Liver Function Tests (LFT)

Review: Liver

The liver is the largest organ in the body. It is located below the diaphragm in the right

upper quadrant of the abdominal cavity and extended approximately from the right 5th rib to the lower border of the rib cage.

The working cells of the liver are known as hepatocytes.

Liver regeneration can occur after surgical removal of a portion of the liver or after injuries that destroy parts of the liver.

Functionally Complex Organ that place a critical biochemical role in- Metabolism – Digestion – Detoxification and Elimination of substance from body.

Based on functional capabilities of organs specific biochemical investigation have been developed to assess their functions.

FUNCTIONS OF LIVER

Metabolic function: Liver actively participates in

carbohydrate, lipid, protein, mineral & vitamin metabolisms.

Excretory function: Bile pigments, bile salts & cholesterol

are excreted in bile into intestine.

Hematological function: Liver participates in formation of blood

(particularly in embryo) Liver is also produces clotting factors

like factor V, VII. Fibrinogen involved in blood coagulation

is also synthesized in liver. It synthesize plasma proteins &

destruction of erythrocytes.

Storage function: Glycogen, vitamins A, D & B12 & trace

element iron are stored in liver. Protective function & detoxification: Ammonia is detoxified to urea. kupffer cells of liver perform

phagocytosis to eliminate foreign compounds.

Liver is responsible for the metabolism of xenobiotics.

! Why is LFT (liver function test) done?

Detect presence of liver disease

To Detect the disease whether mild or Severe

Distinguish among different types of liver diseases.

Follow the response of treatment

DIFFERENT TESTS TO ASSESS LIVER FUNCTION

1. ABNORMALITIES OF PIGMENT METABOLISM

*serum bilirubin and van den berg reaction*urine bilirubin*urine and faecal urobilinogen

2. TESTS BASED ON LIVER PART IN CARBOHYDRATES METABOLISM* galactose tolerance test* fructose tolerance test

3. TESTS BASED ON CHANGE IN PLASMA PROTEINS* determination of plasma protein-albumin, globulin fibrinogen

4. TESTS BASED ON ABNORMALITIES OF LIPIDS* determination of serum cholesterol and the proportion of free and ester cholesterol

5. TESTS BASED ON THE DETOXICATING FUNCTION OF LIVER* hippuric acid synthesis test

6.TESTS BASED ON EXCRETORY FUNCTION OF LIVER* bromosulpthalein test

7. FORMATION OF PROTHROMBIN BY LIVER* determination of prothrombin time

8. DETERMINATION OF BIOOD AMMONIA

9. DETERMINATION OF SERUM ENZYME ACTIVITIES

* aspartate transaminase* alanine transaminase* alkaline phosphatase* 5-nucleotidase* gamma glutamyl transferases* lactate dehydrogenase

1. TESTS BASED ON ABNORMALITIES OF BILE PIGMENT METABOLISM

SERUM BILIRUBIN

* bilirubin is excretory end product of heme degradation.* conjugated by liver to form bilirubin di glucuronide and excreted through bile.o Normal conc. of serum bilirubin ----0.2 to 0.8mg/dl.o Conjugated bilirubin--- 0.1 to 0.4mg/dl.o Unconjugated bilirubin--- 0.2 to 0.9mg/dl

# Increased total bilirubin (TBIL) causes jaundice , and can indicate a number of problems.

Van den Bergh Test for Bilirubin It is a specific test for for identificaion of increased serum

bilirubin levels. Normal serum gives a negative van den Bergh reaction. Mechanism of the reaction: Van den Bergh reagent is a mixture of equal volumes of sulfanilic acid (in dilute HCI)& sodium nitrite. Principle: Diazotised sulfanilic acid reacts with bilirubin to form a purple coloured azobilirubin.

Direct and indirect reactions: Unconjugated Bilirubin is insoluble in water while the conjugated bilirubin is soluble.

Van den Bergh reagent reacts with conjugated bilirubin & gives a purple colour immediately (normally within 30 seconds).

• This is DIRECT POSITIVE van den Bergh reaction. Addition of methanol (or alcohol) dissolves the

unconjugated bilirubin & gives the van den Bergh reaction (normally within 30 minutes) positive.

• This is INDIRECT POSITIVE. lf the serum contains both unconjugated and conjugated

bilirubin in high concentration, the purple colour is produced immediately (direct positive) which is further intensified by the addition of alcohol (indirect positive).

• This type of reaction is known as BIPHASIC.

