Complement Fixation test is: September 2005

Complement Fixation test is:
September 2005
b) Coombs test
c) Wassermann reaction
Correct Answer - C
Ans. C: Wassermann reaction
The complement fixation test (CFT) was extensively used in syphilis
serology after being introduced by Wasserman in 1906. However,
there is now a trend to replace the CFT with the simple flocculation
Although CFT is considered to be a relatively simple test, it is a very
exacting procedure because 5 variables are involved. In essence the
test consists of two antigen-antibody reactions, one of which is the
indicator system.
The first reaction, between a known virus antigen and a specific
antibody takes place in the presence of a predetermined amount of
complement. The complement is removed or “fixed” by the antigen-
antibody complex.
The second antigen-antibody reaction consists of reacting sheep
RBC with haemolysin. When this indicator system is added to the
reactants, the sensitized RBCs will only lyse in the presence of free
complement. The antigens used for CFT tend to be group antigens
rather than type-specific antigens. In order for the CFT to be set up
correctly, the optimal concentration of haemolytic serum,
complement, and antigen should be determined by titration.
The Wassermann test is no longer in use.