Liver function test

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LIVER FUNCTION TEST
LIVER FUNCTION TEST
To assess
- Capacity of liver
- To detect the abnormality
- For drug monitoring
- Recovery
Functions of liver
• Metabolic functions:
– Carbohydrate, lipid, protein, minerals & vitamin
• Excretory functions:
– Bile pigments, bile salts & cholesterol
• Protective function & detoxification:
– Kupffer cells, NH3 and xenobiotics detoxification
• Hematological functions:
– Formation of blood in embryo & plasma proteins in adult
• Storage functions:
– Glycogen, vitamins, trace elements
Tests to access liver function
• LFTs are the biochemical investigations to
know the functions and damage of liver
• Liver is a large size factory of safety so it
can perform many of its functions almost
normally despite of damage
• Slelection of the right test is important in
LFT
VARIOUS LIVER FUNCTION TESTS
A) Tests based on abnormal pigment
metabolism
– serum bilirubin and van den Bergh reaction
– urine bilirubin
– urine and fecal urobilinogen
B) Tests based on metabolic capacity
(i) carbohydrate metabolism
- galactose tolerance
- fructose tolerance
(ii) lipid metabolism
- serum cholesterol
- cholesterol ester and their ratio
- fecal fat
(iii) amino acid metabolism
- blood NH3
(iv) drug metabolism
- hippuric acid test
C) TESTS BASED ON SYNTHETIC
FUNCTIONS
- Total serum proteins
- Serum albumin
- A:G ratio
- Plasma fibrinogen
- Prothrombin time and index
D) TESTS BASED ON EXCRETORY
FUNCTIONS
- Bile salts and bile pigments
- Bromosulphathelein test (BSP
retention test)
E) TESTS BASED ON DETOXIFICATION
- Hippuric acid synthesis test
F) TESTS BASED ON SERUM ENZYMES
DERIVED FROM LIVER
- Transaminases
- Alkaline phosphatases
- 5`nucleotidase
-  glutamyltranspeptidase
STANDARD L F T
SERUM BILIRUBIN
NORMAL RANGE
total bilirubin
conjugated
unconjugated
0.2—1.0 mg/dl
<0.2 mg/dl
0.2—0.8 mg/dl
DIRECT AND INDIRECT REACTIONS
Indirect positive--hemolytic jaundice
Direct positive --obstructive
Biphasic
--hepatic
LIVER ENZYMES
A) TRANSAMINASES
•
•
•
•
•
•
-Alanine transaminases (ALT)/SGPT
-Aspartate transaminases (AST)/SGOT
Indicate hepatocellular destruction
ALT—cytoplasm—9-40IU/L—more sensitive
AST---cytoplasm and mitochondria---9-45IU/L
Markedly increased in hepatocellular diseases
Mildly increased in obstructive diseases
AST:ALT RATIO
Severe damage - >1
Mild damage - 1 or <1
Alcoholic liver disease - >2.0
B) ALKALINE PHOSPHATASE (ALP)
Cells lining the biliary canaliculi
normal range :- 25-100 IU/L
raised in obstructive liver diseases x3
hepatocellular diseases
c) GAMMA GLUTAMYL TRANSPEPTIDASE
provide sensitive index
normal level:- <50U/L
hepatic damage:- raised parallel with
transaminases
+++in biliary obstruction (along ALP)
Alcoholism
Drugs
d) 5`NUCLEOTIDASE
Normal range :- 2-15U/l
Raised :- hepatobiliary diseases(along ALP)
Advantage :- not altered in bone diseases
e) others
Serum LDH
IDH
Cholinesterase
Total protein and ALBUMIN
Most abundant serum protein is synthesized solely by liver
Half life :- 21 days
Good marker for chronic liver diseases
Low levels :- chronic liver diseases
- malnutrition
- kidney diseases
A:G ratio
Normal---1.2 –1.5 : 1
PROTHROMBIN TIME (PT)
All clotting factors are synthesized by liver
Liver diseases :- decreased level of clotting
factors
Half life :- 5-72 hrs.
PT:-acute/chronic liver diseases
Role of vitamin K:- Required for the synthesis
of II,VII,IX and X factors
URINARY UROBILINOGEN
Metabolites formed in intestines
Being water soluble present in urine normally
Increased mostly in:-hemolytic jaundice
absent in obstructive pathology

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