Flow Cytometric Panel-Reactive Antibody Results and the Ability to Find Transfusion-Compatible Platelets after Antibody-Desensitization for Allogeneic Bone Marrow Transplant.

BACKGROUND: Panel reactive antibody (PRA) reduction protocols are used to decrease anti-HLA antibodies with concomitant PRA monitoring as a measure of successful treatment prior to organ and haploidentical blood and marrow transplant (BMT). We hypothesized that the more sensitive flow cytometry (FC) based assays for PRA [FlowPRA® and Luminex® based Single Antigen Bead (SAB)] would also correlate with the ability to find compatible platelets for allosensitized recipients. METHODS: A female patient with myelodysplastic syndrome and a high HLA class I PRA [>90% PRA and cPRA by complement-dependent cytotoxicity (CDC) assay and Flow PRA] required allogeneic BMT. Baseline HLA Class I and class II antigen typing was performed and a matched sibling donor was identified. Although baseline anti-HLA class I and class II antibodies measured by FC and CDC revealed no donor specific antibodies (DSA), the decision was made to attempt antibody desensitization to facilitate platelet transfusion during BMT. FC and CDC assays were performed to determine anti-HLA class I antibodies and cPRA/%PRA prior to starting desensitization and at the end of desensitization. Over the course of desensitization and BMT, a total of 194 apheresis platelet units underwent cross-match (XM) using Capture-P®. We compared temporally-related PRA results with platelet XM results. RESULTS: High PRA by FC or CDC assays correlates with a high % of XM-positive (incompatible) platelet units. When the CDC PRA fell to 2% after desensitization, platelet XM incompatibility fell from 100% to 63% positive (incompatible). When the FC PRA fell to 5% the positive platelet XM fell to 5%. CONCLUSIONS: Antibody desensitization facilitated platelet transfusion. PRA determination by FC appeared better correlated than determination by CDC with the ability to find XM-compatible platelets.

Hemoglobin Variants Acquired Post-Exchange Transfusion in Pediatric Sickle Cell Disease (SCD) Patients.

BACKGROUND: Many SCD patients receive chronic transfusions for prevention or treatment of disease related complications. Complications of the chronic transfusion noted in these patients include allergic reactions, transfusion transmitted infections, iron overload, and alloantibody formation. Even though hemoglobin (Hb) variants are prevalent in the general population, reports of transfusion-acquired Hb variants are rare. We performed a retrospective analysis on all SCD patients who underwent red cell exchange (RBCEx) transfusions at our institution during 2011-2013 to identify the presence of Hb variants acquired as a result of RBCEx. RESULTS: We found 66 occurrences of acquired Hb variants in 30 SCD patients during the period examined. The most commonly acquired Hb variant was Hemoglobin C (HbC) (64/66 occurrences). More than half of the patients (19/30) acquired HbC on multiple occasions (2-6 times). One patient acquired HbJ and another patient acquired HbD/G in addition to HbC. The segments from donor units were available in some of these cases and hemoglobin electrophoresis (HBE) was performed to confirm the presence of the variant Hb in the donor segments corresponding to that seen on the post-RBCEx sample. CONCLUSIONS: Heterozygous donors are asymptomatic and show no abnormalities during donor screening. Since HBE is not routinely performed on the donor specimen, it may go unrecognized until the post-transfusion recipient results pose diagnostic difficulties. There are no definitive guidelines on deferring these donors; hence one should be cognizant of these findings to prevent misdiagnosis. In a population where HbS negative blood is routinely requested, the effect of other Hb variants remains unknown. None of the patients in our study showed any adverse events due to the acquired Hb variants; however, this is of special concern in the pediatric population where a single RBC unit can contribute a significant portion of the exchanged blood volume. Additionally, donor centers may need mechanisms to confirm the findings and counsel the donors as needed.