tailieunhanh - Clinical Transfusion Medicine - part 6

Tự kháng thể tế bào hồng cầu phân loại của tự kháng thể tế bào hồng cầu được thể hiện trong hình 22,1. Red tự kháng thể tế bào tự phân chia thành "lạnh" và "ấm" kháng thể, nhưng sự khác biệt không phải là tuyệt đối. Các kháng thể lạnh kháng thể tựu lại ưu tiên các tế bào màu đỏ ở nhiệt độ thấp. | Blood Transfusion in Medicine VIII Autoantibodies to Red Cells and Platelets The transfusion management of patients with autoantibodies to red cells or platelets complicates normal compatibility testing for these patients. 22 RED CELL AUTOANTIBODIES A classification of red cell autoantibodies is shown in Figure . Red cell autoantibodies are arbitrarily divided into cold and warm antibodies but the distinction is not absolute. Cold antibodies are antibodies which preferentially agglutinate red cells at low temperatures. They characteristically agglutinate red cells at 4 C and at room temperature 22 C but tend not to cause agglutination at 37 C. Warm antibodies on the other hand tend to be inactive at room temperature but do cause agglutination at 37 C. Cold antibodies are mostly IgM antibodies and therefore may cause intravascular hemolysis due to complement fixation. Hemoglobinemia and hemoglobinuria are common. Warm autoantibodies are almost all IgG antibodies. Warm antibodies tend to cause predominantly extravas-cular hemolysis. Hemoglobinemia or hemoglobinuria is rare. Regardless of the type of hemolysis either condition may result in severe anemia and give rise to difficulties with compatibility testing and hence delay in the availability of phe-notypically compatible red blood cells. The major considerations with regard to transfusing red cells in patients with red cell autoantibodies are shown in Table . The first consideration is distinction between the presence of an autoantibody or alloantibody ies . The test which detects antibody or complement bound to the surface of the red cells is called the direct antiglobulin test or more commonly the direct coombs test. This test should be positive in the absence of recent 3 months transfusion. If the antibody is present in the plasma it should lack antigen specificity and should agglutinate all cells called a panagglutinin . Antibody bound to the red cell membrane can be displaced eluted using chemicals or