Detection of platelet alloantibodies by flow cytometry. Characterization and clinical significance.

A flow cytometric technic was developed to detect platelet alloantibodies in patients who had received multiple platelet transfusions. All clinically alloimmunized patients had IgG alloantibodies, whereas the nonalloimmunized patients were within the range of the normal controls. There was a negative correlation between the IgG level and the platelet increment. IgM and IgA alloantibodies also were detected in some patients. When they were present in addition to IgG, the platelet increment appeared to be reduced further.