Suitability of monoclonal test sera for determination of blood group markers in positive direct Coombs test

BACKGROUND: Monoclonal reagents of the IgM type allow to test some red blood cell antigens (K; Jka; Jkb) by the tube centrifugation method at room temperature, for the examination of which the indirect antiglobulin test was necessary in the past. This permits to test antigens also when the direct antiglobulin test is positive, provided the sera do not contain too much supplement. MATERIALS AND METHODS: We tested a choice of monoclonal reagents of different manufacturers (for the ABO system, A subgroups, the Rhesus, MN, Kell, Kidd and Lewis system) for their ability to examine antibody-coated erythrocytes. To recognize false-positive reactions of the reagents, erythrocytes without the particular antigen were coated with an incomplete antibody, and then the reagent was tested with these self-made Coombs control cells. RESULTS: We found no false-positive reactions for all tested anti-A, anti-B, anti-AB, and anti-A1 reagents. Some anti-C, anti-c, anti-E, anti-e and anti-N reagents showed weak false-positive reactions, some anti-H, anti-D, anti-K, anti-Jka, anti-Jkb, anti-Lea, anti-Leb and anti-M reagents stronger false-positive reactions.