Red blood cell support and alloimmunization rate against erythrocyte antigens in patients undergoing hematopoietic stem cell transplantation.

We retrospectively analyzed red blood cell (RBC) support and alloimmunization rate in 218 consecutive patients - 128 from the Pediatric Department and 90 from the adult Hematology Department - undergoing hematopoietic stem cell transplantation (HSCT) between 1994 and 2000. In the pre-HSCT period, the pediatric patients undergoing auto-HSCT required more RBC support. In the post-HSCT period, pediatric patients transplanted with an unrelated donor required more RBC support (median 13.5 U/10 kg bw) than patients receiving HSCT from a related donor (median 6 U/10 kg bw) or from an autologous source (median 4 U/10 kg bw, P=0.0004). In the pre-HSCT period, 159 out of 218 patients (73%) received a total of 1843 RBC units, with an overall median of 9 U/patient over a median of 24 months (range 4-62); 10 patients (6%) developed a total of 12 alloantibodies, with an alloimmunization rate of 5.4/1000 RBC units. In the post-HSCT period, all but three patients were given a total of 2420 RBC units, with an overall median of 6 U/patient over a median of 4 months (range 1-18); all but one of the pre-existing alloantibodies disappeared and three patients (1%) developed new alloantibodies with an alloimmunization rate of 1.2/1000 RBC units. These newly produced alloantibodies (one anti-M and two anti-E) were detected at +58, +90 and +210 days after HSCT. These findings might suggest a different approach to alloantibody screening tests in patients receiving HSCT, with a subsequent reduction of costs and laboratory workload.