JAUNDICE Yellowish discoloration of the skin , eyes , and mucous

membrane due to increased bilirubin level. # Jaundice is visible when serum bilirubin exceeds 2.4 mg/dl.There are 3 TYPES of jaundice:-

1.PREHEPATIC/HAEMOLYTIC2.HEPATIC/HEPATOCELLULAR3.POST HEPATIC/OBSTRUCTIVE

*HAEMOLYTIC JAUNDICE—increases in unconjugated bilirubin—van der Bergh test is indirect reaction*HEPATOCELLULAR JAUNDICE —increases either or both --- Van der Bergh testis direct reaction*OBSTRUCTIVE JAUNDICE—increases in conjugated bilirubin—Van der Bergh test is direct reaction

Van den Bergh reaction & jaundice

It is useful in understanding the nature of jaundice. This is due to jaundice is characterized by increased

serum concentration of unconjugated bilirubin (hemolytic), conjugated bilirubin (obstructive) or both of them (hepatic).

Indirect positive - Haemolytic jaundice Direct positive - Obstructive jaundice Biphasic - Hepatic jaundice

Urinary Bilirubin # Normally bilirubin is absent in urine. Unconjugated bilirubin is insoluble in water and always

absent in urine Conjugated bilirubin being water soluble is excreted in urine in obstructive jaundice. This can be detected by Fouchet’s test

Urinary urobilinogen: # Normally trace amounts is present in urine. In obstructive jaundice no urobilinogen is present in urine

because bilirubin cannot enter intestine.Note: Presence of bilirubin in urine and absence of urobilinogen

in urine is seen in obstructive jaundice. In hemolytic jaundice increased production of bilirubin

causes increased formation of urobilinogen which appears in urine.

Note: Increased urobilinogen in urine and absence of bilirubin in urine is seen in hemolytic jaundice.

Fecal urobilinogen# Normally urobilinogen in faeces is excreted is 50-

250mg/day.

In Hemolytic jaundice faecal urobilinogen is increased which is dark colored.

In Obstructive jaundice faecal urobilinogen is decreased or absent; as there is obstruction in flow of bile and the color of the feces is pale or clay-colored.

A complete absent of faecal urobilinogen shows malignant obstruction.

A decrease may also occur in extreme cases of diseases affecting hepatic parenchyma.

2. TESTS BASED ON LIVER PART IN CARBOHYDRATE METABOLISM

GALACTOSE TOLERANCE TEST Galactose is monosaccharide exclusively metabolized by the liver.* The liver function can be assessed by measuring the utilization of galactose* The normal liver is able to convert galactose into glucose ;but this function is impaired in intrahepatic disease and the amount of blood galactose and galactose in urine is excessive.Method:• subject is given galactose intravenously about 300mg/kg body

weight.• blood is withdrawn at 10mins intervals for 2hrs,galactose is

estimated.Interpretations:• normally, half life of galactose is about 10-15mins.• this is markedly increased in hepatocellular damage (cirrhosis,

infective hepatitis)

3. TESTS BASED ON CHANGES IN PLASMA PROTEIN

DETERMINATION OF TOTAL PLASMA PROTEIN ALBUMIN,GLOBULIN & A:G RATIO

• Liver is the site of albumin synthesis and also possibly of some α and β globulin.

• Albumin has a half-life of 20-25 days. It is a good marker to assess chronic liver damage.

• Albumin is also decreased in malnutrition.• In advanced parenchymal liver disease and in cirrhosis liver

albumin is grossly decreased and globulin are often increases .So that A:G ratio is reversed.

• Total plasma protein conc.--- 6.0 to 8.0g/dl• Albumin level --- 3.5 to 5.3 g/dl• Globulin level --- 2.5 to 3.5 g/dl

4. TESTS BASED ON ABNORMALITIES OF LIPIDS

CHOLESTROL-CHOLESTERYL ESTER RATIO: The liver plays an important and active role in the

metabolism of cholesterol including its synthesis , esterification, oxidation and excretion.

Interpretations: Normal total blood cholesterol ranges 150 to 250mg/dl

and abt 60-70% in esterified form. In obstructive jaundice, total blood cholesterol level is

increased and the esterified form is also increased. In liver damage, no change in total blood cholesterol level

but its esterified form is decreased. In severe acute hepatic necrosis, total blood cholesterol

level is decreased upto 100mg/dl and there is marked reduction in % present as esters.

5. TESTS BASED ON DETOXICATING FUNCTION OF THE LIVER

HIPPURIC ACID SYNTHESIS

The liver is the major site for the metabolism of xenobiotic (detoxification).

Measurement of hippuric acid synthesis is an ideal test for assessing the detoxification function of liver.

Hippuric acid is produced in the liver when benzoic acid combines with glycine.

6gm sodium benzoate(given orally dissolved in water after light breakfast)

yield 7.5gm of hippuric acid. In healthy person, 60% of sodium benzoate is excreted in

urine. A reduction in hippuric acid excretion ( <3g) hepatic damage

6. TESTS BASED ON EXCRETORY FUNCTION OF LIVER

BROMOSULPHTHALEIN Bromosulphthalein is a dye used to assess the excretory function of liver. It is a non-toxic compound & excreted by the liver (through bile). In normal individual, a constant proportion (10-15% of dye) is removed per

minute.Method: BSP is administered intravenously (5 mg/kg body weight) in overnight fasting

patient. Its serum concentration is measured at 45 min & at 2 hrs.Interpretations: In normal individuals, <5% of the dye is retained at the end of 45 min. In liver damage, retention process is slow and 40-50% of dye is retained in

45min sample.

