38 Difference Between Complement Fixation Test and Hemagglutination Test

Both the complement fixation test (CFT) and the hemagglutination test are immunological tests used to find out whether a biological sample contains particular antibodies or antigens. These assays are frequently used in research, clinical diagnosis, and immunology.

A serological technique called the complement fixation test detects the presence of particular antibodies in a patient’s serum sample. This test is based on how antibodies and complement proteins interact to protect the immune system from external invaders like bacteria and viruses.

The CFT operates as follows:

The test includes mixing various dilutions of the patient’s serum with a predetermined quantity of an antigen (such as a virus or bacterial component) in a succession of tubes or wells.
Specific antibodies against the antigen will attach to the antigen molecules if the patient’s serum contains those antibodies. The complement cascade can then be activated as a result of complement proteins binding to the antigen-antibody complexes.
Hemoglobin is released when indicator cells—typically sheep or rabbit red blood cells—are lysed (destroyed) in the complement cascade’s last stage. The color or turbidity will change, making this lysis visible.
The complement proteins will “fix” to the antigen-antibody complexes if antibodies are present in the blood sample. As a result, the indicator cells won’t be damaged and the complement cascade won’t be triggered.

Hemagglutination and complement fixation tests are crucial immunological methods for identifying particular immune responses and comprehending the interactions between antigens and antibodies.

Hemagglutination test results:

Red blood cells are combined with antigens (such as bacterial or viral particles). They will attach to both the antigen and the red blood cells if particular antibodies directed against these antigens are found in the test sample. Red blood cells agglutinate as a result, generating distinct clumps.
Depending on the quantity of antibodies and the potency of the antigen-antibody interaction, the degree of agglutination can change. The test can be used statistically to calculate the titer of the antibodies or qualitatively to assess whether or not a particular antibody is present.

Hemagglutination and complement fixation tests are crucial immunological methods for identifying particular immune responses and comprehending the interactions between antigens and antibodies.

S.No.	Aspect	Complement Fixation Test	Hemagglutination Test
1	Type of Test	Serological	Serological
2	Purpose	Detect antibodies or antigens	Detect antibodies or antigens
3	Principle	Measures the consumption of complement	Agglutination of red blood cells
4	Components Required	Serum, complement, antigen, and antibodies	Antigen-coated red blood cells
5	Sensitivity	High sensitivity	Variable sensitivity
6	Specificity	High specificity	Variable specificity
7	Sensitivity to Antibodies	Detects both IgG and IgM antibodies	Mainly detects IgM antibodies
8	Antigen Detection	Detects soluble antigens	Detects particulate antigens
9	Incubation Time	Requires longer incubation time	Typically shorter incubation time
10	Result Measurement	Based on complement fixation	Based on agglutination
11	Quantitative Measurement	Can be quantitatively measured	Usually qualitative, titration possible
12	Common Uses	Diagnose viral and bacterial infections	Blood typing, serological diagnosis
13	Cross-Reactions	Less prone to cross-reactions	More prone to cross-reactions
14	Equipment	Requires specialized equipment	Basic laboratory equipment
15	Risk of Hemolysis	Lower risk of hemolysis	Higher risk of hemolysis
16	Handling of Blood Samples	Serum or plasma needed	Whole blood or serum samples used
17	Result Interpretation	Positive if no complement fixation	Positive if agglutination observed
18	Test Complexity	More complex to perform	Simpler and quicker to perform
19	Cost	Generally more expensive	Generally less expensive
20	Sensitivity to Antigen Size	Suitable for small antigens	Suitable for larger antigens
21	Viral Infections	Useful for diagnosing some viral infections	Less commonly used for viral infections
22	Bacterial Infections	Useful for diagnosing some bacterial infections	Less commonly used for bacterial infections
23	Validation	Requires a control sample for validation	Control sample less critical
24	Examples	Used in syphilis, brucellosis diagnosis	Used in blood typing, influenza diagnosis
25	Hemagglutination Type	Not associated with hemagglutination	Relies on hemagglutination reaction
26	Hemagglutination Inhibition	Does not involve hemagglutination	Utilizes hemagglutination inhibition
27	Interpretation of Results	Based on the absence/presence of fixation	Based on the presence/absence of agglutination
28	Antigen Sources	Various antigen sources can be used	Usually, specific RBC antigens are used
29	Diagnostic Sensitivity	May have higher diagnostic sensitivity	May have lower diagnostic sensitivity
30	Risk of False Positives	Lower risk of false positives	Higher risk of false positives
31	Risk of False Negatives	Lower risk of false negatives	Higher risk of false negatives
32	Test Duration	Longer test duration	Shorter test duration
33	Automation	Less amenable to automation	More amenable to automation
34	Interpretation of Titers	Titers are not typically used	Titers may be used for quantitative analysis
35	Serum Handling	Serum must be heat-inactivated	Serum may not require heat-inactivation
36	Research vs. Clinical Use	More commonly used in research settings	More commonly used in clinical settings
37	Availability	May not be widely available in all labs	Generally available in most labs
38	Historical Significance	Developed earlier in the history of serology	Developed later in the history of serology

Frequently Asked Questions (FAQs)

Q.1 What does the CFT intend to achieve?

Certain infectious disorders, particularly those brought on by viruses and bacteria that are challenging to grow, are diagnosed using the CFT. A person’s immunological response to vaccinations or earlier diseases is also ascertained using this method.

Q.2 What are the CFT's restrictions?

It is difficult and time-consuming to perform the CFT since live complement proteins are involved. Additionally, it is expensive and calls for knowledgeable staff and specialized equipment.

Q.3 How is the outcome of the hemagglutination test interpreted?

Positive outcomes demonstrate observable agglutination, which denotes the presence of particular antibodies or viruses. The titer, or the dilution at which agglutination takes place, can reveal details about the immunological response of the patient.

Q.4 Why is the hemagglutination test performed?

The Hemagglutination Test is mainly used to identify viral infections like influenza and certain viruses that cause respiratory or gastrointestinal diseases.

Q.5 What is the process of the hemagglutination test?

Red blood cells are combined with the patient’s serum for this test. These antibodies will bind to the virus if the serum has particular antibodies against the virus. As a result, the red blood cells that have been exposed to the virus clump together.