What is the Difference Between Direct and Indirect Coombs Test?
🆚 Go to Comparative Table 🆚The Coombs test, also known as the antiglobulin test, is an immunology laboratory procedure used to detect the presence of antibodies against circulating red blood cells (RBCs). There are two types of Coombs tests: direct and indirect.
Direct Coombs Test:
- Checks the surface of red blood cells for antibodies by washing the blood sample and isolating red blood cells.
- Used to identify hemolytic anemia, a condition in which RBCs are prematurely destroyed.
- Positive result indicates the presence of antibodies attached to RBCs, but may not necessarily determine which antibodies or why they are present.
Indirect Coombs Test:
- Checks blood before a person undergoes a blood transfusion or during prenatal testing of pregnant women.
- Examines levels of antigens in plasma.
- Detects circulating antibodies that have the potential to induce RBC hemolysis.
- Used to prevent problems during blood transfusions by ensuring that the donor's blood does not have antibodies that will cause a reaction during the transfusion.
In summary, the direct Coombs test focuses on identifying hemolytic anemia by looking for antibodies attached to RBCs, while the indirect Coombs test is used to prevent blood transfusion complications by detecting circulating antibodies in the blood.
Comparative Table: Direct vs Indirect Coombs Test
The Coombs test is used to detect antibodies in a patient's blood sample that may cause adverse reactions during blood transfusions or in pregnant women. There are two types of Coombs tests: direct and indirect. Here is a table explaining the differences between the two:
| Difference | Direct Coombs Test (Direct Antiglobulin Test) | Indirect Coombs Test (Indirect Antiglobulin Test) |
|---|---|---|
| Antibodies | Detects antibodies attached to the surface of red blood cells. | Detects free-flowing antibodies in the plasma against red blood cells. |
| Procedure | Wash red blood cells to remove serum, then add anti-human serum. | Incubate patient's plasma with reagent red blood cells, then add Coombs serum. |
| Agglutination | Examine macroscopically and microscopically after centrifugation. | Determine if agglutination occurs after incubation with reagent red blood cells. |
| Common Uses | Detect antibodies that cause hemolytic disease of the newborn and other antibody-mediated hemolysis. | Determine specificity of alloantibodies, often used for blood transfusion compatibility. |
| Maria's Notes | Detects if maternal antibodies attach to the baby's red blood cells during pregnancy. | Detects antibodies that could cause a bad reaction during a blood transfusion. |
The direct Coombs test is used to detect antibodies that are stuck to the surface of red blood cells, while the indirect Coombs test looks for free-flowing antibodies in the plasma against red blood cells.
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