Complement fixation test.ppt

complement fixation test is used to identify pathogenic antigen or antibody in serum sample.

1. Complement Fixation Test
to detect the presence of specific antibodies in the sample serum.

2. Complement Fixation ?
Complement: a Biologically labile serum factor
that causes the immune cytolysis i.e. lysis of
antibody coated cells.
https://www.onlinebiologynotes.com/wp-content/uploads/2018/03/CFT-
positive.jpg

3. Principle
1. Complement is irreversibly bound (fixed) by certain classes of
antibody-antigen complexes.
The degree of fixation is governed by the relative concentration of
antibody or antigen
2. The lysis of RBC that have been sensibilized with RBC’s antibody is
dependent upon the presence of unbound complement.

4. https://laboratoryinfo.com/wp
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content/uploads/2015/03/complement
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fixation
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test.jpg
Method & Mechanism
1. A known antigen (cardiolipin/Viral Ag/sheep RBC) is
mixed with inactivated patient’s serum
2. Add a measured amount of complement (Guineapig
serum) in the test system
3. The test system is incubated at 37°C for about 1 hour.
4. After 1 hour an indicator system (sensitized RBC) is
added to the test system and again incubated at 37°C for
30 minutes
5. If Ag and Ab matches, they form Ag-Ab complex and
utilizes complement.
6. Observe the result

5. https://www.biotrend.com/en/upload/cft-tjkrma.gif
Cytolysis / HemolysisResults
Hemolysis ObservedNegative test
No Hemolysis Positive test
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+ +
Observation & Results
1. If hemolysis is observed: it indicates the absence of specific antibody in patient
serum, so that complement has not been used which lysed the sensitized RBC
giving hemolysis.
2. If no hemolysis is observed: it indicates that the patient serum contains antibody
which reacts with Ag to form Ag-Ab complex and then fix complement.
so that no complement is available to hemolyse sensitized RBC.

6. Applications
CFT is used to detect and quantify antibody that
does not agglutinate or precipitate with its
antigen.
CFT can detect antibody at level less than 1
microgram per milliliter.
CFT is also used to detect antigen
CFT is Economical
CFT can be used to screen large numbers of
viral or bacterial infection.
Limitations
Non specific
Time consuming
Labour intense

7. Ref:
1)https://en.wikipedia.org/wiki/Complement_fixation_test
2)https://laboratoryinfo.com/complement-fixation-test/
3)https://www.onlinebiologynotes.com/complement-fixation-test-principle-procedure-result-interpretation-applications-and-
limitations/
4)https://www.biotrend.com/en/read/serological-tests-in-mycology-1190/complement-fixation-test-cft-2094.html
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