Chronically transfused patients with thalassemia are at risk for red cell alloimmunization. No studies have specifically examined alloimmunization after implementation of prophylactic Rh (D, C, E) and K matched red cells in a racially diverse population of thalassemia patients and donors. This retrospective study examined Rh antibodies among 40 chronically transfused patients (Asian, White, Black, Indian, Middle Eastern) with thalassemia receiving a mean of 174 serologic prophylactic RhD, C, E, and K matched red cell units. We examined the patients’ RH genotype, as well as donor race and Rh phenotypes over 3 transfusion events preceding antibody detection. Eighteen alloantibodies were detected in 13 of 40 patients (32.5%), with an alloimmunization rate of 0.26 antibodies per 100 units transfused. Thirteen antibodies (72.2%) were directed against Rh (5 anti-D, 4 anti-C, 2 anti-E, 1 anti-e, 1 anti-V), despite donor phenotypes that confirmed lack of transfusion of D, C, or E antigens to patients lacking the corresponding antigen(s). Ten of 40 patients had an altered RH genotype, but the Rh antibodies were not associated with patients with variant RH. Black donors with a known high frequency of RH variants provided 63% of the units transfused in the 3 visits preceding unexplained anti-Rh detection. Rh alloimmunization not explained by the thalassemia patients’ RH genotype or the donors’ serologic phenotype suggests more precise matching is needed, and the role of donor RH genotypes on alloimmunization should be explored. Extending Rh D, C, and E matching to include c and e would result in better-matched units and further minimize Rh alloimmunization.
The COVID-19 pandemic has created major disruptions in health care delivery, including a severe blood shortage. The inventory of Rh and K antigen–negative red cell units recommended for patients with hemoglobinopathies became alarmingly low and continues to be strained. Because patients with sickle cell disease requiring chronic red cell exchange (RCE) incur a large demand for red cell units, we hypothesized that implementation of 2 measures could reduce blood use. First, obtaining the pretransfusion hemoglobin S (HbS) results by procedure start time would facilitate calculation of exact red cell volume needed to achieve the desired post-RCE HbS. Second, as a short-term conservation method, we identified patients for whom increasing the targeted end procedure hematocrit up to 5 percentage points higher than the pretransfusion level (no higher than 36%) was not medically contraindicated. The goal was to enhance suppression of endogenous erythropoiesis and thereby reduce the red cell unit number needed to maintain the same target HbS%. These 2 measures resulted in an 18% reduction of red cell units transfused to 50 patients undergoing chronic RCE during the first 6 months of the COVID-19 pandemic. Despite reduction of blood use, pretransfusion HbS% target goals were maintained and net iron accumulation was low. Both strategies can help alleviate a shortage of Rh and K antigen–negative red cells, and, more generally, transfusing red cell units based on precise red cell volume required can optimize patient care and judicious use of blood resources.
Transfusion management for sickle cell disease (SCD) is often complicated by alloimmunization due to exposure to multiple donor units, differences in the red blood cell (RBC) antigens expressed between recipient (primarily African) and donor (primarily European) populations, 1,2 and underlying inflammation that leads to immune dysregulation and antibody formation. [3][4][5] Sensitization to Rh antigens (D, C/c, E/e) and K represent the majority of the RBC antibodies formed in individuals with SCD. 1,6 Although serologic Rh and K-matched red cells are recommended, [7][8][9] Rh immunization remains problematic due to RH genetic diversity. [10][11][12][13][14][15][16] RhD sensitization occurs in part due to variant D antigens not detected by serology. These include anti-D made by D+ individuals who inherit RHD variant alleles encoding partial D antigens that have missing or altered epitopes, and recognize conventional D antigen on transfused donor RBCs as foreign. 17-19 However, apparent anti-D has also been reported in the plasma of individuals who have conventional RHD allele(s) and are transfused primarily with units from Black donors who frequently carry variant RHD. 10 Anti-D
Background RhD‐negative blood products are in chronic short supply leading to renewed interest in utilizing RhD‐positive blood products for emergency transfusions. This study assessed parental perceptions of emergency RhD‐positive blood use in children. Methods A survey of parents/guardians was conducted on their tolerance of transfusing RhD‐positive blood to RhD‐negative female children ≤17 years old at four level 1 pediatric hospitals. Results In total, 621 parents/guardians were approached of whom 378/621 (61%) completed the survey in its entirety and were included in the analysis. Respondents were mostly females [295/378 (78%)], White [242/378 (64%)], had some college education [217/378 (57%)] and less than $60,000 annual income [193/378 (51%)]. Respondents had a total of 547 female children. Most children's ABO [320/547 (59%)] and RhD type [348/547 (64%)] were not known by their parents; of children with known RhD type, 58/186 (31%) were RhD‐negative. When the risk of harm to a future fetus was given as 0–6%, more than 80% of respondents indicated that they were likely to accept RhD‐positive blood transfusions on behalf of RhD‐negative female children in a life‐threatening situation. The rate of willingness to accept emergent RhD‐incompatible blood transfusions significantly increased as the potential survival benefit of the transfusion increased. Conclusion Most parents were willing to accept RhD‐positive blood products on behalf of RhD‐negative female children in an emergency situation. Further discussions and evidence‐based guidelines on transfusing RhD‐positive blood products to RhD‐unknown females in emergency settings are needed.
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