What is the Coombs test, and how is it used? (2025)

Answered on:2025-05-18

The Coombs test, also known as the antiglobulin test, is a laboratory procedure used to detect antibodies that attack red blood cells. This test is essential for diagnosing various blood conditions, particularly those related to immune reactions.

1. **Purpose**:

- The Coombs test is primarily used to identify antibodies against red blood cells. These antibodies can be either naturally occurring or induced by external factors like diseases or medications.

- It can be used before procedures such as blood transfusions to ensure compatibility or to diagnose conditions like hemolytic anemia, autoimmune diseases, or reactions to certain medications.

2. **Types**:

- **Direct Coombs Test**: This test detects antibodies that are already attached to the surface of red blood cells. It is commonly used to investigate conditions like autoimmune hemolytic anemia, where the immune system attacks its own red blood cells [1], [3].

- **Indirect Coombs Test**: This test detects free antibodies in the blood serum, which have not yet attached to red blood cells. It's often used in prenatal testing to check for Rh incompatibility in pregnancies [5], [9].

3. **Procedure**:

- A blood sample is taken from the patient, and the serum is mixed with red blood cells. In the case of the direct test, if antibodies are present on the red blood cells, they will react with a reagent that causes visible agglutination (clumping). In the indirect test, the serum is tested for free antibodies before mixing with red blood cells [2], [7].

4. **Clinical Significance**:

- A positive result indicates the presence of antibodies against red blood cells, which may suggest immune-related conditions such as hemolytic anemia, Rh incompatibility during pregnancy, or drug-induced hemolysis [6].

In summary, the Coombs test is a valuable diagnostic tool used to detect antibodies that can attack red blood cells, helping to diagnose a variety of immune-mediated blood disorders.

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