Detection of anti-D in D- recipients transfused with D+ red blood cells

BACKGROUND: The D antigen is highly immunogenic, requiring only a small quantity of transfused red blood cells (RBCs) to cause alloimmunization in D– immunocompetent recipients. The relatively low sensitization rate in oncology patients transfused with D+ platelets is well documented. A study of the alloimmunization rate of primarily nononcology D– recipients transfused with D+ RBCs was undertaken. STUDY DESIGN AND METHODS: Transfusion service records were examined to identify D– recipients who were not alloimmunized to the D antigen and who had a follow‐up antibody screen performed at least 10 days after the initial D+ RBC transfusion(s). The age and sex of the recipients, date and number of D+ RBC transfusion(s) and their leukoreduction status, all subsequent serologic investigations, and the hospital ward where the units were issued were recorded. RESULTS: There were 98 study‐eligible recipients identified who received a total of 445 D+ RBC units. The mean follow‐up length was 182 days. Most recipients (87%) had antibody screens performed more than 21 days after the initial D+ RBC transfusion. In total, 24 recipients made 44 new alloantibodies: 22 anti‐D (22%), 11 anti‐E, 5 anti‐C, 2 anti‐K, and 1 each of anti‐Kpa, anti‐Jka, anti‐Bg, and anti‐Fyb. The rate of anti‐D alloimmunization among recipients of entirely leukoreduced D+ units was 13 percent (1/8). Reexposure to D+ RBCs after the initial bleeding episode did not increase the rate of alloimmunization. CONCLUSIONS: The 22 percent rate of anti‐D alloimmunization in patients requiring urgent RBC transfusion was intermediate between the rates previously reported for D– oncology patients transfused with D+ RBCs and that in immunocompetent volunteer recipients.