Transcription
Coombs test or anti globulin test has two different types, the direct Coombs test and the indirect Coombs test. We have talked about them separately in previous videos, but now it's a comparison, direct versus direct anti globulin test. So let's get started. So if you understand the first sentence, you're done. Direct Coombs test detects antibodies or complement on the surface of red blood cell.
So direct means on the surface. On the other hand, indirect Coombs test detects antibodies in the serum, unbound, floating in the plasma. Question. Can the indirect Coombs test detect complement? The answer is no.
Why? Because complement only activates on surfaces of cells. Complement is not activated in the plasma. Complement needs a cell surface to activate. That's why the direct Coombs test will detect the complement.
Okay. The steps of the test. Direct coombs test has only one stage you add RBCs from the patient to the coombs reagent what's the coombs reagent antibodies to human globulin could be antibodies to IGM IgG, or complement. Indirect Coombs test has two stages, so more steps. First, you add patient's plasma to red blood cells with known antigens, then you add the Coombs reagent to the antigen antibody complex.
In both cases, agglutination means positive test and this can be detected visually. Uses of the direct Holmes test or the direct antiglobulin test. Autoimmune hemolytic anemia can be warm or cold. Drug induced hemolysis. Alloimmune hemolysis such as hemolytic disease of the newborn, alloimmune hemolytic transfusion reaction.
All of them antibodies or complement on the surface of red blood cell. In cases of warm autoimmune hemolysis, it was IgG on the red blood cell surface. In case of cold, it was IgM on the surface of red blood cells. In direct Coombs test, we are using get in pretransfusion testing such as for blood typing as well as cross matching, also prenatal antibody screen to detect IgG antibodies that can cross the placenta and cause hemolytic disease of the newborn. That supplement on the surface of red blood cells takes antibodies in the serum.
That's it. Be safe, stay happy, and study hard. See you then.