Omar Adwan Explains Antibody Detection with the HI Test
Omar Adwan, Medical Laboratory Technologist of Modawah lab center, shared a post on LinkedIn:
“Hemagglutination Inhibition (HI) Test:
1. Objective
To identify and measure antibodies that inhibit the ability of viruses to agglutinate red blood cells (RBCs)
2. Principle
Certain viruses (like Influenza) have surface proteins (hemagglutinins) that cause RBCs to clump together (hemagglutination).
If a patient’s serum contains specific antibodies, they will bind to the virus and block hemagglutination.
Thus, no agglutination = positive inhibition = antibodies present.
3. Materials
Patient serum sample
Viral antigen (e.g., Influenza virus)
Red blood cells (usually chicken, guinea pig, or human O-type)
Microtiter plates (V-bottom or U-bottom)
Phosphate buffered saline (PBS)
Micropipettes
4. Procedure
- Heat inactivate the patient serum (to remove non-specific inhibitors).
- Prepare serial dilutions of serum in microtiter plate wells.
- Add a constant amount of virus antigen to each well.
- Add a standardized suspension of RBCs.
- Incubate and observe results.
5. Results
Positive (Inhibition): A clear button of RBCs at the bottom of the well (no agglutination). Indicates presence of antibodies.
Negative (No Inhibition): RBCs form a diffuse lattice across the well (agglutination occurs). No antibodies present.
The HI titer is the highest serum dilution that completely inhibits hemagglutination.
6. Uses
Diagnosis of viral infections (e.g., Influenza, Measles, Mumps, Rubella).
Measurement of antibody titers after vaccination.
Surveillance of circulating viral strains.
7. Conclusion
The HI test is a simple, sensitive, and widely used method for detecting virus-specific antibodies and plays a key role in vaccine development and viral epidemiology.”

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