Liver Function Tests (LFT)

Synthetic functions : synthesis of plasma proteins, cholesterol, triacyl glycerol, lipoprotein

Metabolic function: protein metabolism, ketogenesis, TCA cycle, production of ATP

Detoxification & excretion: ammonia to urea, bilirubin, cholesterol, drug metabolites.

Homeostasis : blood glucose regulation Storage function: Vitamin A,D,K,B12 Production of bile salts

Functions of liver

Screening: They are non invasive yet sensitive modality for liver dysfunction.

Pattern of disease: They are helpful to recongnize pattern of various diseases. Like being helpful in differentiating between acute viral hapatitis and various cholestatic disorders and chronic liver disease.(CLD)

Assess severity : They are heplful to assess the severity and predict the outcome of certain diseases like primary biliary cirrhosis.

Follow up: They are helpful in the follow up of certain liver diseases and also helpful in evaluating response to therapy like autoimmune hepatitis

USES OF LFT

Classification of liver function tests 1. Tests of the liver’s capacity to transport organic

anions & to metabolise drugs-serum bilirubin, urine bilirubin, urobilinogen etc.

2. Tests that detect injury to hepatocytes (serum enzyme tests)- Aminotransferases, Alkaline phosphatase, glutamyl transpeptidase,5nucleotidase,leucine aminopeptidase etc.

3. Tests of the liver’s biosynthetic capacity-serum proteins, albumin, ceruloplasmin, prothrombin time etc.

Jaundice Suspected liver metastasis Alcoholic liver disease Any undiagnosed chronic illness Annual checkup of diabetic patients Coagulation disorders Therapy with statins to check

hepatotoxicity

Indications for the liver function tests

TEST OF THE LIVER’S CAPACITY TO TRANSPORT ORGANIC ANIONS AND TO METABOLIZE DRUGS

BYADITYA GIRI

Serum bilirubin .Bilirubin is an endogenous anion derived from

catabolism of heme.

. It is conjugated by liver to form bilirubin levels ,more than 17umol/L suggests liver disease.

.Classification of bilirubin into direct & indirect bilirubin is based on original van den bergh method of measuring bilirubin.

.Van den Bergh is a chemical reaction used to measure bilirubin level in blood. The reaction is highly useful in understanding the nature of jaundice.

Bilirubin metabolism.Bilirubin is the excretory product formed by the

catabolism of heme part of haemoglobin..Porphyrin part of heme are converted to bilirubin in

reticuloendothelial cells of liver, spleen, bone marrow.

.Unconjugated bilirubin is bound to serum albumin & transferred to liver where it is conjugated to glucuronate by UDP GLUCURONYL TRANSFERASE.

.Conjugated bilirubin is excreted into bile. A fraction of bilirubin from stool is reabsorbed into blood via portal circulation (enterohepatic circulation).

PRODUCTION & EXCRETION OF URINE

PRINCIPLE: When diazotised sulfanilic acid reacts with bilirubin, it forms ‘azobilirubin’ which is a purple colour product.

. Increased conjugated bilirubin – gives colour immediately i.e direct positive.

.Increased unconjugated bilirubin -gives colour only after addition of methanol i.e indirect positive

SERUM BILIRUBIN- ESTIMATION(VAN DEN BERGH TEST FOR BILIRUBIN)

Hyperbilirubinemia : when the level of bilirubin exceeds 1mg/dl in serum.

Based on the cause it is classified into congenital and acquired.

Congenital hyperbilirubinemia: They result from abnormal uptake, conjugation or excretion of bilirubin due to inherited defects

CRIGLER-NAJJAR SYNDROME: Here the defect is in conjugation due to severe deficiency of enzyme UDP-GLUCURONYL TRANSFERASE. Unconjugated bilirubin level increases to more than 20mg/dl and hence kernicterus occurs.

GILBERT SYNDROME: it is inherited as an autosomal dominant trait. The defect is in the uptake of bilirubin by the liver . Bilirubin level goes around 3mg/dl.

DUBIN-JOHNSON SYNDROME: It is an autosomal recessive trait leading to defective excretion of conjugated bilirubin, so conjugated bilirubin in bold increases. There is defect in transport of conjugated bilirubin into bile. Bilirubin gets deposited in the liver and liver appears black. This condition is known as black liver jaundice.

ROTOR SYNDROME: It is an autosomal recessive trait. In this bilirubin exrection is defective.

PHYSIOLOGICAL JAUNDICE: Also known as neonatal jaundice. This transient hyperbilirubinemia is due to an accelerated rate of destruction of RBCs & also because of immature hepatic system of conjugation of bilirubin. In all new born infants after the 2nd day of life, mild jaundice appears. In such cases bilirubin does not increase above 5mg/dl.

BREAST MILK JAUNDICE: In some breast-fed infants, prolongation of jaundice has attributed to high level of estrogen derivative in maternal blood, which is excreted through the milk. This would inhibit the glucuronyl transferase system .Sulfa and other drugs may release bilirubin from albumin and may cause jaundice in new born.

