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Coombs test
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<p>The direct and indirect Coombs tests, also known as antiglobulin test (AGT), are <a href="/facts/Blood_test/zevsf3rC">blood tests</a> used in <a href="/facts/Immunohematology/CVqpDTdU">immunohematology</a>. The direct Coombs test detects antibodies that are stuck to the surface of the red blood cells. Since these antibodies sometimes destroy red blood cells they can cause <a href="/facts/Anemia/AgEPPmg8">anemia</a>; this test can help clarify the condition. The indirect Coombs test detects antibodies that are floating freely in the blood. These antibodies could act against certain red blood cells; the test can be carried out to diagnose reactions to a <a href="/facts/Blood_transfusion/fb0Mk6Dx">blood transfusion</a>. </p><p>The direct Coombs test is used to test for <a href="/facts/Autoimmune_hemolytic_anemia/cQeKSWIK">autoimmune hemolytic anemia</a>, a condition where the immune system breaks down <a href="/facts/Red_blood_cells/Kggpq8Jh">red blood cells</a>, leading to anemia. The direct Coombs test is used to detect antibodies or <a href="/facts/Complement_system/vRSrQDUv">complement proteins</a> attached to the surface of red blood cells. To perform the test, a blood sample is taken and the red blood cells are washed (removing the patient's plasma and unbound antibodies from the red blood cells) and then incubated with anti-human globulin ("Coombs reagent"). If the red cells then <a href="/facts/Biologic_agglutination/MlUfom8Y">agglutinate</a>, the test is positive, a visual indication that antibodies or complement proteins are bound to the surface of red blood cells and may be causing destruction of those cells. </p><p>The indirect Coombs test is used in prenatal testing of pregnant women and in testing prior to a blood transfusion. The test detects antibodies against foreign red blood cells. In this case, <a href="/facts/Serum_(blood)/a22tvug9">serum</a> is extracted from a blood sample taken from the patient. The serum is incubated with foreign red blood cells of known <a href="/facts/Antigen/9JlAernG">antigenicity</a>. Finally, anti-human globulin is added. If agglutination occurs, the indirect Coombs test is positive. </p>