Liver function tests (LFTs) assess the health of the liver by measuring certain proteins and enzymes. LFTs can help diagnose liver disease, monitor treatment, and assess prognosis. They test the liver's metabolic, secretory, excretory, storage, detoxifying, and synthetic functions. Specific tests include bilirubin to assess conjugation/excretion, albumin and prothrombin time to evaluate synthesis, and AST/ALT to detect cellular damage. Elevations in certain enzymes or proteins indicate conditions like hepatitis, cirrhosis, or blockages of the bile ducts. LFTs are important for understanding liver function and identifying underlying liver issues.

1. Liver Function Tests
DR. FARHANA ATIA
ASSOCIATE PROFESSOR
DEPARTMENT OF BIOCHEMISTRY
NILPHAMARI MEDICAL COLLEGE, NILPHAMARI

2. Liver Function Tests
LFT or liver panel are a
group of tests that help in
Diagnosis of liver disease,
monitor therapy &
assess prognosis of liver
disease

3. Functions of liver
Metabolic
Secretory- lipid, VLDL
Excretory- Bilirubin
Storage- Fat soluble vitamins, Vit-B12, Fe,
Carbohydrates
Detoxifying- Drug
Synthetic- Plasma protein, clotting factor

4. Liver Function Tests
Test Function assessed Utility
1. Serum bilirubin
(total &
conjugated)
Conjugation &
excretory function
D/D of jaundice
2. Total serum
protein & albumin
Biosynthetic function Indicator of severity of
chronic liver disease
3. Prothrombin
time
Biosynthetic function Indicator of severity of
acute liver disease

5. Liver Function Tests
Test Function assessed Utility
4. Serum
enzymes
 AST, ALT
 ALP, GGT
 Hepatocellular
integrity
 Biliary obstruction
• Early indicator of
damage
• Cholestasis
5. Blood
ammonia
Detoxification • ↑ in cirrhosis of liver
with portal
hypertension
• Disorder in urea cycle

6. Test for Synthetic Function
Total Plasma Protein- 6.0-8.3 g/dl 60-83 g/L
Serum albumin- 3.4-5.4 g/dl
Albumin is solely synthesized by liver
Half life is 3wks (20-25 days)
Low level indicates chronic liver disease, malnutrition
Immunoglobulin is not synthesized in liver. So A/G
ratio is altered in liver disease

7. Test for Synthetic Function
Half life of Prothrombin is 5-72 hours
In liver disease there are decreased of plasma clotting
factors
Assessed by lab by PT
PT is prolonged in liver damage (Acute LD, also in
chronic disease
Vitamin K (required for factor II, VII, IX, X) deficiency
should be ruled out by measuring prothrombin time
before & after vitamin K administration

8. Bilirubin Metabolism
 After ≈120 days in the circulation,
RBC are taken up and degraded by the
mononuclear phagocyte system (MPS), particularly in
the liver & spleen
Breakdown of heme to bilirubin in macrophages
Unconjugated bilirubin (complexed to albumin) is
transported through the blood to the liver

9. Bilirubin Metabolism
 Bilirubin is taken up
via facilitated diffusion
by the hepatocyte &
conjugated with
glucuronic acid to form
bilirubin diglucuronide

10. Bilirubin Metabolism
Conjugated bilirubin is
actively secreted into bile
and then the intestine
In the intestine,
glucuronic acid is removed
by bacteria. The resulting
bilirubin is converted to
urobilinogen

11. Bilirubin Metabolism
 Some of urobilinogen is reabsorbed
from the gut & enters the portal blood
A portion of urobilinogen participates
in the enterohepatic urobilinogen cycle
The reminder is transported by the
blood to the kidney, where it is
converted to yellow urobilin & excreted,
giving the urine its characteristic color
Urobilinogen

12. Bilirubin Metabolism
Urobilinogen is oxidized by
intestinal bacteria to brown
stercobilin

13. Plasma Bilirubin
Normal : 0.2–0.8 mg/dl
Unconjugated bilirubin: 0.2–0.6 mg/dl
Conjugated bilirubin: 0–0.2 mg/dl
Hyperbilirubinemia: >1mg/dl
Latent jaundice: 1 - 2 mg/dl
Clinical jaundice: > 2 mg/dl

14. Terminology
Jaundice: Refers to the yellowish discoloration of sclera, conjunctiva,
skin & mucous membrane due to deposition of bilirubin secondary to
hyperbilirubinemia
Icterus: Greek term for jaundice
Kernicterus: Bilirubin encephalopathy. It is a neurological syndrome
resulting from destruction of basal ganglia by deposition of bile pigment
in severe hemolytic anemia specially in premature infant whose BBB is
underdeveloped

15. Classification of Jaundice
Hemolytic
(prehepatic)
• Hemolysis/ abnormal
RBC
• Antibodies
• Drugs & toxins
• Thalassemia
• Hemoglobinopathies
Hepatocellular
(hepatic)
• Viral hepatitis
• Toxic hepatitis
• Intrahepatic
cholestasis
• Gilbert's syndrome
• Criglar-Najjar
syndrome
Obstructive
(posthepatic)
• Extrahepatic
cholestasis
• Gall stone
• Tumors of bile duct
• Carcinoma head of
the pancreas
• Carcinoma ampulla
of Vater

16. Jaundice Hemolytic
(prehepatic)
Hepatocellular
(hepatic)
Obstructive
(posthepatic)
Underlying
condition
Overproduction
of bilirubin
Decreased
conjugation of
bilirubin
Obstruction of
common bile duct
(extrahepatic
cholestasis
Total bilirubin Increased Increased Increased
Conjugated
bilirubin
Normal Increased Increased
Unconjugated
bilirubin
Increased Increased Normal

17. Jaundice Hemolytic
(prehepatic)
Hepatocellular
(hepatic)
Obstructive
(posthepatic)
Urobilinogen Increased Increased Absent
Urine color Normal Dark (urobilinogen
+ conjugated
bilirubin)
Dark (conjugated
bilirubin)
Stool color Normal Normal/ Pale Pale
Conjugated
bilirubin in urine
Not present Present Present
ALT/ AST Normal Increased Normal
ALP Normal Normal Increased

18. Thank You