7. FORMATION OF PROTHROMBIN BY LIVER

The liver synthesizes all the factors concerned with blood clotting. A decrease in the concentration of plasma clotting factors is found in

the impairment of liver function. Prothrombin time is prolonged in patients with liver damage,

compared to normal. Normal : 10-16 sec Prolongation of Prothrombin Time by 2 sec / more – Abnormal PT – factors II,V, VII, X Half life 6 hrs – factor VII , 5 days – fibrinogen Prothrombin Time prolonged – hepatitis, cirrhosis, vitamin K

deficiency ( obstructive jaundice, fat malabs )

8. DETERMINATION OF BIOOD AMMONIA

The major source of ammonia(NH3) in blood is bacteria of gastrointestinal tract(GIT).

Ammonia is later converted to urea by the liver then it is excreted by kidneys.

This test used for detecting hepatic encephalopathy.

Normally, blood ammonia varies from 40-75μg/ 100ml of blood.

Increased in ammonia in blood is found in cases of cirrhosis of liver .

In liver damage, blood ammonia levels may be >200μg/100ml .

7. SERUM ENZYMES – REFLECT DAMAGE TO HEPATOCYTES

A large number of enzyme estimations are available which are used to ascertain liver function.

They are be divided into two groups: A). Enzymes indicating hepatocellular damage. B). Enzymes indicating cholestasis (obstruction). In liver cells injury , damage to the membrane of

cells & organelles allows intracellular enzymes to leak into the blood

A) Enzymes indicating hepatocellular damage

AST (aspartate transaminase)/SGOT (serum glutamate oxaloacetate transaminase)

ALT (alanine transaminase)/SGPT (serum glutamate pyruvate transaminase)

SGOT

SGPT

Aspartate transaminase (AST/SGOT)

Normal range: 10-45 U/L. AST is found in both cytoplasm &

mitochondria AST/GOT also reflects damage to the hepatic

cells & is less specific for liver disease. It is a cardiac marker. AST help diagnose various heart, muscle or

brain disorders, such as a myocardial infarct (heart attack).

Elevated levels of AST may indicate

Acute hemolytic anemia Cirrhosis of the liver Hepatitis Acute pancreatitis or inflammation of

pancreas Acute renal failure or loss of kidney function. Heart attack Primary muscle disease Recent surgery

Alanine transaminase (ALT/SGPT) Normal Range: 5-40 U/L. ALT is a cytoplasmic enzyme. The activity of these enzymes is low in

normal serum. ALT is specific for liver disease. Its elevations favor liver cell necrosis as

a cholestasis.

Elevated levels of ALT/SGPT may indicate

Alcoholic liver disease Cancer of liver Hepatitis or inflammation of the liver Noncancerous tumor of the liver Use of medicines or drugs toxic to the liver Cirrhosis or scarring of the liver Death of liver tissue.

B) Enzymes indicating cholestasis

1) ALP(alkaline phosphatase) ALP occurs in in all tissues, especially liver, bone, bile duct, kidney & the

placenta. The ALP used to help diagnose certain liver diseases and bone disorders. Normal range: 30 - 95 IU/L (3-13 kings unit) ALP is a hydrolase enzyme responsible for removing phosphate groups

from many types of molecules, including nucleotides & proteins. Most effective in an alkaline environment. Levels are significantly higher in growing children. A rise in serum ALP (normal 3-13 KA units/dl), usually associated with

elevated serum bilirubin is an indicator of biliary obstruction (obstructive/post hepatic jaundice).

ALP is also elevated in cirrhosis of liver & hepatic tumors.

2) γ - Glutamyl transpeptidase (GGT)

Normal range: 10-15 U/L This is a microsomal enzyme widely distributed in body tissues,

including liver. Measurement of γ - glutamyl transpeptidase (GGT) activity

provides a sensitive index to asses liver abnormality. Serum GGT is highly elevated in biliary obstruction & alcoholism. GGT elevation parallels than of ALP. Increased level of GGT are observed in chronic

alcoholism ,pancreatic disease ,MI ,renal failure ,diabetes mellitus. Several drugs (e.g. phenytoin) induce (liver synthesis) & increase

this enzyme in circulation.

3). 5'-Nucleotidase

Normal range: 2-15 U/L The serum activity of 5'-nucleotidase is elevated

in hepatobiliary disease & this parallels ALP. It is highest in post-hepatic obstructive jaundice. The 5'-nucleotidase is normal in patients with

bone disease where as serum ALP increased .

Thank you