Liver function tests and interpretation for clinical practice

1. Dr.S.Sethupathy, M.D,Ph.D,
Professor &Head,
Dept.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 synthesis, synthesis
of triacyglycerol .
 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 as
Ferritin are stored in liver.

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)
 Alanine transaminase (ALT)
 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
It is involved in the uptake of
unconjugated bilirubin and conjugates
them to bilirubin diglucuronide by the
enzyme UDP-glucuronyl transferase
using UDP- glucuronic acid, the active
donor of glucuronyl units. The
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.
Some Urobilinogen gets back to liver
and reexcreted into intestine via bile . This
is enterohepatic circulation.
Oxidized products form urobilin and
stercobilin which are yellow colored.

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. Vanden bergh test
 Bilirubin reacts with diazotized sulfanilic acid to form
purple colored complex azobilirubin.
 Conjugated bilirubin gives color in aqueous medium
immediately and is direct positive.
 Unconjugated bilirubin, in methanol only color develops
and 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.

14. 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.

15. 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.

16.  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,

17. 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.

18. 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.

19.  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.

20. 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.

21.  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.

22. 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.

23. Obstructive liver disease
 Serum alkaline phosphatase (ALP) level is increased in
case of cholestasis, hepatic carcinoma and biliary tract
obstruction.
 ALP is present in bone, liver, intestine and placenta.
 In the absence of bone disease or pregnancy, ALP elevation
indicates cholestasis.
 Gamma glutamyl transferase (γ-GT) level is increased in
obstructive jaundice.
 Its level is a sensitive biomarker of alcohol abuse or
alcoholic liver disease.
 5-nucleotidase enzyme is increased in hepatobiliary
disease.

24. 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.

25.  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
due to secondary rise is diagnostic of Dubin
Johnson syndrome.

26. Physiological Classification
Blood – Bili-Alb
decreased uptake – Gilbert syndrome
Hepatocyte – Bili
decreased conjugation
Neonatal J
UDP-Glu.a Toxic J – Chloroform, CCl4, para
Crigler-Najjar syndrome
Gilbert syndrome.
Bilirubin Diglucuronide
decreased secretion
Dubin- Johnson syndrome.
Rotor synd.
Bileduct – Bilirubin Diglucuronide

27. 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

28. Flow Chart - Jaundice
J (suspected)
History
Clinical examination
VD Berg test
Sr.Bili. – Total/Difference (CHB/UCHB)
Total Bili. Increased Total bili. Increased
UCHB increased CHB increased
VD Berg test VD Berg test
(indirect +ve) Direct +ve
Hemo Jaundice Obst. J. + HC.J

29. Obst. J+ HC.J
Sr.ALP (Crucial test)
>35 <35
?. Obst.J HC.J
1. Sr.Trans (<300) Sr.Trans. (>300)
2. Sr.ALP increased Sr.GGT increased
3. PT after iv vit.k – normal PT even after vit.k
abnormal
4. Urine – bilirubinuria Urine – bili. + or -
5. Urobilinogen – neglibile Serological tests
or absent

30. Bio-Chem tests
Lab tests – determined severity of J
Its type whether obstructive or HC
1. Vanden Berg reaction
- direct
- indirect
2. Bilepigments in urine
- may be detected even before clincial jaundice
is noticed
- bili is found in urine – Obstr. Jaundice
- not found in urine – hemolytic jaundice
3. Feces – bili is not found in normal
Found in children, neo mycin, meconiun

31. 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