You are currently viewing 38 Difference Between Complement Fixation Test and Hemagglutination Test

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.



Complement Fixation Test

Hemagglutination Test


Type of Test





Detect antibodies or antigens

Detect antibodies or antigens



Measures the consumption of complement

Agglutination of red blood cells


Components Required

Serum, complement, antigen, and antibodies

Antigen-coated red blood cells



High sensitivity

Variable sensitivity



High specificity

Variable specificity


Sensitivity to Antibodies

Detects both IgG and IgM antibodies

Mainly detects IgM antibodies


Antigen Detection

Detects soluble antigens

Detects particulate antigens


Incubation Time

Requires longer incubation time

Typically shorter incubation time


Result Measurement

Based on complement fixation

Based on agglutination


Quantitative Measurement

Can be quantitatively measured

Usually qualitative, titration possible


Common Uses

Diagnose viral and bacterial infections

Blood typing, serological diagnosis



Less prone to cross-reactions

More prone to cross-reactions



Requires specialized equipment

Basic laboratory equipment


Risk of Hemolysis

Lower risk of hemolysis

Higher risk of hemolysis


Handling of Blood Samples

Serum or plasma needed

Whole blood or serum samples used


Result Interpretation

Positive if no complement fixation

Positive if agglutination observed


Test Complexity

More complex to perform

Simpler and quicker to perform



Generally more expensive

Generally less expensive


Sensitivity to Antigen Size

Suitable for small antigens

Suitable for larger antigens


Viral Infections

Useful for diagnosing some viral infections

Less commonly used for viral infections


Bacterial Infections

Useful for diagnosing some bacterial infections

Less commonly used for bacterial infections



Requires a control sample for validation

Control sample less critical



Used in syphilis, brucellosis diagnosis

Used in blood typing, influenza diagnosis


Hemagglutination Type

Not associated with hemagglutination

Relies on hemagglutination reaction


Hemagglutination Inhibition

Does not involve hemagglutination

Utilizes hemagglutination inhibition


Interpretation of Results

Based on the absence/presence of fixation

Based on the presence/absence of agglutination


Antigen Sources

Various antigen sources can be used

Usually, specific RBC antigens are used


Diagnostic Sensitivity

May have higher diagnostic sensitivity

May have lower diagnostic sensitivity


Risk of False Positives

Lower risk of false positives

Higher risk of false positives


Risk of False Negatives

Lower risk of false negatives

Higher risk of false negatives


Test Duration

Longer test duration

Shorter test duration



Less amenable to automation

More amenable to automation


Interpretation of Titers

Titers are not typically used

Titers may be used for quantitative analysis


Serum Handling

Serum must be heat-inactivated

Serum may not require heat-inactivation


Research vs. Clinical Use

More commonly used in research settings

More commonly used in clinical settings



May not be widely available in all labs

Generally available in most labs


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.

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