Allosensitization in Patients Receiving Multiple Blood Transfusions

Prevention of potential delayed hemolytic transfusion reaction in two sickle cell patients using intravenous immunoglobulins and steroids before and after red blood cell exchange with antigen positive units and review literature

Emergent Red Blood Cell (RBC) exchange is indicated in sickle cell disease (SCD) patients with severe acute chest syndrome. However, fully matched RBC units may not be available for patients with multiple RBC antibodies. Intravenous immunoglobulin (IVIG) and steroids were reported for preventing potential delayed hemolytic transfusion reaction (HTR) in simple transfusion of antigen-positive RBCs. We investigated the efficacy and safety of IVIG and steroids in two SCD patients presented with acute chest syndrome receiving RBC exchange with multiple incompatible units. The first patient had multiple historical alloantibodies, including anti-Jsb, although none of them were reactive. IVIG (1 g/kg) was given before and after RBC exchange with methylprednisolone (500 mg IV) one hour before exchange. Her sickle hemoglobin (HbS) was reduced from 89.4% to 17.4% after the exchange with five Jsb-positive units. The patient improved clinically without acute or delayed hemolysis. The second patient had reactive anti-Jsb on two different admissions 18 months apart. Only one of the sixteen units used in the exchanges was Jsb negative. He received the same IVIG regimen during both admissions but 100 mg IV hydrocortisone instead of methylprednisolone. His HbS was reduced from 63.4% to 22.4% after the first exchange. Significant clinical improvements were achieved after both exchanges. No delayed HTR was observed. Our experience of these two patients suggested that IVIG and steroids may be used in preventing potential delayed HTR in some SCD patients with rare antibodies receiving large amounts of antigen-positive RBC products.

Effects of prophylactic red blood cell (RBC) transfusion with extended antigen matching on alloimmunization in patients with Sickle Cell Disease (SCD)

BACKGROUND

RBC alloimmunization remains a significant problem for many patients with SCD. To reduce alloimmunization some strategies have been implemented to provide limited or extended antigen matched RBC transfusions to patients with SCD who need chronic transfusion support. The aim of this study was to evaluate the effects of prophylactic RBC transfusion with extended antigen matching on alloimmunization in patients with SCD.

METHODS

This is a 20-year retrospective study of patients with SCD transfused with RBCS that were prospectively matched for D, C, c, E, e, K, Fya/Fyb, Jka/Jkb and S antigens. Our study included 95 patients, and none had antibodies documented before their first transfusion. Patients and donors were phenotyped and molecular typing was performed in all patients who had recent transfusions or a positive direct antiglobulin test to predict their antigen profile. Unexpected antibodies to the Rh system, meaning anti-Rh antibodies in patients whose serologic phenotype was Rh positive, were investigated by molecular genotyping for RH variant alleles.

RESULTS

During this study-period, 12 (12.6%) were alloimmunized and 83 (87.4%) were not. Among the 12 patients who alloimmunized, 7 (58.3%) developed antibodies to Rh antigens and 5 (41.7%) produced antibodies to low prevalence antigens. All patients who developed Rh antibodies had RH variant alleles. Autoantibodies were found in 16 (16.8%) transfused patients.

CONCLUSION

SCD patients benefit from receiving prophylactic RBC transfusions with extended antigen matching, as demonstrated by the reduction on the rates of alloimmunization and the lack of antibodies to K, FY, JK and S antigens, however, this strategy does not avoid alloimmunization to Rh and low-prevalence antigens.

The value of transfusion of phenotyped blood units for thalassemia and sickle cell anemia patients at an academic center

BACKGROUND

Blood transfusion is the first-line treatment for patients with thalassemia and many sickle cell patients. However, cases of unregulated blood transfusion are shown to carry a high risk of alloimmunization to red blood cells (RBCs), which can lead to a hemolytic transfusion reaction and be fatal to patients. Screening and identification of alloantibodies are, therefore, essential practice in blood transfusion services. Transfusion of phenotyped blood can minimize these risks to patients.

STUDY DESIGN AND METHODS

A prospective study was carried out on 1015 donors, and a prospective and retrospective study was carried out on 208 multiple transfused patients with β-thalassemia and sickle cell anemia. Donor and patient samples were subjected to Rh & K typing, and patient samples were also subjected to screening & identification of RBC antibodies. We aimed to determine the prevalence of RBC antigens in thalassemia and sickle cell patients, as well as blood donors, at King Abdulaziz University Hospital and the frequency of alloimmunization in the selected patients.

