Liver function tests
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Liver function tests (LFTs or LFs), which include liver enzymes, are groups of clinical
biochemistry laboratory blood assays designed to give information about the state of a
patient's liver. Most liver diseases cause only mild symptoms initially, but it is vital that these
diseases be detected early. Hepatic (liver) involvement in some diseases can be of crucial
importance. This testing is performed by a medical technologist on a patient's serum
or plasma sample obtained by phlebotomy. Some tests are associated with functionality
(e.g., albumin); some with cellular integrity (e.g., transaminase) and some with conditions
linked to the biliary tract (gamma-glutamyl transferase and alkaline phosphatase). Several
biochemical tests are useful in the evaluation and management of patients with hepatic
dysfunction. These tests can be used to (1) detect the presence of liver disease, (2)
distinguish among different types of liver disorders, (3) gauge the extent of known liver
damage, and (4) follow the response to treatment. Some or all of these measurements are
also carried out (usually about two times a year for routine cases) on those individuals
taking certain medications- anticonvulsants are a notable example- in order to ensure that
the medications are not damaging the person's liver.
Contents
[hide]
1 Standard liver panel
2 Other tests commonly requested alongside LFTs
o
2.1 5' nucleotidase (5'NTD)
2.2 Coagulation test (e.g. INR)
2.3 Serum glucose (BG, Glu)
2.4 Lactate dehydrogenase (LDH)
3 See also
4 References
5 External links
[edit]Standard
liver panel
This section is missing citations or needs footnotes. Please help add inline
citations to guard against copyright violations and factual inaccuracies. (Novembe
2008)
Measurement Significance
Reference
range
(Normal
Values)
4.4| Albumin is a protein made specifically by the liver, and can be measured
cheaply and easily. It is the main constituent of total protein; the remaining
fraction is called globulin (including the immunoglobulins). Albumin levels are
decreased in chronic liver disease, such as cirrhosis. It is also decreased in
3.9 to 5.0
nephrotic syndrome, where it is lost through the urine. Poor nutrition or states of
g/dL [1]
protein catabolism may also lead to hypoalbuminaemia. The half-life of albumin
is approximately 20 days. Albumin is not considered to be an especially useful
marker of liver synthetic function; coagulation factors (see below) are much
more sensitive
22.3| Alanine transaminase (ALT), also called Serum Glutamic
Pyruvate Transaminase (SGPT) or Alanine aminotransferase (ALAT) is
an enzyme present in hepatocytes (liver cells). When a cell is damaged, it leaks
9 to 60 IU/L[1]
this enzyme into the blood, where it is measured. ALT rises dramatically in acute
liver damage, such as viral hepatitis or paracetamol (acetaminophen) overdose.
Elevations are often measured in multiples of the upper limit of normal (ULN).
22.0| Aspartate transaminase (AST) also called Serum Glutamic Oxaloacetic
Transaminase (SGOT) or aspartate aminotransferase (ASAT) is similar to ALT in
that it is another enzyme associated with liver parenchymal cells. It is raised in
acute liver damage, but is also present in red blood cells, and cardiac and skeletal 10 to 40
muscle and is therefore not specific to the liver. The ratio of AST to ALT is
IU/L[1]
sometimes useful in differentiating between causes of liver damage.[2][3] Elevated
AST levels are not specific for liver damage, and AST has also been used as
a cardiac marker.
113.2| Alkaline phosphatase (ALP) is an enzyme in the cells lining the biliary
30 to 120
ducts of the liver. ALP levels in plasma will rise with large bile duct obstruction,
intrahepatic cholestasis or infiltrative diseases of the liver. ALP is also present
IU/L[1]
in bone and placental tissue, so it is higher in growing children (as their bones
are being remodelled) and elderly patients with Paget's disease.
0.3| Bilirubin is a breakdown product of heme (a part of haemoglobin in red
blood cells). The liver is responsible for clearing the blood of bilirubin. It does
this by the following mechanism: bilirubin is taken up
into hepatocytes, conjugated (modified to make it water-soluble), and secreted
into the bile, which is excreted into the intestine.
Increased total bilirubin causes jaundice, and can signal a number of problems:
1. Prehepatic: Increased bilirubin production. This can be due to a
number of causes, including hemolytic anemias and internal hemorrhage.
0.21.2
mg/dL
2. Hepatic: Problems with the liver, which are reflected as deficiencies in
bilirubin metabolism (e.g. reduced hepatocyte uptake, impaired conjugation
of bilirubin, and reduced hepatocyte secretion of bilirubin). Some examples
would be cirrhosis and viral hepatitis.
