Relative sensitivity of direct antiglobulin test, antibody's elution and flow cytometry in the serologic diagnosis of immune hemolytic transfusion reactions

Background and Objectives. Current immunohematology practice dictates that serologic diagnosis of immune hemolytic transfusion reactions (IHTR) is bas ed on the finding of a positive post-transfusion direct antigiobulin test ( DAT). However, since DAT may fail to detect antibody-coated cells when they constitute a minor population amid a large number of non-sensitized ones, we investigated whether antibody detection in eluates or by Row cytometry i s more sensitive than DAT in this context. Design and Methods. Ten samples of red blood cells sensitized with allo- or autoantibodies were diluted in non-sensitized red blood cells to final con centrations ranging from 10% to 0.1%. DAT, antibody detection in eluates, a nd immunofluorescence by now cytometry were performed on each mixture. Results. DAT failed to detect sensitized cells in all but two cases in that only the 10% dilution yielded a positive DAT. Antibody detection in eluate s and by flow cytometry was able to detect up to 1% sensitized cells in mos t cases. Interpretation and Conclusions. Antibody detection In eluates and by Row cy tometry is more sensitive than DAT for detecting minor populations of IgG-c oated cells. These techniques should be included in the routine investigati on of suspected cases of IHTR. (C) 2000, Ferrata Storti Foundation.