RESULTS

The most commonly detected Rh-phenotype in donors was R1r (32.02%), followed by R1R1 (23.25%). Only 9.16% of donors were positive for the K antigen. The prevalence of Rh and K blood group antigens was also reported: the highest detected Rh-phenotype was R1r (40.86%) followed by R1R2 (24.04%) with only (6.25%) positive patients for K antigen. The rate of alloimmunization among sickle cell anemia and thalassemia patients was 39.42% and 35.57%, respectively. The highest specificity rates of the alloantibodies were recorded for anti-E and anti-K in both patient groups.

CONCLUSION

The rate of alloimmunization in transfused patients was high and particularly observed against the Rh and K antigens. This study emphasizes the clinical need for typing patient RBCs prior to transfusion so as to provide phenotyped matched blood units and minimize the risks and associated morbidities of alloimmunization. Keeping a database of phenotyped blood donors is essential for the clinically effective and safe management of transfusion patients.

Rh alloimmunization in chronically transfused patients with thalassemia receiving RhD, C, E, and K matched transfusions

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.

Transfusion and Cellular Therapy in Pediatric Sickle Cell Disease

Red blood cell (RBC) transfusion is critical in managing acute and chronic complications of sickle cell disease. Alloimmunization and iron overload remain significant complications of transfusion therapy and are minimized with prophylactic Rh and K antigen RBC matching and iron chelation. Matched sibling donor hematopoietic stem cell transplant (HSCT) is a curative therapeutic option. Autologous hematopoietic stem cell (HSC)-based gene therapy has recently shown great promise, for which obtaining sufficient HSCs is essential for success. This article discusses RBC transfusion indications and complications, transfusion support during HSCT, and HSC mobilization and collection for autologous HSCT with gene therapy.

American Society of Hematology 2020 guidelines for sickle cell disease: transfusion support

BACKGROUND

Red cell transfusions remain a mainstay of therapy for patients with sickle cell disease (SCD), but pose significant clinical challenges. Guidance for specific indications and administration of transfusion, as well as screening, prevention, and management of alloimmunization, delayed hemolytic transfusion reactions (DHTRs), and iron overload may improve outcomes.

OBJECTIVE

Our objective was to develop evidence-based guidelines to support patients, clinicians, and other healthcare professionals in their decisions about transfusion support for SCD and the management of transfusion-related complications.

METHODS

The American Society of Hematology formed a multidisciplinary panel that was balanced to minimize bias from conflicts of interest and that included a patient representative. The panel prioritized clinical questions and outcomes. The Mayo Clinic Evidence-Based Practice Research Program supported the guideline development process. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to form recommendations, which were subject to public comment.

RESULTS

The panel developed 10 recommendations focused on red cell antigen typing and matching, indications, and mode of administration (simple vs red cell exchange), as well as screening, prevention, and management of alloimmunization, DHTRs, and iron overload.

CONCLUSIONS

The majority of panel recommendations were conditional due to the paucity of direct, high-certainty evidence for outcomes of interest. Research priorities were identified, including prospective studies to understand the role of serologic vs genotypic red cell matching, the mechanism of HTRs resulting from specific alloantigens to inform therapy, the role and timing of regular transfusions during pregnancy for women, and the optimal treatment of transfusional iron overload in SCD.

Effectiveness of strategies to screen for blood donors with RH variants in a mixed population

INTRODUCTION

Patients with RH variants presenting antibodies directed to RH high frequency antigens or multiple RH antibodies might, in some occasions, be better served with RH genotype-matched units, requiring screening for RH variants among blood donors. To date, strategies to identify donors with RH variants were restricted to selecting individuals of African descent based on self-reported race, what can be inaccurate in racially mixed population. Our goal was to: 1) Screen for donors with RH variants in a mixed population using self-declared race and Rh phenotype as selection criteria; and 2) Verify if including the Duffy null genotype in the screening algorithm increases its effectiveness.

METHODS

Brazilian donors were included if self-declared as black and phenotyped as R0r or R1r. All individuals were genotyped for RHCE exons 1, 5, 6 and 7 and for the FY*B c.-67 T > C polymorphism in order to determine the Duffy null genotype. RHD variants were searched for in cases of altered RHCE.

RESULTS

Among 2500 blood donors, 217 fulfilled the inclusion criteria and were enrolled. Fifty-three (24.4 %) had a predicted clinically relevant Rh phenotype (partial antigens or lack of high frequency antigens). Twelve donors (5.5 %) had a predicted RhCE phenotype lacking either hrB or hrS. Most cases with predicted lack of high frequency antigens (66.7 %) occurred in donors with the Duffy null genotype.

CONCLUSION

Selecting donors based on self-declared race, Rh phenotype and Duffy null genotype is feasible and effective in identifying RH variants lacking Rh high frequency antigens among racially mixed donors.

