liver damage, vitamin K deficiency, or the effect of medications like warfarin.

💡Jaundice

Jaundice is a condition where the skin and eyes appear yellow due to high levels of bilirubin in the blood. The video script explains that jaundice can be caused by pre-hepatic, hepatic, or post-hepatic issues, and the patient's symptoms, such as changes in urine and stool color, can help identify the cause.

💡Hepatocellular Injury

Hepatocellular Injury refers to damage to the liver cells or hepatocytes. The script uses the ratio of ALT to AST to help determine if the liver function test results indicate hepatocellular injury, with an ALT greater than AST typically associated with most liver diseases.

Highlights

Introduction to liver function blood tests and their role in diagnosis.

Explanation of the main components of liver function tests: ALT, AST, ALP, GGT, bilirubin, albumin, and prothrombin time.

ALT and AST as markers of liver cell or hepatocyte damage due to disease processes.

ALP and GGT as indicators of cholestatic damage related to bile flow issues.

ALT's specificity in liver damage assessment due to its predominance in liver parenchymal cells.

AST's presence in multiple organs and its implications for liver damage diagnosis.

The ALT/AST ratio and its association with liver diseases, including cirrhosis and alcoholic hepatitis.

Non-liver causes of high AST levels, such as myocardial infarction or rhabdomyolysis.

Common causes of liver damage, including alcoholic and non-alcoholic fatty liver diseases, viral hepatitis, and drug toxicity.

ALP's role in indicating damage to bile ducts and bones.

GGT as a specific test for cholestatic damage due to its presence in bile duct cells.

Interpreting combined ALP and GGT levels to identify cholestatic issues.

Differentiating hepatocellular injury from cholestasis by comparing ALT and ALP ratios.

Bilirubin's role in the breakdown of hemoglobin and its processing by the liver.

Causes of jaundice and how bilirubin levels can indicate pre-hepatic, hepatic, or post-hepatic issues.

Albumin's function in maintaining blood oncotic pressure and its synthesis in the liver.

Prothrombin time as a measure of blood clotting and its relation to liver function.

Summary of liver function tests' components and their use in identifying liver damage and synthetic function.

Transcripts

hi everyone in this video we will cover

the liver function blood tests

by the end of it you will understand

what each component of the test means

and how to interpret them to help make a

diagnosis

if you find the video useful please

consider liking the video and

subscribing to my channel

these are the main components of the

liver function test

high alt ast

alp and ggt all reflect some form of

damage to the liver

whilst bidirubin albumin and profrombin

time reflects the liver's ability to

conjugate and synthesize protein

firstly let's look at the markers of

liver damage

alt and ast are often raised when the

liver cells or hepatocytes are being

damaged by a disease process

whereas alp and ggt will be raised when

there is a problem with the flow of bile

which carries bilirubin from the liver

to the small intestines

this is known as cholestatic damage

alt is found predominantly in the liver

parenchymal cells and so is released

into the blood when these cells are

damaged ast is also found in liver

parenchymal cells but additionally it's

present in heart muscle skeletal muscle

kidneys and the brain this makes alt a

more specific test for determining liver

damage

when interpreting alt and ast we can

look at a ratio between them

an alt greater than ast is associated

with most liver disease

but ast greater than aot

can be associated with liver cirrhosis

or acute alcoholic hepatitis

particularly if ast is more than two

times greater than alt

a high ast could also be due to

non-liver causes for example myocardial

infarction or rhabdomyolysis

some common causes of liver damage are

alcoholic fatty liver disease

non-alcoholic fatty liver disease

viral hepatitis

drug

toxicity autoimmune hepatitis

and liver cirrhosis which is the end

process of prolonged damage to the liver

alp and ggt are tests for kodostatic

damage

alp is found in the bile duct and bone

so damage to either of these will cause

alp to be released into the blood

ggt is just found in bile duct cells

making it a more specific test for

cholestatic damage

so if you see a rise in both alp and ggt

you can be fairly confident it's due to

codeostasis

a rise in alp alone is caused by damage

to bone

to help distinguish whether lfts are

showing you her pathocellular injury

versus codiostasis we can compare the

ryzen alt with the ryzen alp

if the alt is 10 times greater than it

should be with alp being less than three

times greater it's probably

hepatocellular injury

if aot is less than 10 times normal

value with the alp over three times

greater than its normal value there's

cody

stasis it's also possible to have a

mixed picture of liver damage and

codeostasis

to finish we're going to look at the

markers of synthetic function

bilirubin is a breakdown product of

hemoglobin so it's released into the

blood when red blood cells hemolyze

this is usually a natural part of the

red blood cell cycle where bilirubin

will travel to the liver

a healthy liver will conjugate bilirubin

which means a molecule is added to it

conjugated bidirubin is water-soluble so

it can be excreted by the kidneys into

the urine

some bilirubin is also excreted via the

bile duct into the feces

bilirubin is raised in some diseases

when it reaches a level of 60 micromoles

per liter in blood the patient will

appear jaundice

causes of jaundice can be divided into

pre-hepatic

hepatic and post-hepatic

pre-hepatic jaundice is due to excess

production of bilirubin i.e pathological

hemolysis

since this process occurs before the

bilirubin has reached the liver it will

be unconjugated

hepatic causes of jaundice are those

that prevent the liver from processing

bilirubin efficiently

post-hepatic jaundice is caused by

anything that blocks the flow of bile

from the liver to the small intestines

we can help distinguish between these

three causes by asking the patient about

changes in color to urine and stool

a conjugated jaundice will cause the

urine to become darker since conjugated

bilirubin is water-soluble and will end

up in the urine

post-hepatic jaundice will also cause

stools to become pale since it blocks

the flow of bilirubin containing bile

into the small intestines where

bilirubin would usually give stool a

darker colour

albumin is the most abundant blood

protein in the body

its main functions are to maintain

oncotic pressure in the blood which

stops fluid leaking out of blood vessels

and is also a transporter protein for

other molecules in the blood

albumin can be low in liver damage as it

can't be synthesized as fast

it could also be caused by excessive

loss of albumin through the kidneys in

nephrotic syndrome

it's also low during an inflammatory

response

finally prothrombin time is a

measurement of how long our blood takes

to clot

more specifically it looks at the

clotting factors in the extrinsic

pathway of blood coagulation i'll cover

this topic in another video

pt can be high if a patient takes

warfarin which means the drug is working

also in vitamin k deficiency

and liver damage

so to summarize we've covered all the

major components of lfts and how they

can be used to identify liver damage

cholestatic damage and reduce synthetic

function of the liver

thanks for watching and feel free to

check out my other videos on

interpreting blood tests see you next

time