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Liver function test  Part 1 Liver function test  Part 1

Liver function test Part 1 - PowerPoint Presentation

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Liver function test Part 1 - PPT Presentation

Liver enzymeALTASTALPGGT Liver is the largest Organ of the body weighing about 15 Kg Liver is called kitchen of our body Major Metabolic Functions of the Liver Synthetic Function Plasma proteins albumin globulins cholesterol triglycerides and lipoproteins ID: 908443

ast liver alt alp liver ast alp alt mohammed laqqan serum activity glutamyl enzyme hepatitis group ggt plasma aminotransferase

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Slide1

Liver function test

Part 1

Liver enzyme(ALT-AST-ALP-GGT)

Slide2

Slide3

Liver is the largest Organ of the body weighing about 1.5 Kg.

Liver is called kitchen of our body.

Slide4

Major Metabolic Functions of the Liver

Synthetic Function

Plasma proteins (albumin, globulins), cholesterol, triglycerides and lipoproteins

Detoxification and excretion

Ammonia to urea (urea cycle), bilirubin, cholesterol, drug metabolites

Storage Function

Vitamins A, D, E, K and B

12

Production of bile salts

Helps in digestion

Slide5

Liver Function Tests (LFTs)

Noninvasive methods for screening of liver dysfunction

Help in identifying general types of disorder

Assess severity and allow prediction of outcome

Disease and treatment follow up

Slide6

Liver Function Tests (LFTs)

Broadly classified as:

Tests to detect hepatic injury:

Mild or severe; acute or chronic

Nature of liver injury (hepatocellular or cholestasis)

Tests to assess hepatic function

Slide7

Classification of LFTs

Group I: Markers of liver dysfunction

Serum bilirubin: total and conjugated

Urine: bile salts and

urobilinogen

Total protein, serum albumin and albumin/globulin ratio

Prothrombin

Time

Slide8

Classification of LFTs

Group II: Markers of hepatocellular injury

Alanine aminotransferase (ALT)

Aspartate aminotransferase (AST)

Slide9

Classification of LFTs

Group III: Markers of cholestasis

Alkaline phosphatase (ALP)

g

-

glutamyltransferase

(GGT)

Slide10

Liver Enzymes

Slide11

Aminotranferases

Aminotransferases or transaminases are a group of enzymes that catalyze the

interconversion

of amino acids and

ketoacids

(

oxoacids

) by transfer of amino group

The two aminotransferases of greatest clinical significance are:

Aspartate aminotransferase (AST), formerly termed glutamate oxaloacetate transaminase (GOT).

Alanine aminotransferase (ALT), formerly termed glutamate pyruvate transaminase (GPT

).

Pyridoxal

phosphate (P-5-P) is coenzyme

Slide12

Aspartate aminotransferase (AST)

AST involved in the transfer of an amino group between aspartate and

-

ketoacids

.

Mohammed Laqqan

Slide13

Clinical Significance

Aspartate aminotransferase (AST) is an enzyme found primarily in the

heart, liver

, and

muscle.

Additional AST is released into the circulation after injury or death of cells.

This test is one of several that are performed when there has been damage to the heart muscle, as in myocardial infarction, and in assessing liver damage.

Infants levels approximately twice the adult level, these decline to adult levels by approximately 6 months of age.

Mohammed Laqqan

Slide14

Specimen

Collection

Specimen:

Serum, heparin plasma or EDTA plasma

Hemolysis should be avoided because it can dramatically increase serum AST concentrations

(RBCs contain 15 X the AST activity in serum)

Mohammed Laqqan

Slide15

Assay for Enzyme activity

Measurement by

Karmen

method

A coupled reaction involving:

pyridoxal-5-phosphate (P-5-P)

and malate dehydrogenase (MDH)

at 37

o

C:

Decrease in absorbance at 340 nm is determined by continuous monitoring.

Aspartate +

-Ketoglutarate

Oxaloacetate + Glutamate

Oxaloacetate + NADH + H Malate + NAD

MD

AST

Mohammed Laqqan

Slide16

Normal range: 8 – 20

U/L

Post

AMI

Rises 6 – 8 hours

Peaks at 24 hours

Returns to normal by day 5

AST levels are highest in acute hepatocellular disorders "viral hepatitis, cirrhosis.

Slide17

Alanine Aminotransferase (ALT)

A

transferase

with enzymatic activity similar to AST

Converts alanine + α-

ketoglutarate

to pyruvate and glutamate

Mohammed Laqqan

Slide18

Clinical Significance

It is found in the kidneys, heart, and skeletal muscle tissue but primarily in liver tissue.

The test is used mainly in the diagnosis of liver disease and to monitor the effects of hepatotoxic drugs.