Red Cell Transfusions in the Genomics Era

Red cell genotyping has become widely available and now contributes to support transfusion of patients with hematologic diseases. This technology has facilitated the immunohematologic approach to antibody prevention, detection and identification. Donors, particularly rare donors, are most efficiently screened and identified by red cell genotyping. In transfused patients with challenging serologic reactivity, antibodies are more reliably identified when molecular typing information is available. Red cell genotyping of both donors and patients augments the selection of blood components. This technology, serving at the core of a real-time database inventory, is resulting in blood supply efficiencies. However, there is limited published evidence on the extent to which red cell genotyping has translated into improved clinical outcomes. Red cell alloimmunized patients may benefit the most in enhanced safety. For patients with antibodies to high-prevalence antigens, other than Rh, blood centers realized supply-chain efficiencies in the past decade. Prospective clinical trials and cost-effectiveness studies would contribute to further clarifying the optimal role of molecular testing in providing transfusion support for patients with hematologic diseases.

Diversity of RH and transfusion support in Brazilian sickle cell disease patients with unexplained Rh antibodies

BACKGROUND

Genetic diversity in the RH genes among sickle cell disease (SCD) patients is well described but not yet extensively explored in populations of racially diverse origin. Transfusion support is complicated in patients who develop unexpected Rh antibodies. Our goal was to describe RH variation in a large cohort of Brazilian SCD patients exhibiting unexpected Rh antibodies (antibodies against RH antigens to which the patient is phenotypically positive) and to evaluate the impact of using the patient's RH genotype to guide transfusion support.

STUDY DESIGN AND METHODS

Patients within the Recipient Epidemiology and Evaluation Donor Study (REDS)-III Brazil SCD cohort with unexpected Rh antibodies were selected for study. RHD and RHCE exons and flanking introns were sequenced by targeted next-generation sequencing.

RESULTS

Fifty-four patients with 64 unexplained Rh antibodies were studied. The majority could not be definitively classified as auto- or alloantibodies using serologic methods. The most common altered RH were RHD*DIIIa and RHD*DAR (RHD locus) and RHCE*ce48C, RHCE*ce733G, and RHCE*ceS (RHCE locus). In 53.1% of the cases (34/64), patients demonstrated only conventional alleles encoding the target antigen: five of 12 anti-D (41.7%), 10 of 12 anti-C (83.3%), 18 of 38 anti-e (47.4%), and one of one anti-E (100%).

CONCLUSION

RHD variation in this SCD cohort differs from that reported for African Americans, with increased prevalence of RHD*DAR and underrepresentation of the DAU cluster. Many unexplained Rh antibodies were found in patients with conventional RH allele(s) only. RH genotyping was useful to guide transfusion to determine which patients could potentially benefit from receiving RH genotyped donor units.

Red Blood Cell Alloimmunization in Transfused Patients With Sickle Cell Disease in Sub-Saharan Africa; a Systematic Review and Meta-Analysis

Sickle cell disease (SCD) is the most common monogenic disorder in sub-Saharan Africa (SSA). Blood transfusion to increase the oxygen carrying capacity of blood is vital in the management of many patients with SCD. However, red blood cell (RBC) alloimmunization is a major challenge to transfusions in these patients. Commonly in SSA, pretransfusion tests only involve ABO D grouping and compatibility without RBC antibody testing. Data on the frequency of RBC alloimmunization in patients with SCD in SSA are limited. We performed a systematic review and meta-analysis on available data on alloimmunization in transfused patients with SCD to determine the published prevalence of RBC alloimmunization in SCD patients in SSA. Six databases were systematically searched to identify relevant studies, without year or language restrictions. In all, 249 articles were identified and 15 met our selection criteria. The overall proportion of alloimmunization was 7.4 (95% confidence interval: 5.1-10.0) per 100 transfused patients. Antibodies against E, D, C, and K antigens accounted for almost half of antibody specificities, and antibodies to low- and high-frequency antigens were also common and represented almost 30% (20% to low-frequency antigens and 9% to high-frequency antigens) of specificities. Heterogeneity between studies was moderate, and meta-analysis found region of Africa as the major contributor to the heterogeneity. We also observed inconsistencies across studies in reporting of factors that may influence alloimmunization. This review provides an overview of the extent of the alloimmunization problem in SSA and provides a baseline against which to compare the effect of any interventions to reduce the alloimmunization risk.

Red Blood Cell Alloimmunization in Multitransfused Pediatric Population in a Tertiary Care Hospital

OBJECTIVES

To estimate the prevalence and specificity pattern of red blood cell (RBC) alloimmunization among pediatric multitransfused patients, and to identify the factors associated with alloimmunization.

