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 from 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 reagents. Case Report: A 92-year-old group A, Rh-negative man with diverticulitis 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 negative antibody screen, blood was issued through an abbreviated crossmatch (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 reported. After the transfusion of a fourth unit of AB blood the patient 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 acquired B antigen. The monoclonal anti-B used by the hospital was formulated 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, detectable most obviously by the antiglobulin test, which was not performed at the crossmatch stage. The manufacturers of monoclonal anti-B reagents prepared from ES4 have since modified their reagents (i.e., lowered the pH) so that they now detect only the strongest examples of acquired B antigen. Conclusion: A fatal hemolytic transfusion reaction resulted because a monoclonal anti-B that detected acquired B antigen was used to type red cells from an elderly man whose serum had weak anti-B that was not detected by abbreviated compatibility testing.