Liver function tests and interpretation is a very important topic for students of medical and allied fields. It is essential for efficient practice of clinical and laboratory medicine.

1. Dr.S.Sethupathy, M.D,Ph.D,
Professor of Biochemistry,
RMMC, AU

2. Battery of tests
 Liver function tests are useful for
• the diagnosis
• assessment of prognosis
• monitoring of liver diseases.
 Liver carries out diverse functions
 So a battery of tests are needed.

3. Liver functions
1. Excretory function
 Liver is involved in the uptake, conjugation
and excretion of bilirubin derived from
degradation of heme in reticuloendothelial
system.
 The conjugated bilirubin is excreted via bile.
 Liver also detoxifies ammonia, drug
metabolites and xenobiotics.

4. 2.Metabolic functions
 carbohydrate metabolism- glycogen metabolism,
gluconeogenesis, blood glucose maintenance.
 Lipid metabolism
 Cholesterol metabolism, bile acid synthesis,
metabolism of lipoproteins, VLDL and triacyglycerol .
synthesis
 Protein metabolism
 Catabolism of proteins, synthesis of non- essential
amino acids, formation of urea from ammonia

5. 3 . Synthesis of plasma
proteins
Liver synthesizes albumin,
coagulation factors such as
prothrombin.
4. Storage function
Vitamin A, D, K, B12
 Iron stored as Ferritin

6. Serum Enzymes
 Serum enzymes
 In liver cell damage, liver tissue enzymes
leak into circulation and their levels are
increased in plasma.
 Aspartate transaminase (AST) - SGOT
 Alanine transaminase (ALT)- SGPT
 Alkaline phosphatase(ALP)
 Gamma glutamyl transpeptidase (GGT)

7. Bilirubin metabolism
 Heme is degraded in reticuloendothelial system
 Iron is reutilized.
 Globin protein – catabolized into amino acids
 The bilirubin is formed from porphyrin ring of
heme which is water insoluble
 It is called unconjugated bilirubin.
 Unconjugated bilirubin is transported by albumin
to liver.

8. Role of liver
Liver takes up unconjugated bilirubin
Conjugates them to bilirubin
diglucuronide using UDP-glucuronyl
transferase
Glucuronyl units provided by UDP-
glucuronic acid.
Conjugated bilirubin is water soluble
and excreted in bile.

9.  In the intestine- Conjugated bilirubin
gets deconjugated by bacterial beta-
glucuronidase enzyme in the terminal
ileum and large intestine.
 The pigment is further reduced by fecal
flora to a group of colorless, tetra pyrrolic
compounds known as urobilinogens.
 A small fraction of urobilinogens is
absorbed in the terminal ileum and re-
excreted by liver.
 This is called enterohepatic circulation.

10. Then some of the urobilinogens being
water soluble, escape into urine normally.
In the intestine, further reduction of
urobilinogens form stercobilinogen which
is excreted in feces.
Urobilin and stercobilin , yellow in color
are formed from urobilinogen and
stercobilinogen respectively.

11. Jaundice is the yellowish discoloration of
skin , mucous membrane and sclera.
It is due to hyperbilirubinemia.
Normal serum bilirubin level is 0.2 - 1 mg/dl.
 Hyperbilirubinemia may be of conjugated or
unconjugated or both.
 Normal serum unconjugated bilirubin level
is 0.2-0.8 mg/dl and conjugated bilirubin
level is 0.2-0.4 mg/dl.
 Jaundice clinically appears when the serum
bilirubin level goes beyond 3 mg/dl.

13. Conjugation

16. Vanden bergh test
 Bilirubin reacts with diazotized sulfanilic acid to form
purple colored complex azobilirubin.
 Conjugated bilirubin gives color in aqueous medium
immediately and it is direct positive.
 Unconjugated bilirubin, in methanol only color develops
and it is indirect positive.
 If both fractions are there, the color developed in aqueous
medium deepens on adding methanol and is called
biphasic.
 Van den Bergh test is indirect positive in hemolytic
jaundice, direct positive in obstructive jaundice and
biphasic in hepatic jaundice.

18. Hemolytic Jaundice
 Hemolytic jaundice or pre-hepatic jaundice or
unconjugated hyperbilirubinemia
 Investigations
 Serum unconjugated bilirubin is increased.
 Urine bile salts and bile pigments will be negative.
 So it is called as acholuric jaundice.
 Urine urobilinogen will be excess.
 Motion is high colored (dark brown).
 Causes
 Hemolytic anemia, hemoglobinopathies, mismatched
blood transfusion.

