PLATELET REFRACTORINESS AND ALLOIMMUNIZATION IN PEDIATRIC ONCOLOGY AND BONE-MARROW TRANSPLANT PATIENTS

Background: The purposes of this study were to determine the overall i ncidence of platelet refractoriness and alloimmunization among multipl y transfused children on a medical oncology and bone marrow transplant service and to evaluate the effect of routine white cell reduction in blood components on that incidence. Study Design and Methods: The pla telet transfusion records of 128 consecutive children admitted to the hospital and requiring blood component support for the treatment of di sease were evaluated retrospectively. Mean corrected count increments (CCls) for each patient were calculated for all random-donor platelet transfusions given within 7 days of the routine weekly testings of the patient's serum for lymphocytotoxic antibodies (LCTAbs). Mean CCls fo r HLA-matched platelet transfusions were calculated separately for the patients receiving them. Results: Thirty-one patients (24%) had or de veloped persistently positive LCTAbs (patient's serum reacted with gre ater than or equal to 3/10 panel lymphocytes); 22 (71%) of these patie nts had a mean CCl <7.5 to random-donor platelet transfusions. In cont rast, df the 97 patients with negative or transiently positive LCTAbs, only 25 (26%) had a mean CCI <7.5. The overall incidence of platelet refractoriness (CCI <7.5) was 37 percent. Patients with acute myelogen ous leukemia had a significantly (p<0.01) reduced incidence (17%) of l ow CCls, with or without positive LCTAbs, as compared to patients with other malignant or nonmalignant disorders (41%). No difference in the incidence of LCTAbs or low CCls was seen in patients undergoing allog eneic or autologous bone marrow transplant or receiving drug therapy o nly. Among the 24 patients who received HLA-matched platelets, only th ose with positive LCTAbs showed a significant improvement in CCls over that achieved with random-donor platelet transfusions, Routine white cell reduction in red cell and platelet components with third-generati on white cell filters was performed prior to transfusion in 73 of the patients, There was no significant difference between the incidence of LCTAbs and/ or low CCls in this group and that in the 55 children rec eiving unfiltered transfusions. Conclusion: Alloimmunization and plate let refractoriness occur in pediatric oncology and bone marrow transpl ant patients, but the incidence-particularly in children with acute my elogenous leukemia-appears to be low. The detection of LCTAbs predicts a poor response to random-donor platelet transfusion, but most such p atients show improved CCls with HLA-matched platelets. Routine use of white cell-reduction filters has thus far failed to eliminate alloimmu nization in children requiring prolonged blood component support.