A blood test called a direct antiglobulin test (DAT), also known as the Coombs test, is used to confirm Autoimmune Hemolytic Anemia (AIHA).
Understanding the DAT
The DAT helps identify antibodies that are attached to red blood cells (RBCs). These antibodies can be present in AIHA, where the immune system mistakenly attacks the body's own RBCs.
How the Test Works
- Blood Sample: A blood sample is taken from the patient.
- Red Blood Cell Isolation: The RBCs are separated from the rest of the blood.
- Antiglobulin Reagent: A special reagent containing antibodies against human immunoglobulins (like IgG and IgM) is added to the isolated RBCs.
- Agglutination: If antibodies are attached to the RBCs, they will bind to the antiglobulin reagent, causing the RBCs to clump together (agglutinate).
- Positive Result: Agglutination indicates a positive DAT result, suggesting the presence of antibodies against RBCs.
Interpreting the Results
A positive DAT result does not automatically confirm AIHA. Other conditions can also cause a positive result. The doctor will consider other symptoms, medical history, and other test results to make a diagnosis.
Other Tests
In addition to the DAT, other tests may be performed to help diagnose AIHA, including:
- Complete Blood Count (CBC): Measures the number of RBCs, white blood cells, and platelets in the blood.
- Reticulocyte Count: Measures the number of immature RBCs in the blood.
- Peripheral Blood Smear: Examines the shape and appearance of RBCs under a microscope.