ACQUIRED HYPERBILIRUBINEMIA

CLINICAL MANIFESTATIONS OF LIVER DYSFUNCTION JAUNDICE :-Jaundice is the yellowish discolouration of sclera, skin, mucous membrane. It is characteristic of liver disease but will occur when rate of hemolysis is increased leading to the elevation of serum albumin.

HEMOLYTIC JAUNDICE Hemolytic disease of newborn: Rh incompatibilty – Erythroblastosis fetalis

Hemolytic diseases of Adults: condition is seen in increased rate of hemolysis. It usually occurs in adults. There is increase in unconjugated bilirubin in blood, absence of bilirubinuria & excessive excretion of UBG in urine & SBG in feces.

HEPATOCELLULAR OR HEPATIC JAUNDICE

.The most common cause is viral hepatitis, caused by hepatitis viruses A,B,C,D or E.

.In pure hepatocellular disease, conjugation in liver is decreased leading to increase in free bilirubin in circulation.

.The UBG level in urine may be normal or decreased in hepatocellular jaundice.

.In this, a biphasic reaction is observed, because both conj. & unconj. bilirubins are increased

OBSTRUCTIVE OR POSTHEPATIC JAUNDICE .Conjugated bilirubin is increased in blood & it is

excreted in urine. If there is complete obstruction, UBG will be decreased in urine or even absent.

.In total obstruction of biliary tree, the bile doesn’t enter the intestine. Since no pigments are entering the gut, the feces become clay coloured.

.Van den Bergh test is direct positive as conj. bilirubin is elevated.

Types of bilirubin Class of jaundice Causes

Unconjugated Prehepatic or hemolytic Abnormal red cells; antibodies; drugs & toxins; thalassemia; hemoglobinopathies. Gilbert syndrome; Crigler-Najjar syndrome, GPD deficiency.

Unconjugated & conjugated

Hepatic or hepatocellular

Viral hepatitis; toxic hepatitis; intrahepatic cholestasis

Conjugated or obstructive

Posthepatic .Intrahepatic cholestatis-chronic active hepatitis, obstructive stage of viral hepatitis, Dubin- johnson syndrome.Extra hepatic obstruction-stones in the gallbladder or biliary tract, carcinoma of head of pancreas, enlarged lymph glands in the porta hepatis

Hemolytic jaundice

Hepatocellular jaundice

Obstructive jaundice

Blood, free bilirubin

Increased Increased Normal

Blood, conj. Bilirubin

Normal Increased Increased

Blood, ALP Normal Increased Very high Urine, bile salts Nil Nil PresentUrine, conj. Bilirubin

Nil Present Present

Urine bilinogens Increased Present NilFecal urobilinogen

increased Decreased Absent

DIFFERENTIAL DIAGNOSIS OF JAUNDICE

2. URINE BILIRUBIN . The presence of urine bilirubin indicates

hepatobiliary disease. Unconjugated bilirubin is tightly bound to albumin and not filtered by the glomerulus and thus not present in urine. Measurable amount of conjugated bilirubin in serum are found only in hepatobiliary disease.

.Because the renal threshold for conjugated bilirubin is low and the laboratory methods can detect low levels of bilirubin in urine so conjugated bilirubin may be found in urine when the serum bilirubin levels are normal. This is the case in early acute viral hepatitis.

3. UROBILINOGEN . An increase in the urobilinogen in urine is a

sensitive indicator of hepatocellular dysfunction. It is a good indicator of alcoholic liver damage, well compensated cirrhosis or malignant disease of liver. In viral hepatitis it appears early in urine. It is markedly increased in hemolysis.

. In cholestatic jaundice urobilinogen disappears from urine. It is intermittently present in case of gallstones.

.Urobilinogen gives a purple reaction to Ehrlich’s aldehyde reagent.

TEST THAT DETECT INJURY TO HEPATOCYTES

BY AALOK KUMAR

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

SERUM ENZYMES – REFLECT DAMAGE TO HEPATOCYTES

ENZYMES THAT DETECT HEPATOCELLUAR NECROSIS• ALT• AST

ENZYMES THAT DETECT CHOLESTASIS• ALKALINE

PHOSPHATASE• 5 NUCLEOTIDASE• LEUCINE

AMINOPEPTIDASE

TEST BASED ON SERUM ENZYMES

ALKALINE PHOSPHATASE

SERUM TRANSFRASEALT AST

GGT5’NT

ENZYMES IN DIAGNOSIS OF LIVER DISEASE

LOCATION OF ENZYMES IN LIVER

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

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

A) Enzymes indicating hepatocellular damage

SGOT

SGPT

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).

Aspartate transaminase (AST/SGOT)

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

Elevated levels of AST may indicate

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.

Alanine transaminase (ALT/SGPT)

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.

Elevated levels of ALT/SGPT may indicate

• Normal ratio is 0.7 to 1.4

• Useful in Wilson disease, chronic liver disease and alcoholic liver disease

• AST/ALT ratio of > 2:1 is suggestive of and >3:1 is highly suggestive of Alcoholic liver disease

• AST in Alcoholic live disease is rarely >300 IU/L.

