Lab # 2 Liver Function Tests (LFTs) - PowerPoint Presentation

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Lab # 2Liver Function Tests (LFTs) ALT&AST

T.A. Bahiya M. Osrah

Liver FunctionsThe liver is in the upper right part of the abdomen. The functions of the liver include:

1-storing glycogen (fuel for the body) which is made from sugars. 2-process the body nutrients

3-Produce proteins that are essential for blood to clot (clotting factors).

4-processing many medicines which you may take.

5- helping to remove poisons and toxins from the body.

6- Manufactures bile to help in fat digestion.

Liver function tests-LFTs are group of clinical biochemistry laboratory blood assays designed to give information about the state of a patient’s liver.

-As the liver performs it's various functions it makes a number of chemicals that pass into the bloodstream and bile. Various liver disorders alter the blood level of these chemicals. Some of these chemicals can be measured in a blood sample. Some tests that are commonly done on a blood sample are called 'LFTs' (liver function tests).

Liver function tests can be classified as: a. Tests of excretion by the liver. b. Evaluation of synthesis in liver. c. Evaluation of enzyme activity.

 Liver function tests are most often employed to determine:

i. The presence of liver disease.

ii. The type of liver disease.

iii. The extent and progression of liver disease.

Liver function tests

When are these tests ordered?Liver disorder symptoms:Weakness, FatigueJaundice (yellow skin, increase billirubin

)Dark urine, light colored stoolNauseaVomiting

Diarrhea

Hepatitis Virus

Excessive alcohol intake

Liver function tests

Liver function tests (LFT)

Alanine Aminotransferase (ALT)=SGPT:

ALT is glutamic pyruvate transaminase enzyme which is mainly found in

liver

cells but it also found in smaller amounts in heart and muscles

.

The enzymatic reaction:

Alanine + α-

Ketoglutarate

ALT Glutamate + Pyruvate

The

ALT level in blood is normally low and it abnormality increased in conditions where cells of the liver have been inflamed or undergone cell death.

As the cells are damaged, the ALT leaks into the bloodstream leading to a rise in the serum levels.

1) Alanine Aminotransferase (ALT)=SGPT:

ALT is the most useful test for detecting liver damage.

Very

high values of ALT(more than 10 times of the normal

value) due

to acute hepatitis (Virus infection)

Moderate level (4 times) due to the bile duct obstruction

Factors that raise the ALT levels:

Drugs

Some medical shots or injections into the muscles may increase ALT levels

1) Alanine Aminotransferase (ALT)=SGPT

Why the test is ordered:

to

the evaluation of hepatic disorders (liver disease).

ALT

test is often ordered in conjunction with

another test called AST

ALT values are often compared to other tests, such as ALP, total protein, and bilirubin (will be discussed later) in order to distinguish between different causes of liver damage.

ALT is the most specific for liver disease diagnosis than the other tests.

Used Sample

:

Blood

2) Aspartate Aminotransferase (AST)=SGOT

General Information:It is a glutamic oxaloacetic transaminase enzyme that found mostly in

liver cells

and

heart

(cardiac muscles) but in smaller amounts in kidney and skeletal muscles.

AST level is normally low in blood but when liver and muscles are injured, it got released into the blood stream.

Aspartate + α-

ketoglutarate

AST oxaloacetate + glutamate

2) Aspartate Aminotransferase (AST)=SGOT

Why the test is performed:

This enzyme also reflects damage to the hepatic cell. It is less specific for liver disease. It may be elevated and other conditions such as a myocardial infarct (heart attack).

- AST test is often ordered in conjunction with ALT

- Although AST is not a specific for liver as the ALT, ratios between ALT and AST (AST/ALT) are useful to physicians to distinguish between the different causes of liver disease and also in assessing the etiology of liver enzyme abnormalities.

Used

Sample:

Blood

3) Alkaline Phosphatase (ALP)

General Information:

Alkaline

phosphatase is an enzyme, it is mainly found in

liver

and

bone

It found

in many tissues, such as liver (associated with the biliary tract), bone, kidney, intestine, and placenta

.

Why the test is ordered:If the alkaline phosphatase is elevated, it could be due to two reasons, either a liver disease or bone disorder.

One of the more common methods to assess the etiology of the elevated alkaline phosphatase is to determine whether the GGT is elevated or whether other function tests are abnormal (such as bilirubin) Alkaline phosphatase may be elevated in primary biliary cirrhosis, alcoholic hepatitis.

3) Alkaline Phosphatase (ALP

)

Note:Both GGT and ALP are elevated in the case of liver disease while ALP is the only marker which got elevated in bone disorder.So, the suggested next step to distinguish the causes of the elevated levels of ALP is to perform GGT test.

Used Sample:Blood

3) Alkaline Phosphatase (ALP

)

4) Gamma Glutamic Transpeptidase (GGT

)

General

Information:

GGT is an enzyme found in many organs, such as kidney, liver, spleen and pancreas; however, the main source of GGT in the blood is the liver

.

it is not very specific

to the liver or bile ducts

It is used often times to confirm that the alkaline phosphatase is of the hepatic etiology.

Elevated levels of GGT are due to:

Liver disease

Heart disease

Alcohol

consumption

Medications commonly cause GGT to be elevated

Why the test is ordered:

It is mainly to determine if the elevated serum level of ALP was because of Liver disease or bone disorder especially in the cases of high ALP level and unchanged AST or ALT.

GGT

is not helpful test in distinguishing between the different causes of liver damage.

Used Sample:

Blood

8

h fasting is recommended because GGT drops after eating.

4) Gamma

Glutamic

Transpeptidase

(GGT

)

LFTsOther tests include:Blood clotting tests

Total proteins. 

Immunological

studies

Prothrombin

time (PT)

Liver

biopsy, ultrasound scan, other types of scan,

etc

, may be needed to clarify the cause of a liver disorder, and/or to monitor its progress.

Lab practice:AST

-Collect blood and prepare serum in an appropriate tube.

-Measure ALT and AST levels.

-Compare the results to the normal values.

Assay for Enzyme Activity:

•

L-aspartate

+

α

-

oxaloglutarate

AST L-glutamate + oxaloacetate

Oxaloacetate +

NADH

+H

MDH

L-malate + NAD+

•

The rate of decrease in conc. of NADH, measured

photometrical,

is proportional to the

activity

of

AST

present in the sample.

CalculationX= A 2min - A 1min

Y= A 1min - A 30s

Catalytic concentration=

(X + Y / 2) x factor

1946

Reference Range: Normal: 6 – 37 U/L

Interfering Factors:

• Many drugs may cause falsely increased and decreased ALT levels.

• Therapeutic heparin increases ALT.

•

Hemolysed

blood increases ALT.