19. Inborn errors
 Gilbet’s syndrome (GS): is the most common
hereditary cause of increased bilirubin
 characterized by elevated levels of unconjugated
bilirubin in the bloodstream.
 Enzyme glucuronyltransferase deficiency.
 Crigler Najjar syndrome: It is a rare , AR disorder
with high levels of unconjugated
hyperbilirubinemia affecting brain.
 UDP- glucuronyl transferase enzyme is defective.

20.  Obstructive jaundice or post hepatic jaundice
or conjugated hyperbilirubinemia
 Serum conjugated bilirubin is increased.
 Urine bile salts, bile pigments will be positive.
 Urine urobilinogen will be less or absent.
 Motion is clay colored.
 Causes
 Biliary duct obstruction - due to gall stones,
tumor in the bile duct, carcinoma head of
pancreas, lymph node enlargement in porta
hepatis,

21. Inborn errors
 Dubin Johnson syndrome : AR disorder
 Increase of conjugated bilirubin in the serum without
elevation of liver enzymes (ALT, AST).
 Defective secretion of conjugated bilirubin into the
bile. Liver cell are pigmented.
 Rotor syndrome . Rare , AR disorder with increase in
conjugated bilirubin
 similar to Dubin Johnson syndrome except that the
liver cells are not pigmented.

22. Hepatic jaundice
 Both unconjugated and conjugated bilirubin levels
are increased in serum.
 Urine bile salts, bile pigments are positive.
 Urine urobilinogen is lesser than normal amounts.
 Motion is pale yellow colored.
 Causes
 Alcoholic hepatitis, viral hepatitis, drug induced
intra hepatic cholestasis.

23.  Tests based on synthesis of plasma
proteins
 Serum albumin level - half- life is 20 days.
 In liver cirrhosis, albumin level is decreased.
Normal serum albumin level is 3.5-4.5 gm/dl
and globulin level is 2.5-3.5 gm/dl.
 Normal albumin globulin ratio (AG ratio) is
1.2 to 1.8 :1 . In cirrhosis, AG ratio is reversed
 Serum globulins are increased in chronic
active hepatitis and cirrhosis of liver.

24. Prothrombin time
 Normal – 10-14 secs.
 In liver dysfunction, it is prolonged.
 It is not recovered by Vitamin K
administration.
 In vitamin K deficiency due to obstructive
jaundice also, there will be prolonged
prothrombin time
 But that will recover after parenteral
administration of vitamin K.

25.  Tumor marker- α-feto protein (AFP) is elevated in
hepatocellular carcinoma.
 Ceruloplasmin
 Its level is decreased in Wilson’s disease.
 Serum protein electrophoresis
 In cirrhosis of liver, albumin is decreased and gamma
globulins are increased.
 In biliary obstruction, α2 and β2 globulins are
increased.

26. Serum enzymes
 Hepatocellular damage
 Serum amino transferases- Aspartate amino transferase (AST)
and Alanine amino transferase (ALT) are elevated.
 Normally both are lesser than 40 U/L.
 In acute hepatitis, may increase to more than 1000 U/L.
 ALT is found in cytosol and is more liver specific.
 AST/ALT ratio is lesser than 1.
 But in alcoholic hepatitis, AST is increased more than ALT and
the ratio is more than 2. This is due to release of AST from
mitochondria.
 ALT > AST is seen in chronic liver disease
 AST > ALT is seen in cirrhosis and acute alcoholic hepatitis

27. Approach to diagnosis
 ALT is a useful marker of hepatocellular injury.
 ALP is a useful indirect marker of cholestasis.
 First assess ALT and ALP
 Compare ALT and ALP raise?
 A greater than 10-fold increase in ALT and a less than 3-fold
increase in ALP suggests hepatocellular injury
 A less than 10-fold increase in ALT and a more than 3-fold
increase in ALP suggests cholestasis
 It is possible to have a mixed picture
involving hepatocellular injury and cholestasis
 5-nucleotidase enzyme is increased in hepatobiliary
disease.

