Liver function tests
THE liver is found in the upper part
of the right side of the abdomen
and extends across the midline to
the left. It performs numerous functions
among which are:
• storage of carbohydrates produced from
• processing of fats (lipids) and proteins
from the diet;
• production of different proteins that are
essential for body functions, for example,
• removal of substances that are poisonous
and toxic to the body; and the production of
The bile produced contains acids, pigments
and waste materials. It traverses ducts in the
liver to enter into the larger common bile
duct which has an appendage called the gall
bladder, which stores some of the bile.
After a meal, bile from the gall bladder is
secreted into the initial part of the small
intestine, called the duodenum, where it
plays an important role in the digestion of
The liver is an organ that has tremendous
powers of regeneration. When a large portion
of the liver is damaged or removed, the organ
will grow back itself.
There are many conditions that affect the
liver including infections, alcohol intake,
medicines, poisons, clotting conditions and
Liver function tests
help in the diagnosis of any liver conditions,
whether there are symptoms and signs like
jaundice, itchiness, enlarged liver as well as
the monitoring of the progress and severity of
existing liver conditions.
Liver function tests are also done when
medical examinations are carried out
routinely or for employment purposes.
The varied functions of the liver result in
the production of various substances which
are found in the bloodstream. The blood
levels of these substances are affected by
various liver conditions. Many of these
substances can be measured by taking a blood
sample and sending it to the laboratory.
The common liver function tests include:
a) Total protein which includes albumin and
all other blood proteins including globulin.
Albumin is the main protein produced by the
liver. Certain liver conditions affect the
production of albumin and other proteins and
this is reflected in reduced levels.
b) Bilirubin is a substance produced from
haemoglobin, which is released when the red
blood cells break down. The liver cells attach
sugar molecules to the bilirubin (conjugated
bilirubin) which is then passed down the bile
ducts and the common bile duct into the
small intestine. The bilirubin which has yet to
have sugar molecules attached to it is called
unconjugated bilirubin. Bile gets its
yellow/green colour from bilirubin.
The unconjugated bilirubin is increased
when there is excessive breakdown of red
blood cells in a condition called hemolytic
anaemia, which has many causes.
The conjugated bilirubin is increased in
conditions affecting the liver and bile duct,
such as chronic alcoholism, hepatitis, liver
injury. It is markedly increased in conditions
in which the flow of bile is blocked, such as a
gallstone stuck in the common bile duct.
c) Alanine transaminase (ALT) is a
compound that hastens the processing of
proteins. There are large amounts of ALT in
the liver cells. When the liver is damaged by
injury or inflammation like hepatitis, the ALT
levels are increased.
d) Aspartate transaminase (AST) is involved
in the synthesis of amino acids or proteins.
AST levels are increased when there is liver
damage, even before there are symptoms. In
general, the AST levels are lower than the ALT
levels. When the AST levels are higher,
especially when it is double or triple the ALT
levels, it generally indicates alcoholic liver.
e) Alkaline phosphatase is an enzyme found
in liver cells adjacent to the bile ducts. The
level is increased in certain liver and bone
f) Gamma glutamyl transferase (GGT) is
another enzyme that is found in liver cells. It
is involved in the break down and clearance
of alcohol by the liver. Its level is increased
when there is heavy alcohol consumption.
When the above
tests show abnormalities, additional tests
may be necessary, depending on the clinical
circumstances. It is usual for a general
practitioner to refer a patient to a specialist
for further tests, which are blood or other
tests. They include:
These tests detect viruses and antibodies to
the viruses that affect the liver, such as
hepatitis A, hepatitis B.
The body can also produce antibodies that
attack certain parts of the body ( autoimmune
conditions ). The autoimmune conditions
affecting the liver include autoimmune
hepatitis and primary biliary cirrhosis. The
former is associated with smooth muscle
antibodies and the latter, anti-mitochondrial
b) Blood clotting studies
The liver produces many of the body's
clotting factors. In certain liver conditions,
this production is decreased and the blood
does not clot well when there is an injury.
Clotting studies may be useful in assessing
the severity of certain liver conditions.
c) Ultrasound scan
An ultrasound examination of the liver can
provide information about certain liver
conditions. It is carried out by applying a
probe to the skin overlying the liver with gel
between the probe and the skin to obtain
d) Liver biopsy
This is a procedure in which a small bit of
tissue is removed from the liver and then sent
to the laboratory where a microscopic
examination is carried out. It involves the skin
over the liver being cleansed with an
antiseptic; injection of local anaesthetic;
holding the breath for a few seconds and the
insertion of a special needle through the skin,
fat and muscle into the liver thereby
removing a sample of liver tissue. The
procedure may be done with an ultrasound
machine to help guide the biopsy needle to
the right site in the liver.
The above tests will help elucidate the
cause of a liver condition as well as monitor
the progress and severity of the condition.
Other tests like computer axial tomography
(CAT) scan or magnetic resonance imaging
(MRI) may also be necessary. Your doctor will
advise you on the need and interpretation of
the results and what to do, if necessary.