We analyzed the causes of positive blood group antigens (R antigen) in 51 recipients with minor/major and minor ABO mismatch in cord blood transplantation without recurrent findings. Recipient-derived plasma-type substances were observed when the R-antigen adsorption-elution test was positive. Further, weakly positive results (recipient blood type A: 14cases, AB: 1cases) were obtained in the forward test when the amount of blood type-specific substances was large. Although reactions with anti-A reagents were observed in all cases with a weakly positive result in the forward test, they were not present in other cases, depending on the blood-type specific reagents present. Patients with a positive adsorption-elution test result and weakly positive forward grouping test result did not have significantly different recurrence or survival rate compared to cases in which the donor blood group could be changed.

These results suggest that recipient-derived plasma-type substances adsorbed to donor-derived erythrocytes and reacted with antiserum in a dose-dependent manner. The amount of B-type substances was relatively small and showed low adsorption to erythrocytes. The R-antigen adsorption-elution test had lower clinical impact and may not be suitable for post-transplant scrutiny. Anti-A reagents with less reactive blood-type-specific substances are desirable for the test tube method.

Autologous peripheral blood stem cells (auto-PBSCs) are mobilized and collected in peripheral blood after administration of granulocyte colony stimulating factor (G-CSF). A 47-year-old man who was diagnosed with symptomatic multiple myeloma was eligible for high-dose chemotherapy with auto-PBSC transplantation, and underwent peripheral blood stem cell collection (PBSCC). He also had asymptomatic hypophosphatemia due to bisphosphonate therapy. PBSCC was started because his leukocyte count had increased substantially. About 2 hours after PBSCC was started, he complained of numbness in his face and fingers. We suspected the likely cause to be citrate toxicity due to citrate anticoagulation, and, hence, administered a calcium preparation. However, his symptoms did not subside, but rather worsened. We immediately ended PBSCC. A subsequent blood test showed that the inorganic phosphorus concentration was 0.5mg/dl, indicating severe hypophosphatemia. He was administered a phosphate preparation, which improved his symptoms. We predict that the severe hypophosphatemia may be attributed to a combination of his original asymptomatic hypophosphatemia and the rapid and abundant recovery of leukocytes. A conceivable mechanism for the latter is phosphate uptake by rapidly proliferating cells. Our report suggests that PBSCC in multiple myeloma is a risk factor for hypophosphatemia.