3. Posthepatic: Obstruction of the bile ducts, reflected as deficiencies in
bilirubin excretion. (Obstruction can be located either within the liver or in
the bile duct.
0.1| The diagnosis is narrowed down further by looking at the levels of direct
bilirubin.
If direct (i.e. conjugated) bilirubin is normal, then the problem is an
excess of unconjugated bilirubin, and the location of the problem is upstream
of bilirubin excretion. Hemolysis, viral hepatitis, or cirrhosis can be
00.3 mg/dL
suspected.
If direct bilirubin is elevated, then the liver is conjugating bilirubin
normally, but is not able to excrete it. Bile duct obstruction by gallstones or
cancer should be suspected.
85.2| Although reasonably specific to the liver and a more sensitive marker for
cholestatic damage than ALP, Gamma glutamyl transpeptidase (GGT) may be
elevated with even minor, sub-clinical levels of liver dysfunction. It can also be
0 to 51 IU/L[1]
helpful in identifying the cause of an isolated elevation in ALP. (GGT is raised in
chronic alcohol toxicity).
[edit]Other
tests commonly requested alongside LFTs
Pathophysiology sample values
BMP/ELECTROLYTES:
Na+=140
Cl=100
BUN=20
Glu=150
K+=4
CO2=22
PCr=1.0
ARTERIAL BLOOD GAS:
HCO3-=24
paCO2=40
paO2=95
pH=7.40
ALVEOLAR GAS:
pACO2=36
pAO2=105
A-a g=10
OTHER:
Ca=9.5
Mg2+=2.0
PO4=1
CK=55
BE=0.36
AG=16
SERUM OSMOLARITY/RENAL:
PMO = 300
PCO=295
POG=5
BUN:Cr=20
URINALYSIS:
UNa+=80
UCl=100
UAG=5
FENa=0.95
UK+=25
USG=1.01
UCr=60
UO=800
PROTEIN/GI/LIVER FUNCTION TESTS:
LDH=100
TP=7.6
AST=25
TBIL=0.7
ALP=71
Alb=4.0
ALT=40
BC=0.5
AST/ALT=0.6
AF alb=3.0
SAAG=1.0
BU=0.2
SOG=60
CSF:
CSF alb=30
[edit]5'
CSF glu=60
CSF/S alb=7.5
CSF/S glu=0.4
nucleotidase (5'NTD)
5' nucleotidase is another test specific for cholestasis or damage to the intra or extrahepatic
biliary system, and in some laboratories, is used as a substitute for GGT for ascertaining
whether an elevated ALP is of biliary or extra-biliary origin.
[edit]Coagulation
test (e.g. INR)
The liver is responsible for the production of coagulation factors. The international
normalized ratio (INR) measures the speed of a particular pathway of coagulation,
comparing it to normal. If the INR is increased, it means it is taking longer than usual for
blood to clot. The INR will only be increased if the liver is so damaged that synthesis
of vitamin K-dependent coagulation factors has been impaired: it is not a sensitive measure
of liver function.
It is very important to normalize the INR before operating on people with liver problems
(usually by transfusion with blood plasma containing the deficient factors) as they could
bleed excessively.
[edit]Serum
glucose (BG, Glu)
The liver's ability to produce glucose (gluconeogenesis) is usually the last function to be lost
in the setting of fulminant liver failure.
[edit]Lactate
dehydrogenase (LDH)
Lactate dehydrogenase is an enzyme found in many body tissues, including the liver.
Elevated levels of LDH may indicate liver damage.
[edit]See
also
Reference ranges for blood tests
Elevated transaminases
Liver disorders and liver diseases.
[edit]References
1. ^ a b c d[broken citation]
2. ^ Nyblom H, Berggren U, Balldin J, Olsson R (2004). "High AST/ALT ratio may
indicate advanced alcoholic liver disease rather than heavy drinking". Alcohol
Alcohol. 39 (4): 3369. doi:10.1093/alcalc/agh074. PMID 15208167.
3. ^ Nyblom H, Bjrnsson E, Simrn M, Aldenborg F, Almer S, Olsson R (September
2006). "The AST/ALT ratio as an indicator of cirrhosis in patients with PBC". Liver
Int. 26 (7): 8405. doi:10.1111/j.1478-3231.2006.01304.x. PMID 16911467.