28. Gamma-glutamyl transferase
 A markedly raised ALP with a raised GGT is highly
suggestive of cholestasis.
 It can also be raised in response to alcohol and drugs
such as phenytoin.
 ALP rise in the absence of a raised GGT – can be due to
non-hepatobiliary pathology.
 Alcohol and certain drugs (eg, some
anticonvulsants, warfarin) can induce hepatic
microsomal (cytochrome P-450) enzymes
 Markedly increase GGT

29. Isolated ALP elevation
Focal liver lesions (eg, abscess,
tumour)
Partial or intermittent bile duct
obstruction (eg, stone,
stricture, cholangiocarcinoma
Syphilitic hepatitis
Occasionally infiltrative disorders

30. Isolated ALP elevation
In the absence of any apparent liver or biliary
disorder:
 Cancers without liver involvement (eg,
bronchogenic carcinoma, Hodgkin lymphoma,
renal cell carcinoma)
 After ingestion of fatty meals ( from small
intestine)
 Pregnancy (from placenta)
 Children and adolescents ( bone growth)
 Chronic renal failure

31. Isolated bilirubin rise
 An isolated rise in bilirubin is suggestive of a pre-
hepatic cause of jaundice.
 Causes of isolated jaundice include:
 Gilbert’s syndrome (most common cause)
 Haemolysis (check blood film, full blood count,
reticulocyte count, haptoglobin and LDH levels to
confirm)

32. Serum Immunoglobulins
 In chronic liver disorders, Sr.immunoglobulins often
increase.
 Levels increase slightly in acute hepatitis, moderately
in chronic active hepatitis, and markedly in
autoimmune hepatitis.
 Usually very high in different disorders:
 IgM in primary biliary cholangitis (also called primary
biliary cirrhosis)
 IgA in alcoholic liver disease
 IgG in autoimmune hepatitis

33. Antibodies
Autoimmune hepatitis:
 Smooth muscle antibodies against actin
 Antinuclear antibodies (ANA)
 Antibodies to liver-kidney microsome type 1 (anti-LKM1)
 Primary biliary cholangitis
 Antimitochondrial antibody is key to the diagnosis.
 Primary sclerosing cholangitis
 Perinuclear antineutrophil cytoplasmic antibodies
(p-ANCA)

34. Antibodies
 Antimitochondrial antibodies-
 high titers, in > 95% of patients with primary biliary
cholangitis.
 Autoimmune hepatitis
 Drug-induced hepatitis
 myasthenia gravis, autoimmune thyroiditis, Addison
disease, and autoimmune hemolytic anemia
 Antimitochondrial antibodies - usually absent in
extrahepatic biliary obstruction and primary
sclerosing cholangitis.

35.  Blood ammonia
 It is increased in severe hepatocellular
damage either acute or chronic. Normal
blood ammonia level - 15- 60 µg/dl.
 Serum bile acids
 They are increased in liver disease with
cholestasis.

36. CSF glutamine level

37.  Bromosulphathalein (BSP) excretion test
 BSP dye (5mg/kg, 5% w/v solution ) given by
intravenous route is rapidly removed by liver and
excreted in bile.
 Normally 95% of dye is cleared within 45 minutes
 only less than 5% of dye is found in blood after 45
min.
 In hepatic dysfunction, it is more than 5%.
 Higher level of dye after 2 hours than at 45 min ,
the secondary rise is diagnostic of Dubin Johnson
syndrome.

38. Unconjugated Conjugated
Hemolytic anemia Obstruction of biliary
tree
Physiological jaundice Dubin-Johnson
syndrome
Crigler-Najjar
syndrome type I & II
Rotor syndrome
Gilbert syndrome Hepatitis (Both)
-conj and unconj
Toxic
hyperbilirubinemia

39. LFT- Reference range

40. Urobilinogen
Faecal (50-250 mg/day)
Increased in hemo.J
Absent in Obst.J
Complete absent in maligancy
Urine (<4 mg/day)
Obstr.J - no urobilinogen
Hemolytic J – increased urobilinogen with no
bilirubin

41. Liver screen
 LFTs
 Immunoglobulins – IgM/IgG
 Alpha-1 Antitrypsin – Alpha-1 Antitrypsin deficiency
 Serum Copper – Wilson’s disease
 Ceruloplasmin – Wilson’s disease
 Ferritin – Haemochromatosis
 Coagulation screen

42. Liver screen
 Hepatitis serology (A/B/C)
 Epstein-Barr Virus (EBV)
 Cytomegalovirus (CMV)
 Anti-mitochondrial antibody (AMA)
 Anti-smooth muscle antibody (ASMA)
 Anti-liver/kidney microsomal antibodies (Anti-LKM)
 Anti-nuclear antibody (ANA)
 p-ANCA