Tests to assess liver function :

The liver function tests (LFT) are the biochemical investigations to assess the capacity of the liver to carry out any of the functions it performs. LFT will help to detect the abnormalities and the extent of liver damage.

Two important facts should be borne in mind while carrying out LFT.

• Liver is a large-size factory of safety. Therefore, it can perform many of its functions almost normally, despite the damage.

• Selection of the right test is important in LFT. This is due to the fact that since liver participates in several functions, the function that is measured in LFT may not be the one that is adversely affected. The major liver function tests may be classified based on :

a. Excretory function - Measurement of bile pigments, bile salts, bromosulphthalein.

b. Serum enzymes derived from liver - Determination of transaminases, alkaline phosphatase, 5'-nucleotidase, y-glutamyl-transpeptidase.

c. Metabolic capacity - Galactose tolerance, antipyrine clearance.

d. Synthetic functions - Prothrombin time, serum albumin.

e. Detoxification - Hippuric acid synthesis.

 

The choice of biochemical tests to measure liver functions mostly depends on the purpose of the investigation.

The clinical history of the subject is often a guiding factor in this regard.

A single test in isolation may have a little diagnostic value.

Frequently, a combination of laboratory investigations are employed in LFT.

These include serum bilirubin (conjugated and unconjugated), alanine transaminase, aspartate transaminase, alkaline phosphatase, y-glutamyl transpeptidase and proteins (albumin, globulins). The most commonly used tests include the estimation of levels of serum enzymes.