Back to: MICROBIOLOGY 100 LEVEL
Welcome to class!
It’s great to have you here again! You’ve been learning so much about how the immune system works, and today’s topic will help you understand how doctors and scientists check for infections and immune responses in the lab. We’re talking about basic serological tests—simple tests that use blood serum to detect antibodies or antigens in the body. Don’t worry, we’ll break everything down in a clear and relatable way you’ll easily understand.
Basic Serological Tests
Serological tests are laboratory tools used to detect antibodies or antigens in a person’s blood. These tests help diagnose infections, determine immunity, and even guide treatment. They’re called “serological” because they are performed on serum, the clear liquid part of the blood that remains after the red and white blood cells are removed.
Let’s go over a few common and important serological tests.
1. Agglutination Tests
These tests work by mixing a patient’s serum with particles that contain antigens or antibodies. If the matching antibody or antigen is present, clumping (agglutination) will occur.
Used for blood typing, detecting bacteria, and identifying antibodies in the blood.
Example: When preparing for a blood transfusion, agglutination tests help ensure the donor and recipient blood types are compatible.
2. Precipitation Tests
In these tests, a soluble antigen and antibody are mixed. If they are a match, they form a precipitate—a solid that can be seen in the solution.
It’s a way to detect and measure specific antibodies.
Example: Precipitation tests can help identify infections like syphilis.
3. ELISA (Enzyme-Linked Immunosorbent Assay)
This is one of the most widely used serological tests. ELISA detects the presence and amount of either antibodies or antigens in the serum using enzymes that produce a colour change.
It is very sensitive and specific.
Used for: Detecting HIV, hepatitis, and COVID-19 antibodies.
Example: During the COVID-19 pandemic, ELISA was used to check if someone had been exposed to the virus by testing for antibodies.
4. Western Blot
Often used to confirm the results of an ELISA test. It separates proteins based on size and checks for the presence of specific antibodies.
It is more accurate and specific, but more complex.
Example: Used in HIV diagnosis after an ELISA screening.
5. Rapid Diagnostic Tests (RDTs)
These are simple, point-of-care tests that give results quickly—often in under 30 minutes.
Used widely for diseases like malaria, HIV, and COVID-19.
They often work on the principle of immunochromatography, where coloured lines appear if antibodies or antigens are present.
Example: The COVID-19 self-test kit is a rapid serological test.
Summary
- Serological tests detect antibodies or antigens in blood serum.
- Agglutination tests show clumping and are used in blood typing and infection detection.
- Precipitation tests form solid complexes when antigens and antibodies bind.
- ELISA is a colour-based test used to detect a wide range of infections like HIV and COVID-19.
- Western blot confirms ELISA results and is highly specific.
- Rapid diagnostic tests (RDTs) provide fast, simple results using a drop of blood or saliva.
Evaluation
- What is a serological test, and what part of the blood does it use?
- Name two diseases that can be diagnosed using ELISA.
- What is the main difference between an agglutination test and a precipitation test?
- Which serological test gives quick results and is used at the point of care?
By learning about these tests, you’re one step closer to understanding how laboratories help diagnose diseases and support good health. Keep going strong—Afrilearn is cheering you on as you build a future full of knowledge and purpose. See you next class!