• ALT is usually normal in alcoholic liver disease ; can be sometimes low due to an alcohol induced deficiency of pyridoxal phosphate

• AST/ALT <1 is seen in NASH and viral hepatitis.

AST:ALT RATIO

• mAST/total AST ratio – marker of chronic alcohol consumption

• This distinguishes those who consume excess alcohol from normal subjects irrespective of the presence or absence of liver disease

CLINICAL SIGNIFICANCE OF AST:ALT RATIO

ALKALINE PHOSPHATASEY-GLUTAMYL TRANSPEPTIDASE

5-NUCLEOTIDASE

ENZYMES THAT DETECT CHOLESTASIS

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.

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.

1) ALKALINE PHOSPHATASE

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.

2) γ - Glutamyl transpeptidase (GGT)

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 .

3). 5'-Nucleotidase

Function test Pre-hepatic Jaundice Hepatic Jaundice Post-hepatic Jaundice

Total bilirubin Normal / Increased Increased

Conjugated bilirubin Normal Increased IncreasedUnconjugated bilirubin Normal / Increased Increased Normal

Urobilinogen Normal / Increased Increased Decreased / Negative

Urine Color Normal Dark (urobilinogen + conjugated bilirubin)

Dark (conjugated bilirubin)

Stool Color Normal Normal/Pale PaleAlkaline phosphatase levels

Normal

Increased

Alanine transferase and Aspartate transferase levels

Increased

Conjugated Bilirubin in Urine Not Present Present

Splenomegaly Present Present Absent

Table of diagnostic tests

TEST OF LIVER’S BIOSYNTHETIC CAPACITY

BYCHANCHAL KUMAR SAHU

Plasma proteins

Prothrombin time

TESTS BASED ON SYNTHETIC FUNCTION

PROTEIN•Liver is the sole site for synthesis of most plasma proteins except immunoglobulins (gamma globulins)•Serum albumin comprises 60% of all plasma proteins

TESTS FOR PROTEINS INCLUDE-1. Total serum proteins2. Serum albumin3. Albumin/globulin ratio4. Serum protein electrophoresis5. Prealbumin6. Procollagen III peptide7. Ceruloplasmin8. Alpha fetoprotein9. Alpha antitrypsin

ALBUMIN•Synthesized exclusively by liver•Its half life is 18-20 days •Due to its slow turn over – not a good indicator of acute or mild hepatic dysfunction• In hepatitis - <3g/dl of albumin – possibility of chronic liver disease•Non hepatic causes of Hypoalbuminemia - • Protein losing enteropathy• Nephrotic syndrome

PREALBUMIN /TRANSTHYRETIN• Levels fall in liver disease• Half life – 2 days • Sensitive indicator of any changes affecting its synthesis

and catabolism• PAB is a negative acute phase reactant• Particularly useful in drug-induced hepatotoxicity

• Normal plasma levels - 0.2-0.4g/L• Acute phase protein• Decreased in multiple conditions –1. Wilson’s disease2. Menkes disease3. Aceruloplasminemia4. Copper deficiency

CERULOPLASMIN

• Increased in –1. Copper toxicity2. Pregnancy3. OCPs

PROCOLLAGEN III PEPTIDE• Cleavage product of the type III procollagen

molecule• Radioimmunoassay• Elevated Conc. Of PIIIP- the transformation of

viable hepatic tissue into connective tissue/fibrosis

• AFP is a gp and MW – 70,000 daltons • Normally present in fetus • Liver, yolk sac and small intestine • AFP- ELISA

HCCNon seminomatous testicular cancer Ataxia telangiectasiaHereditary tyrosinemiaNeonatal hyperbilirubinemiaChronic active hepatitis

α- FETO PROTEIN

COAGULATION FACTORS •With the exception of F-VIII , all other factors are synthesized in liver•Half life ranges from 6hrs for F-VII to 5 days for fibrinogen• So their measurement is the single best measure of hepatic synthetic function• Tests – Serum prothrombin time •Marked increase in PT >5secs above the control and not corrected by Vit K administration – is a poor prognostic sign in acute viral hepatitis and other acute and chronic liver disease

Prothrombin is synthesized by liver Half life – 6 hrs so it indicate – present function of liver PT :blood test, time taken by blood to clot Normal value : 10 to 15 sec. PT is Prolonged - liver losses 80% of reserve capacity Commonly PT is used for detecting liver coagulopathies Note : Vit K deficiency Prolongs PT time But In case of LIVER diseases : PT remains prolonged even

after parenteral administration of Vit. K

PROTHROMBIN TIME

LIMITATIONS Lack sensitivity: The LFT may be normal in certain disesliver

disease like cirrhosis, non cirrhotic portal fibrosis ,cogenital hepatic fibrosis

Lack specificity: They lack specificity and are not specific for any particular disease. Serum albumin may be decreased in chronic disease and also in nephrotic syndrome. Amino-transferase may be raised in cardiac diseases and hepatic diseases.Except for serum bile acids the LFT are not specific for liver diseasesThus, we see that LFT have certain advantages as well as limitation at the same time

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