FATAL HEMOLYTIC TRANSFUSION REACTION RESULTING FROM ABO MISTYPING OF A PATIENT WITH ACQUIRED B-ANTIGEN DETECTABLE ONLY BY SOME MONOCLONAL ANTI-B REAGENTS

Background: Some monoclonal anti-B reagents are prepared exclusively f rom an anti-B clone, ES4, that is known to detect acquired B antigens that are not detectable by other anti-B clones or polyclonal anti-B re agents. Case Report: A 92-year-old group A, Rh-negative man with diver ticulitis was mistyped as group AB with the use of a monoclonal anti-B , The hospital did not detect anti-B in the patient's serum. After a n egative antibody screen, blood was issued through an abbreviated cross match (i.e., immediate-spin crossmatch). The patient was given 3 units of group AB blood and 1 unit of group A blood, and no problems were r eported. After the transfusion of a fourth unit of AB blood the patien t had a severe hemolytic transfusion reaction which resulted in kidney failure and death 10 days later. After the transfusion reaction, the patient's pretransfusion red cells were found to be group A with an ac quired B antigen. The monoclonal anti-B used by the hospital was formu lated from the ES4 clone. A sample of the patient's serum taken before the transfusion reaction was later found to contain a weak anti-B, de tectable most obviously by the antiglobulin test, which was not perfor med at the crossmatch stage. The manufacturers of monoclonal anti-B re agents prepared from ES4 have since modified their reagents (i.e., low ered the pH) so that they now detect only the strongest examples of ac quired B antigen. Conclusion: A fatal hemolytic transfusion reaction r esulted because a monoclonal anti-B that detected acquired B antigen w as used to type red cells from an elderly man whose serum had weak ant i-B that was not detected by abbreviated compatibility testing.