What is the Full Form of CFT? 

The full form of CFT is Complement Fixation Test. It is one of the most important traditional blood serum diagnostic procedures used to identify an antibody in a person’s serum samples based on whether or not fixation exists. CFT is mostly used to diagnose illnesses. It was invented by Wasserman in 1909. It was once widely utilised in syphilis serology.

How CFT Operates? 

• A complement is a protein contained in normal blood serum called globulin.
• It attaches to the immunological complex formed during the antigen-antibody response (Ag-Ab).
• The addition of the complement to the complex causes lysis of the cell in which the Ag-AB complex is formed.
• When a complement participates in antigen-antibody complexes, it is fixed or linked to the complex of antigen-antibody.
• While the complex is on bacteria, red blood cells, or other cells, the complement drives the lysis of the concerned cells.
• The terminal parts of the complement damage the cell membranes in the presence of a particular antibody that binds the supplement to the cell surface.
• Because the CFT uses erythrocytes as the target cell, complementary induced cell membrane damage can be measured as a rise in free haemoglobin.
• When specific antibodies are discovered in blood serum in response to an infectious agent, a complement is attached to the Ag-Ab group, preventing any residual complement from responding with antibodies belonging to erythrocytes and so preventing hemolysis.
• The absence of hemolysis thus suggested the presence of specific antibodies in the blood serum.
• If hemolysis occurs, the particular antibody is not detectable in the blood serum.

Advantages of CFT

Following are some of the advantages of the CFT test: 

• It can detect a large number of viral and bacterial Infections at the same time.
• It is a cost-effective assessment. 

Conclusion 

The CF test is widely used to screen for antibodies against a variety of potentially dangerous pathogens (especially viruses); for this purpose, a pool of 15-20 antigens can be utilised. The majority of antigens are readily available and reasonably priced. The test can be performed mostly with crude antigens (infected cell lysates). Because an excess of antibodies in high-titer sera may prevent the formation of complement-activating immune complexes (the “prozone’ effect”), test sera must be examined in at least two dilutions. The CF test cannot be used if the patient serum specimen is ‘anticomplementary,’ that is, it consumes complement from the test combination without contributing antigen.

Anti-complementarity is usually caused by the presence of pre-existing complement-activating components in the patient’s sera. These include immunological complexes and other immune aggregates, cryoglobulins, contaminating microbes, and bacterial products such as endotoxin. Acute sera from parvovirus B19 patients, for example, usually contain immune complexes that are anticomplementary.

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