Liver function tests assess the functioning of the liver and include measurements of bilirubin, liver enzymes, protein and coagulation factors. Bilirubin, albumin, ALT, AST and ALP are elevated in hepatic jaundice, while ALP, GGT, 5'NT and bile salts are higher in obstructive jaundice. The tests help differentiate between hepatocellular damage and obstructive liver disease and determine the underlying cause of jaundice. Prothrombin time is prolonged in both hepatic and obstructive jaundice.

1. Liver Function Tests

2. Definition of LFT
• These are a group of biochemical investigations done to
assess the functioning of the liver.
• Indications:
• 1. Patients with hepatitis, jaundice( to know the type of
jaundice)
• 2. to know the severity of liver disease
• 3. before chemotherapy
• 4. when patients are on drugs which affect liver
• 5. As a routine before surgery

3. LFT
• In clinical practice, LFT includes
• Serum bilirubin – total & direct
• Enzymes( ALT, AST and ALP)
• Total protein / Albumin
• Prothrombin time
• To investigate a case of jaundice: urine & stool
tests are also done
• For diagnosis of viral hepatitis, serology is
done

4. I. Tests based on excretory functions of
liver
a. Serum Bilirubin estimation
b. Urine bile pigment
c. Urine bile salts
d. Urine Urobilinogen

5. a. Serum Bilirubin
• Normal Total - 0.2 – 0.8 mg%
• Unconjugated – 0.2 – 0.6 mg%
• Conjugated – 0 – 0.2 mg%
• > 1mg /dl– Latent jaundice
• > 2mg/dl – Jaundice – yellow
discoloration of skin, sclera & mucous
membrane

6. II. Tests based on synthetic functions of
liver
a. Serum Albumin –
- almost all plasma proteins except Ig
synthesized by liver
- Albumin quantitatively most important –
reflects extent of functioning liver cell mass
- Half life – 20 days – so albumin ↓ in all
chronic diseases of liver

7. • Total protein – 6 - 8 g%
• Albumin - 3.5 – 5 g%
• Globulin - 2.5 – 3.5 g%
• A : G ratio - 1.2 : 1 to 1.5 : 1
• A : G reversal – liver cirrhosis –
hypoalbuminemia with compensatory
hypergammaglobulinemia
• Albumin < 2g% - edema all over body

8. • B. Prothrombin time (PT)
• Factors II,VII,IX and X are synthesized by liver
• Half life 6hrs – indicates present function of
liver: Rise in acute liver injury.
• PT prolonged in Hepatocellular & Obstructive
Jaundice

9. IV. Liver Enzyme Panel
A. Markers of Hepatocellular damage
- Alanine Amino Transferase (ALT)
- Aspartate Amino Transferase (AST)
B. Markers of obstructive liver disease
- Alkaline Phosphatase (ALP)
- Gamma Glutamyl Transferase (GGT)
- 5’ Nucleotidase / Nucleotide phosphatase
(5’NT)

10. A. Markers of hepatocellular damage
• ALT – 13 - 35 IU/L
• AST - 8 – 20 IU/L
• Very high values > 1000 IU/L seen in acute
hepatitis – both viral & toxic
• Moderate rise (100-300 IU/L) in Wilson’s
disease, non-alcoholic chronic hepatitis
• Minor rise (<100 IU/L) in Hepatitis C, fatty
liver

11. B. Markers of obstructive liver disease
• ALP : (40 – 125 IU/L)
• Synthesized by cells lining biliary canaliculi.
Obstruction of bile causes irritation of cells
leads to secretion of ALP into serum
• Very high values (10-12 times the upper
normal limit ) in Extra hepatic obstruction –
gall stones or pressure on bile duct by cancer
of head of pancreas

12. • moderate rise (2-3 times) - In hepatic diseases
– hepatocellular carcinoma , alcoholic
hepatitis
• But in later stages of hepatitis, inflammatory
edema – obstructive phase – ALP ↑
• In neoplasms of liver, Regan isoenzyme ↑
• ALP ↑ in bone diseases (bone form)

13. • GGT - 10 – 30 IU/L
• Marker enzyme for alcohol abuse
• In liver diseases GGT rise parellels that of ALP
• Also in pancreatic disease, prostate cancer

14. • 5’ NT - 2 – 10 IU/L
• Very high in biliary obstruction.
• Moderate rise in hepatitis
• More specific for obstructive liver disease
since not increased in childhood or
pregnancy

16. Laboratory findings in Jaundice
Enzyme
Estimation
Hemolytic
Jaundice
Hepatic
Jaundice
Obstructive
Jaundice
Serum ALP
(40-120
IU/L)
N ↑ 2-3 times ↑ ↑ ↑ (10-12
times of
upper normal
in
extrahepatic
obstruction)
Serum AST
& ALT
N ↑ ↑ ↑ moderate ↑
Serum 5’ NT N moderate ↑ ↑ ↑ ↑

17. Laboratory investigations in Jaundice
Hemolytic
Jaundice
Hepatic
Jaundice
Obstructive
Jaundice
Prothrombin
time ( PT)
N Prolonged Prolonged
A:G ratio N Decreases as
albumin levels
decrease
N

18. Laboratory investigations in Jaundice
Hemolytic
Jaundice
Hepatocellular
Jaundice
Obstructive
Jaundice
Urine bile
salts
Absent ↑↑ ↑↑
Urine
Bilirubin
Absent ↑↑↑ ↑↑↑
Urine UBG ↑↑ N or ↓ ↓ or Absent
Fecal SBG ↑↑ N or ↓ ↓ or Absent
(clay colored