Liver Test

What causes the enzymes to be raised in a Liver Function Test? 

 

The reason why all or some of these enzymes become elevated in cases of liver disease is that they are normally contained inside the liver cells (hepatocytes). They only leak into the blood stream when the liver cells are damaged. Thus measuring liver enzymes is only able to detect liver damage and does not measure liver function in a sensitive way.

Other tests can be done to check the ability of the liver to manufacture its vital proteins. These are tests for the proteins albumin, prothrombin, and various globulins and they show characteristic abnormalities in those whose liver function is abnormal. 

 

Tests for Liver Function:- 

 

What is a Liver Function Test?

 
Blood samples are analyzed for levels of specific enzymes in the blood stream – there are generally 5 – 6 specific things that are checked. Collectively these tests are called a “Liver Function Test” or LFT. These enzymes are what are referred to as ‘markers’ of disease and dysfunction. 

 

How reliable is this test?

 
The name “Liver Function Test” is actually quite misleading as this test does not actually measure the ‘function’ of the liver. It is more a marker of the status of the integrity of the liver cell membranes. 

 

Most of the standard or routine blood tests that your doctor will order to check “liver function” are in reality only able to detect liver disease. These tests are not sensitive enough to accurately reflect liver function.

 

It is possible to still have liver disease even though blood tests are normal. Therefore the LFT alone is not capable of making a proper diagnosis of many liver conditions. 

 

Different diseases of the liver will cause differing types of damage and affect liver function tests accordingly. It can be possible to give an idea of which disease may be suspected from a liver function test, but these tests are not the absolute way of diagnosing liver disease. They are helpful, but not the whole story. They are also useful for monitoring someone with liver disease, but are not always accurate.

 

As the LFT is really only showing the level of enzymes present in the blood stream it is only showing that some damaging is occurring but does not give an indication of the extent. 

 

 

A Typical Liver Function Test

Liver function	Normal value(U /L)
Alk . Phos.	30 - 120
GGT (Gamma GT )	5   -  35
LD Lactate Dehydrogenase	100 - 225
AST (Aspartate amino   transferase)	5    - 45
ALT (Alanineaminotransferase)	5    - 45
Albumin (g/L)	38   - 55
Prothrombin Time(seconds)	11  -  13.5
Total Bilirubin (mg / dl)	0.1  - 1.0

 

 Each laboratory will provide a “reference range” or ‘normal values’ this is the average reading that is deemed a ‘normal’ reading for the majority of the population. This will assist the Doctor in determining if the patient's results are abnormal. 

 

The normal values for liver function tests will vary between men and women, at different times of the day and will change as you get older. Different laboratories may have slightly differing reference ranges.