This document discusses liver function tests. It classifies tests based on laboratory findings and clinical aspects. Key tests include bilirubin to measure excretory function, albumin and prothrombin time to measure synthetic function, and ALT/AST to measure hepatocellular injury. Alkaline phosphatase and GGT indicate obstructive liver disease or cholestasis. Normal ranges are provided for important tests like bilirubin, ALT, AST, alkaline phosphatase. Methods for measuring bilirubin and calculating A:G ratio are also outlined.

1. LIVER FUNCTION TESTS
ADARSH BENNY

2. Classification of liver function tests
A. Classification based on laboratory findings
Group I (Tests of hepatic excretory function)
i. Serum – Bilirubin; total, conjugated, and unconjugated.
ii. Urine – Bile pigments, bile salts and urobilinogen
Group II: Liver enzyme panel
o Alanine amino transferase (ALT)
o Aspartate amino transferase (AST)
o Alkaline phosphatase (ALP)
o Gamma glutamyl transferase (GGT)

3. Group III: Plasma proteins (Tests for synthetic function of liver)
i. Total proteins
ii. Serum albumin, globulins, A/G ratio
iii. Prothrombin time
Group IV: Special tests
i. Ceruloplasmin
ii. Ferritin
iii. Alpha-1-antitrypsin (AAT)
iv. Alpha-fetoprotein (AFP)

4. • B. Classification based on Clinical aspects
Group I: Markers of liver dysfunction
• i. Serum bilirubin, total, conjugated
• ii. Urine: Bile pigments, bile salts and UBG
• iii. Total protein, serum albumin and A/G ratio
• iv. Prothrombin time v. Blood ammonia, when indicated
Group II: Markers of hepatocellular injury
• i. Alanine amino transferase (ALT)
• ii. Aspartate amino transferase (AST)
Group III: Markers of cholestasis
• i. Alkaline phosphatase
• ii. Gamma glutamyl transferase

5. I. Test for excretory function of liver
1) Bilirubin
• Normal range
• Serum total bilirubin; 0.2 to 0.8 mg/dl
• unconjugated bilirubin ; 0.2–0.6 mg/dl
• conjugated bilirubin; 0–0.2 mg/dl
• serum bilirubin above 1 mg/dl is hyperbilirubinemia
• Bilirubin level goes above 2 mg/dl is termed as jaundice

6. 2) Urinary bilirubin
•bile pigments are Measured by fouchet’s test
3) Urobilinogen
•urobilinogen is measured by Ehrlich's test
4) Urine Bile Salts
•Bile salts in urine are detected by Hay’s test

7. II. Tests based on Synthetic Function of Liver
• Total proteins
• Almost all the plasma proteins except immunoglobulins are
synthesised by the liver.
• Normal albumin level in blood is 3.5 to 5 g/dl; and globulin
level is 2.5 to 3.5 g/dl.

8. • Prothrombin time (PT)
• Since prothrombin is synthesised by the liver, it is a
useful indicator of liver function
• In case of liver disease, the PT remains prolonged

9. III. Tests based on Serum Enzymes (Liver
Enzyme Panel)
• Enzymes indicating hepatocellular damage (AST &ALT)
• Normal serum ALT (alanine amino transferase) is 10-35 U/L
• Normal serum AST level is 10-40 U/L
• The levels of ALT and AST in serum are elevated in all liver
diseases
• Very high levels (more than 1000 units) are seen in acute
hepatitis (viral and toxic)
• Elevation of ALT is more in cases of hepatic disease
compared to AST

10. Markers of Obstructive Liver Disease
• Alkaline Phosphatase (ALP)
• Very high levels of alkaline phosphatase (ALP) are seen in
patients hepatic carcinoma
• Very high levels of ALP (10-12 times of upper limit) may be
noticed in extrahepatic obstruction (obstructive jaundice)
caused by gallstones
• Drastically high levels of ALP (10-25 times of upper limit) are
seen in bone diseases , Paget's disease , rickets,
osteomalacia.
• Normal level; 40-120 U/L

11. • Gamma Glutamyl Transferase (GGT)
• GGT is clinically important because of its sensitivity to
detect alcohol abuse.
• Elevated levels of GGT are observed in chronic
alcoholism

12. Special tests
• Ceruloplasmin (Cp)
• It is mainly synthesized by the liver
• Level of Cp is decreased in liver disease
• a1- anti trypsin
• synthesized in liver
• Low levels are seen in emphysema

13. iv. Test based on detoxification function
1. Blood ammonia
• ammonia is converted to urea by the liver, but this
activity is considerably decreased in hepatic cell damage.
v. Test on the Metabolic Capacity of Liver
1. galactose
• Galactose is converted to glucose by liver
• In liver disease, galactose level increases

14. • The bilirubin is estimated by van den Bergh reaction
• diazotised sulfanilic acid (sulfanilic acid in HCl and sodium nitrite)
reacts with bilirubin to form a purple-colored complex,
azobilirubin. Normal serum does not give a positive van den
Bergh reaction
• When bilirubin is conjugated, the purple color is produced
immediately on mixing with the reagent, the response is said to
be van den Bergh direct positive.
• When the bilirubin is unconjugated, the color is obtained only
when alcohol is added, and this response is known as indirect
positive

15. • If both conjugated and unconjugated bilirubins are
present in increased amounts, a purple color is
produced immediately and the color is intensified on
adding alcohol. Then the reaction is called biphasic

16. • A:G ratio
• Normal range: 1.2:1 – 2:1
• Decreased A:G ratio is either due to decrease in albumin or increase in
globulins
• It is seen in
• Decreased synthesis of albumin
• Excretion of albumin in urine
• Increased production of hlobulin