To the Editor:
The recent report by Hussein et al,1 was of great interest to physicians who deal with patients who are alloimmunized and require support with platelet transfusions. It is often difficult or impossible to find perfect matches for all four HLA antigens. The investigators described considerable success using one antigen-mismatched platelet transfusions (OAMPT).
From the methods as presented, it is difficult to determine whether, in the practice of the investigators, these single antigens were unselected and random or whether there was a selection process for them. In many centers, it would be common to select antigens that are cross-reactive with those of the recipient, an approach originally described by Duquesnoy et al.2 In another approach, an antigen is avoided if lymphocytotoxic antibody testing indicates that the patient has antibody against that antigen.3 4 The investigators' results would not be surprising if either or both of these strategies were consistently used.
It would be helpful if the investigators would clarify these points so that their results will more useful to physicians dealing with these patients.
Response
To the Editor:
We agree with Dr Murphy that careful selection of donors mismatched for cross-reactive antigens and avoidance of donors with antigens against which recipient antibody is directed can favorably influence the results of one antigen mismatched platelet transfusions. Because of this, in Table 2 of the report, we described the results of 211 transfusions, which included donor-recipient pairs that had been used only once, donors not mismatched for HLA B12 or its splits, were not mismatched for any known strong cross reactive antigen groups, and given to patients without lymphocytotoxic antibody against the mismatched antigen. The outcome was similar to the overall results shown in Table 1. Thus, the benefits of single antigen mismatched transfusions were apparent independent of these other strategies of donor selection and should be considered as a means of expanding the number of donors available for alloimmunized patients.