Often higher than AST with liver damage and tend to remain elevated longer

(

More liver-specific than

AST)

Remains normal in AMI

Mohammed Laqqan

Slide19

Specimen Collection

Specimen:

Serum, heparin plasma or EDTA plasma

Hemolysis should be avoided because it can increase serum ALT concentrations

(ALT in RBCs is roughly 5 X that of serum)

Mohammed Laqqan

Slide20

Assay for enzyme activity

The most common method in use today for measurement of ALT activity utilizes a coupled enzymatic procedure for monitoring disappearance of NADH.

In this approach lactate dehydrogenase (LDH) and its required cofactors are added and catalyze the conversion of pyruvate to lactate

This causes simultaneous oxidation of reduced

nicotinamide

adenine dinucleotide (NADH).

The disappearance of NADH is followed

spectrophotometrically

(at 340 nm).

Alanine +

-Ketoglutarate

Pyruvate + Glutamate

Pyruvate + NADH + H Lactate + NAD

LD

ALT

Slide21

Normal range (U/L):

Male

: 13-35

Female:

10-30

High serum levels in acute hepatitis (300-1000U/L)

Moderate elevation in alcoholic hepatitis (100-300U/L

)

Minor elevation in cirrhosis, hepatitis C and non-alcoholic

steatohepatitis

(NASH) (50-100U/L)

Slide22

Levels of AST & ALT

AST is assessed along ALT in monitoring liver damage.

These two values normally exist in an approximately 1:1 ratio.

As a rough guide:

AST>ALT in:

alcoholic hepatitis and cirrhosis,

metastatic cancer of the liver

non-biliary cirrhosis,

while ALT>AST in:

viral and drug hepatitis,

chronic hepatitis C

and hepatic obstruction.

Mohammed Laqqan

Slide23

Alkaline Phosphatase (ALP)

Phosphatases transfer a phosphate moiety from one group to a second, forming an alcohol and a second phosphate compound.

The optimal reaction pH for ALP is between 9 and 10 and varies with the buffer and substrate.

ALP requires Mg

2+

as an activator

Mohammed Laqqan

Slide24

Isoenzymes

ALP exists as a number of

isoenzymes

Major are those found in Liver, bone, placenta, and then intestinal fraction

Electrophoresis for

isoenzyme

analysis

Liver

isoenzyme

(fastest)

Bone

isoenzyme

Placental

isoenzyme

Intestinal

isoenzyme

(slowest)

Immunochemical methods now available

Mohammed Laqqan

Slide25

Clinical Significance

Alkaline phosphatase (ALP) is an enzyme found in the liver, bone, placenta, intestine, and kidneys

Primarily in the cells lining the biliary tract and in the osteoblasts involved in the formation of new bone.

ALP is normally excreted from the liver in the bile.

Increased ALP levels are found most commonly during:

periods of bone growth (as in children),

in various types of liver disease,

and in biliary obstruction.

Serum ALP activity primarily reflects changes in bone and liver function, even though higher ALP activities can be found in other organs.

Mohammed Laqqan

Slide26

Specimen Collection

Blood should be drawn after a fast of at least 8 hours.

Serum or heparinized plasma.

Slight hemolysis is tolerable, but gross hemolysis should be avoided.

These increases may be caused by:

the release of ALP from complexes with lipoproteins,

It is best to analyze ALP specimens the same day they are drawn.

ALP is inhibited by metal-

complexing

anticoagulants; EDTA, oxalate, and citrate inhibit the enzyme by

complexing

Mg

2+

and should not be used.

Mohammed Laqqan

Slide27

Assay for Enzyme activity

almost all assays for ALP employ p-

nitrophenyl

phosphate as the substrate.

Bowers and Combs method based on absorption of p-

nitrophenol

at 405 nm

At an alkaline pH,

p-

nitrophenyl

phosphate is colorless;

the product p-

nitrophenol

is intensely yellow

Slide28

Normal range:

40 – 125 U/L

Slide29

γ-

Glutamyltransferase

(GGT)

Transfers γ-

glutamyl

residue from γ-

glutamyl

peptides (usually glutathione) to amino acids, H

2

O and other small peptides

glutathione serves as the

γ

-

glutamyl

donor

Glutathione + Amino Acid

glutamyl

-peptide + L-

cysteinylglycine

High concentrations in liver tissue

Also in pancreas and kidney

GGT

Slide30

Diagnostic Significance

Increased plasma GGT is associated with

Hepatobiliary

disease

Highest seen in biliary obstruction

Alcoholic cirrhosis

Used with ALP to differentiate between liver and bone diseases

Slide31

Assay for enzyme activity

γ-

glutamyl

residue of γ

glutamyl

-p-

nitroanilide

is transferred to

glycylglycine

, releasing p-

nitroaniline

L-γ-

glutamyl

-p-

nitroanilide

+

glycylglycine

p-

nitroaniline

+ y-

glutamyl

glycylglycine

The rate of liberation of p-

nitroaniline

is directly related to the GGT activity in the sample and is quantitated by measuring the increase in absorbance at 405 nm.

GGT

Reference Range:

male, 6-45 U/L (37°C); female, 5-30 U/L (37°C)