liver function tests
This page contains information on:
- Liver function tests
- Liver ultrasound
- Liver biopsy
LIVER FUNCTION TESTS
During the time when you are being diagnosed or monitored with a liver disease there are a number of tests and procedures
that will be performed. The most basic is a series of tests on a sample of your blood. These are known as "Liver Function
Tests" or simply abbreviated to "LFTs". This information sheet may help you understand what is involved when these tests and
results are discussed.
Liver function tests are performed in your GP surgery, in
hospital and in many other areas where you may be being investigated for liver disease. The procedure requires a sample of
blood to be taken, quite often for a number of different tests including liver function tests. You may see a number of bottles
or containers lined up for a sample of your blood or just one for the liver function test alone.
It is quite important to remember that no test is completely
accurate and one test is a snapshot of your health at the time it was taken. It is good practice to do a number or series
of tests over time to allow the doctor, nurse or specialist to examine a trend in your results, especially if the tests detect
The liver function test is actually a number of parts, each
looking at different properties of your blood, which indirectly can tell you something about how the liver is working. The
most common parts to the test you may have are:
- Alanine Aminotransferase (ALT)
- Aspartarte Aminotransferase (AST)
- Alkaline Phosphatase (ALP)
- Gamma-Glutamyl Transferase (GGT or "Gamma GT")
- Clotting Studies (Prothrombin Time)
Each of these parts have results assigned to them in numbers
and values. Each laboratory in the UK provides a "normal value" or "reference value" to the test, which can give the doctor,
nurse or specialist a guide as to whether or not your test is in the average for normal function or is outside of the normal
range and may be abnormal. How abnormal can be assumed from how low or more often high the result is below or above the normal
Due to the differences in normal range for different laboratories
it can be difficult to compare or comment on individual test results specifically. This is due to the different brand of tests
that they use from different manufacturers and how these are interpreted. There are international normal ranges that all doctors,
nurses and specialists will be familiar with as an approximate guide.
Interestingly the normal values for liver function tests
will vary between men and women, at different times of the day and will change as you get older.This needs to be recognised
when a series of tests are performed over time and they should preferably be performed in a predictable routine to reduce
the variation over time (for example always in the morning or the afternoon, but consistently).
Different diseases of the liver will cause differing types
of damage and affect liver function tests accordingly. It can be possible to give an idea of which disease may be suspected
from a liver function test, but these tests are not the absolute way of diagnosing liver disease. They are helpful, but only
part of the picture. They are also useful for monitoring someone with liver disease, but are not always accurate.
It is well known in some liver diseases that the liver function
test does not accurately portray the extent of inflammation or fibrosis, which can be misinterpreted as suggesting that the
liver may be in better condition than it is. This does not apply to the majority of people living with liver disease, but
it should be remembered.
Usually the liver function test gives an indication of the
degree if inflammation and possibly either damage or change in the ability of the liver to work properly.
The ALT and AST provide an indication of the degree of inflammation
as well as the possible causes.
Both ALP and Gamma GT increases can be suggestive of obstructive
liver disease (e.g. in "cholestatic liver disease" when bile is not transported from the liver adequately due to obstruction
of the bile duct. Gamma GT is also an indicator of alcohol usage.
Bilirubin increases are suggestive of liver disease, especially
in disease of the bile ducts.
Albumin may decrease in chronic liver disease, particularly
if it is worsening, though it may be decreased for other reasons, such as in protein deficiency (e.g. malnutrition).
Clotting studies may be suggestive of liver disease, especially
worsening chronic liver disease if the Prothrombin Time is prolonged, as the liver is significantly involved in the normal
clotting of blood.
All of the above can be affected by disorders and diseases
that do not affect the liver directly and therefore further investigation is extremely important if any results are found
to be outside of the normal range in a liver function test.
When diagnosing liver disease, often, but not always the
most useful test in each disease could be:
||Test or Procedure |
||Liver Biopsy |
||Antibody Test (Blood Sample) |
Antibody & Antigen Tests Hepatitis B DNA (Blood Sample).
Biopsy if chronic]
||Antibody Test/Hepatitis C RNA (Blood Sample).|
|Primary Biliary Cirrhosis
||Biopsy/Bile duct imaging |
|Primary Sclerosing Cholangitis
||Biopsy/Bile duct imaging |
||HFE gene analysis for C282Y mutation (Blood Sample) |
||Liver Biopsy |
||Genetic Analysis/Copper studies (Blood and Urine Samples) |
|Alcohol Related Liver Disease
||Liver Biopsy/Liver Function Tests |