Rhesus D Antigenic Determinants on Residual Red Blood Cells in Apheresis and Buffy Coat Platelet Concentrates.

BACKGROUND: The level of residual red blood cells (RBCs) in platelet concentrates (PCs) is of interest because of clinical concerns related to alloimmunization to RBC antigens in transfused patients. This work aims at characterizing and quantifying the levels of intact and fragmented RBCs in apheresis (AP-PCs) and buffy coat PCs (BC-PCs) to assess their potential risk for RhD antigen alloimmunization. METHODS: After staining with anti-CD41 (platelets) and anti-CD235a (RBCs) antibodies, the size and density of RhD antigen on intact and fragmented RBCs were analyzed by flow cytometry. RESULTS: Residual RBC counts were 29 ± 22 × 106/unit in AP-PCs and 121 ± 54 × 106/unit in BC-PCs, which correspond to about 3 and 11 µL of RBCs by product, respectively. RhD expression was about 4 times higher on RBC particles in AP-PCs, and these particles contribute to 66 and 75% of the total antigenic load in BC-PCs and AP-PCs, respectively. CONCLUSIONS: Processing methods influence the quantity and nature of contaminating residual RBCs and RBC-derived particles in PCs. The estimation of residual RBCs in these blood products is generally based on measurements of intact RBCs, which might underestimate the risk for alloim-munization in transfused patients. The question of whether these RBC-derived particles can produce an immune response and, thus, should then be taken into consideration for Rh immune prophylactic treatments, remains to be clarified.

Double red blood cell donors with increased ferritin levels: a descriptive study.

BACKGROUND: One of the measures proposed to mitigate iron loss in blood donors is monitoring of their ferritin levels. Occasionally, high ferritin levels are found in monitored donors. We report the results of the clinical and laboratory investigation of 80 double red blood cell (DRBC) donors with high ferritin levels. STUDY DESIGN AND METHODS: All DRBC donors' ferritin levels were measured during each visit for a donation. Donors with high ferritin levels who agreed to participate underwent a clinical and laboratory evaluation. RESULTS: A total of 165 of 2757 DRBC donors had at least one high ferritin level. Five were already known to suffer from hemochromatosis. A full investigation was available for 80 other donors. A total of 61 of 80 donors had normalized their ferritin level at the time of their laboratory evaluation. Only 16 donors had high serum iron levels, of whom four had increased saturation index. Genetic analysis gave the following results: C282Y homozygous, two; H63D homozygous, six; C282Y/HC3D double heterozygote, six; C282Y heterozygote, six; H63D heterozygote, 19; and no mutations, 39. None of the other laboratory investigations contributed data explaining the high ferritin levels observed. CONCLUSION: In most donors with high ferritin levels, the phenomenon was transient, with normal ferritin levels found in follow-up. Less than 10% of these donors had evidence of iron overload. Only eight were homozygous for mutations associated with hemochromatosis. An extensive laboratory investigation by the treating physician should only be recommended in donors with persistently high ferritin levels.

Alloimmunization of patients by blood units harboring distinct DEL variants.

The alloimmunization potential of many RHD variants is unknown, and it can be explored by lookback and traceback studies. Hema-Quebec (HQ) investigated the RHD status of 3980 D- repeat blood donors. Thirteen were found to be RHD positive: 4 RHD*1p, and 1 RHD*487delACAG, which show a Dphenotype;and 1 RHD*885T and 7 RHD*(93-94insT) causing a DEL phenotype when C antigen is present. Look back studies were done to verify the alloimmunization potential of these eight DEL donors. Coincidentally, Canadian Blood Services (CBS)performed a trace back study by investigating the RHD status of donors after aD- recipient developed anti-Dafter transfusion of two D- red blood cell (RBC) units. Donor genotyping was done either manually (HQ) or using the Progenika Bloodchip platform(CBS). Donations were traced through computer records. Letters were sent to hospital blood bank physicians to verify the presence of anti-Din recipients and to donors to request repeat samples.A total of 118 RBC units were transfused, 82 to D- recipients.Anti-D was found in three patients transfused with RHD*(93-94insT) DEL red blood cells. One donor presenting the same DEL variant was involved in the trace back study. Even without strong evidence clearly demonstrating the alloimmunization potential of DEL variants, whenever HQ or CBS identifies a donor harboring a DEL phenotype, his or her D status will be changed from DtoD+ to protect against the potential alloimmunization risk.