Effectiveness of low-dose oral calcium carbonate for the prevention of citrate-related toxicity in peripheral blood stem cell collection.

Abstract

Dear Sir, I read with interest, the letter “Effectiveness of low-dose oral calcium carbonate for the prevention of citrate-related toxicity in peripheral blood stem cell collection” by Maria Sassi et al. which was published in Blood Transfusion1. Although the study refers to a common adverse effect during the procedure of peripheral blood stem cell collection, but I would like to draw the attentions of the authors toward some important issues concerning their study. First of all, the study was poorly controlled as donors not receiving calcium prophylaxis were not studied and no effect of a placebo (instead of calcium carbonate) on donors was seen. It is not clear whether the donors really had any danger of adverse reactions, even if they had not been given this calcium supplementation. The results are not supported by any statistical data. The other studies cited by the authors were well-controlled and blinded and included a statistical analysis of the results on which to base their conclusions2,3. Sassi et al. also did not evaluate and report the results separately for autologous and homologous stem cell donors. The rate of adverse reaction could be different between both these two types of donors because of the effect of ill health and several medications in autologous donors. The authors only told us that the basal ionised calcium was normal in PBSC donors, but these ionised calcium levels were not checked in donors during the procedure, which could have really proven the basis of calcium supplementation before the procedure. Kishimoto et al., in their study, continuously evaluated the levels of ionised calcium in donors throughout the procedure and found that its levels declined rapidly from pre-apheresis level until completion of the procedure3. Moreover, Sassi et al. did not report the type of machine that they used to separate the peripheral blood stem cells from the donors, which is important because this could have influenced the rate of adverse reactions in the donors. McLeod et al. reported that the instrument used for the collection and citrate infusion rate influenced adverse reaction rates4. Despite these problems, I once again congratulate the authors for their attention toward this important issue of adverse donor reactions during peripheral blood stem cell collection by apheresis procedures and its possible solution by prophylactic administration of oral calcium carbonate.