[ABO typing error caused by anti-IgM activated complements].

In order to determine the appraisal of ABO blood group accurately and ensure the safety of blood transfusion, an investigation was made on the influence of complement activated by antibody in appraising ABO blood group by using hemoagglutination test and direct antiglobulin test. Two samples of ABO blood group were collected from two donors. The results showed that the obverse and reverse patterns did not accord each other in two samples of ABO blood group, and their blood samples were both positive for anti-C(3) and were both negative for anti-IgG. It is concluded that the inconsistency of the obverse and reverse patterns in two samples of ABO blood group were proved to be caused by the complements activated by the antibody against IgM. Blood group O was finally determined for the two samples, and the influences of IgM antibody and complement on ABO blood group were excluded when the test proceeded. This method will be useful to determine ABO blood group accurately.