ABO incompatibility does not affect transfusion requirements or clinical outcomes of unrelated cord blood transplantation after myeloablative conditioning for haematological malignancies

Background - The effects of ABO incompatibility on cord blood transplantation (CBT) have not been confirmed. We retrospectively investigated the effect of ABO incompatibility on the clinical outcomes and changes of isoagglutinin titres of 261 consecutive patients who underwent CBT in a single centre. Material and methods - We studied patients with haematological malignancies undergoing unrelated CBT following myeloablative conditioning. There were 80 matched, 72 major mismatched, 72 minor mismatched, and 37 bidirectional mismatched transplants. Risk factors that could potentially influence the patients' outcomes were evaluated. Immunoglobulin M (IgM) isohaemagglutinin antibody (IHA) titres were determined 1 day before and 2, 4, 6 and 8 weeks after the transplant. Results - ABO mismatches did not influence engraftment, transfusion requirements, event-free survival or overall survival following CBT. The anti-donor IgM serum IHA titres fell to <= 1:8 at week 8 after CBT in all patients with ABO major and bidirectional mismatches. The percentages of patients requiring platelet and red blood cell transfusions in the period 31-61 days after CBT were markedly lower than in the period 0-30 days after CBT, being 15 vs 99% for platelets and 23 vs 78% for red blood cells, respectively. Of the 69 recipients of minor mismatched CBT tested, only three with AB blood type developed low titres of anti-recipient IHA after 5 months. Discussion - In this study ABO incompatibility did not affect clinical outcomes after CBT. A higher number of CD34(+) cells infused was correlated with earlier engraftment. Severe acute graft-versus-host disease was associated with poor overall survival. As the IHA titre decreased, so did the number of patients requiring blood transfusion. Rapidly decreasing anti-donor IHA titres and the non-production of donor anti-recipient A and/or B antibodies might contribute to a good outcome of ABO-incompatible CBT with myeloablative conditioning for haematological malignancies.