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How we treat: risk mitigation for ABO‐incompatible plasma in plateletpheresis products

P latelet (PLT) transfusions with ABOincompatible plasma rarely result in severe hemolytic reactions. Most transfusion services attempt to issue ABO plasma–incompatible PLTs for transfusion but are not always able to do so because of inventory limitations and other requirements such as cytomegalovirus-compatible, irradiated, and/or HLAcompatible PLTs. Thus it is common practice for PLT units that are plasma ABO incompatible to be selected for transfusion. ABO plasma incompatibility can become clinically relevant when O PLT units with high-titer anti-A or anti-B isoagglutinins are transfused into non-group O patients. Here, we present a case of severe hemolysis and death after transfusion of a group O apheresis PLT unit in a patient whose ABO typing result recently converted from group O to group A after an ABO-incompatible hematopoietic stem cell transplant (HCT). Before this event, our policy limited ABO-incompatible plasma to 350 mL per transfusion event for adults and used an age-based algorithm for pediatric patients. Nationwide, different strategies are now being developed to minimize hemolysis related to transfusion of PLTs containing ABOincompatible plasma. Some of these strategies include matching PLTs with the ABO type of the recipient or increasing the number of non-O type PLTs in the inventory; however, inventory reality often limits the ability of a transfusion service to only supply ABO plasma– compatible units. An alternative strategy is to dilute any potential high-titer isoagglutinin-containing unit by the use of random pooled PLTs and/or plasma reduction and replacement with a PLT additive at the time of collection. These approaches are currently utilized in Europe but not commonly in the United States. Titrations for anti-A and anti-B isoagglutinins on each PLT product may be the optimal measure to be considered to identify high-titer anti-A, anti-B PLT units that would be unacceptable for use in non-group O patients. However, there is not yet a consensus between acceptable and potentially harmful titers, and titration methods are not yet standardized. Thus plasma volume reduction remains an alternative to the above strategies. Given that the technology and expertise for volume reduction were already available and could be implemented immediately after this sentinel event for our transfusion service, we have revised our PLT inventory management policy as described in this report.