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
anything abnormal.
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")

Bilirubin

Albumin

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 range.
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:
Disease
Test or Procedure
NonAlcoholic
Steatohepatitis(NASH)
Liver Biopsy
Hepatitis A
Antibody Test (Blood Sample)
Hepatitis B
Antibody & Antigen Tests Hepatitis B DNA
(Blood Sample).
[Liver Biopsy if chronic]
Hepatitis C
Antibody Test/Hepatitis C RNA (Blood
Sample).
[Liver Biopsy if chronic]
Primary Biliary Cirrhosis
Biopsy/Bile duct imaging
Primary Sclerosing Cholangitis Biopsy/Bile duct imaging
Haemochromatosis
HFE gene analysis for C282Y mutation
(Blood Sample)
Autoimmune Hepatitis
Liver Biopsy
Wilson’s Disease
Genetic Analysis/Copper studies (Blood and
Urine Samples)
Alcohol Related Liver Disease
Liver Biopsy/Liver Function Tests