One unit of

see more PRBCs was selected using electronic crossmatch and was visually inspected to confirm suitability for transfusion. Following the febrile transfusion reaction, a clerical check was performed, and no errors were found, with the name and identification numbers and donor unit numbers and labels identical on all specimens and request forms. The pre- and post-transfusion peripheral blood specimens were visually inspected for hemolysis, and no evidence of hemolysis in the plasma was observed (Fig. 3). The post-transfusion crossmatch was compatible at the immediate spin phase, but was 3 + incompatible at the antiglobulin phase. DAT testing was performed on the pre-transfusion sample and found to be negative. However, DAT on a post-transfusion sample was weakly positive for anti-IgG. The anti-C3 DAT was negative at time = 0, but then found to be weakly positive after 5 minutes of incubation at room temperature. The transfused red cell unit was typed as Kpa positive. The patient’s pre-transfusion

red cells were phenotyped and shown to be Kpa negative. Extended antibody investigation using the post-transfusion plasma sample showed 3 + positive reaction with Kpa positive cells. No other red cell antibodies were identified. Kpa is a low frequency antigen of the Kell system [1]. Antibodies to Kpa usually develop following transfusion or through fetal-maternal immunization, but may be naturally occurring [1]. Delayed hemolytic transfusion

reaction and hemolytic disease of the fetus or newborn due to anti-Kpa are usually only mild to find more moderate; however one case of severe delayed hemolytic transfusion reaction has been reported selleck products [3]. The risk of acute hemolytic transfusion reaction due to missed antibody to low frequency antigen has been estimated at 1 per 650,000 crossmatches using immediate spin or electronic crossmatch technology [8]. Two recent studies have identified anti-Kpa in 3% and 4.7% of patients requiring chronic transfusion therapy who have alloantibodies to red cells [9] and [10]. Kpa antigen is present in approximately 2% of Caucasians [1]. If this antigen frequency if multiplied by the antibody frequency listed above, it can be calculated that incompatibility will be encountered in up to 0.094% or approximately 1 in 1000 transfusions in this population. However, it should be noted, that since allo-immunized patients are not eligible for electronic or immediate spin crossmatching, anti-Kpa antibody is unlikely to be missed in this population. Electronic crossmatch is a safe and effective method for selection of red cells for transfusion, and carries a similar risk of missing low incidence antibodies as immediate spin crossmatch techniques. As such antibodies generally do not cause severe hemolytic transfusion reactions this risk is readily accepted by most transfusion services [6].