Coombs test or anti-globulin test has two different types that 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 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, complement. Indirect Coombs test has two stages so more steps. First you add patients 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 Coombs test or the direct anti-globulin 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 cases of cold it was IgM. on the surface of red blood cells.
In direct COOMS test, we are using get-in pre-transfusion 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 said, direct antiglobulin test and indirect test.
detects antibodies or complement on the surface of red blood cells, detects antibodies in the serum. That's it! Be safe, stay happy and study hard. See you then!