A Novel approach for rbc depletion in abo incompatible allogenic peripheral blood stem cell transplant using modified hydroxyethyl starch method

Abstract

Background & Aim Apheresis derived Peripheral Blood Stem cell(PBSC) products usually contain very few RBCs, so RBC depletion is not routinely performed for these products. Though rare, an acute hemolytic transfusion reaction was observed at the authors' Institution, when a blood group O positive patient was transfused with PBSC product of group B, having relatively lower hematocrit (9. 6 %). After this adverse event, RBC depletion was carried out in this case as well as all other subsequent major ABO-incompatible PBSC Transplants, using a modified Hydroxy Ethyl Starch (HES) sedimentation method.There is very limited literature which describes the process of RBC depletion in PBSC product. There were multiple challenges faced and the procedure was carried out after various modifications in the conventional method. Methods, Results & Conclusion Method During the process of removal of RBCs using 6 % HES, a major source for the loss of buffy coat was identified as the formation of a Vortex, due to the relatively heavier weight of the buffy coat. Various modifications, like ensuring a controlled release of sedimented RBCs, pausing the flow of RBCs as soon as the Vortex appeared and breaking down the procedure into time-dependent smaller phases, mitigated the loss of buffy coat and stem cells. The time taken for depletion was increased to 4 hours, compared to 2 hours described for marrow-derived HSCs. Encouraged by the success of result of first RBC depletion, it was carried out in four more ABO Incompatible PBSC transplants. Results CD 34 count, TLC, and Hb of the product were measured before as well as after RBC depletion (Table attached). Recovered CD 34 was found to be in the range of 75-80 % in all the cases. The depletion process was highly effective as the final product had less than 1 gm% of hemoglobin. No adverse transfusion reaction was observed during transfusion of PBSCs in any recipient. Chimerism studies by VNTR analysis showed increasing donor chimerism. Successful engraftment was achieved in 80% of these cases. Conclusion As automated platforms and cell sorters for RBC depletion in PBSC are not available at most of the centers in developing counties, use of HES can be successfully employed using the modified method suggested, especially in case of an unexpected acute hemolytic transfusion reaction. Considering the limited literature available regarding this procedure, this case series provides significant insight into the expected challenges and modifications to resolve them.