METHODS

This was a descriptive cross-sectional study conducted among mutitransfused pediatric patients over a period of two years. The relevant clinical details of patients were collected, and RBC antibody screening was done. Samples with positive antibody screen were subjected to antibody identification. Patient factors were analysed to find any significant relation to the development of RBC alloimmunization.

RESULTS

Alloantibodies were obtained in 4 (6.35%) of the total 63 patients, and autoantibody in 1 (1.59%). The specificities of alloantibodies identified were all against Rh antigens-one each of anti E, anti c, anti Cw and anti D + anti C. A significant association was seen between development of alloimmunization and first transfusion at more than 2 y of age.

CONCLUSIONS

RBC alloimmunization against Rhesus (Rh) antigens is a significant problem for multitransfused children in our population. Extended RBC phenotyping at least for antigens of the Rh system and provision of antigen matched RBCs may be an option for such children, where ongoing transfusion requirement is anticipated.

Transfusion in Haemoglobinopathies: Review and recommendations for local blood banks and transfusion services in Oman

Sickle cell disease and homozygous β-thalassaemia are common haemoglobinopathies in Oman, with many implications for local healthcare services. The transfusions of such patients take place in many hospitals throughout the country. Indications for blood transfusions require local recommendations and guidelines to ensure standardised levels of care. This article summarises existing transfusion guidelines for this group of patients and provides recommendations for blood banks and transfusion services in Oman. This information is especially pertinent to medical professionals and policy-makers developing required services for the standardised transfusion support of these patients.

Clinical and epidemiological profile of alloimmunized and autoimmunized multi-transfused patients against red blood cell antigens in a blood center of Minas Gerais

Background

The large diversity of red blood cell antigens favors, especially in multi-transfused patients, the occurrence of autoimmunization and alloimmunization with the risk of hemolytic transfusion reactions. Thus, this study aimed to determine the rates of alloimmunization and autoimmunization in these individuals, as well as the types of alloantibodies and their systems, clinical and epidemiological aspects and the frequency of autoimmunity in alloimmunized and non-alloimmunized patients.

Methods

In a retrospective study, 153 multi-transfused patients from 2006 to 2014 were evaluated. Sixty-eight had onco-hematological diseases, 64 had hemoglobinopathies and 21 had chronic renal failure. Descriptive analyses were carried out with the proportions being compared using the chi-square test, with the significance level set at 5%.

Results

The Rh system was the most frequently involved (53.11%) and anti-E and anti-K (Kell system) were the most prevalent alloantibodies (21.87% each). Autoantibodies were found in ten patients (6.54%) with the percentages of autoimmunization in alloimmunized and non-alloimmunized individuals being 29.16% and 2.32%, respectively (p = 0.0001). There was a significant difference between autoimmunization and the number of transfusions (16.21% in 6–10 vs. 5.26% <6 vs. 2.56% >10; p = 0.0203) and diseases (19.04% in chronic renal failure vs. 6.25% in hemoglobinopathies vs. 2.94% in onco-hematological diseases; p = 0.0329).

Conclusion

The results show a strong correlation between alloimmunization and autoimmunization. Moreover, they reinforce the need for further studies on the clinical and epidemiological profile of multi-transfused patients in relation to alloimmunity and autoimmunity, especially the latter, for a better understanding of its etiopathogenesis and physiopathogenesis.

Red blood cell minor antigen mismatches during chronic transfusion therapy for sickle cell anemia

BACKGROUND

Red blood cell (RBC) alloimmunization occurs at a high frequency in sickle cell anemia (SCA) despite serologic matching for Rh (C/c, E/e) and K antigens. RBC minor antigen genotyping allows for prediction of antigens and RH variants that may lead to alloimmunization.

STUDY DESIGN AND METHODS

RBC antigen genotyping was performed on chronically transfused pediatric SCA patients, using PreciseType human erythrocyte antigen (HEA), RHCE, and RHD BeadChip arrays. All patients received C/c, E/e, and K serologically matched units (Category 1); patients with prior RBC antibodies were also matched for Fy^a , Jk^b , and any antibodies (Category 2). The RBC genotypes of all leukoreduced (LR) units transfused over a 12-month period were determined by the prototype HEA-LR BeadChip assay.

RESULTS

There were 2320 RBC units transfused to 90 patients in 1135 transfusion episodes. Thirty-five (38.9%) patients had homozygous or compound heterozygous RH variants. Seven new alloantibodies were detected, with alloantibody incidence of 0.706 in 100 units for Category 2 transfusions and 0.068 in 100 units for Category 1 (p = 0.02). Three patients on Category 2 transfusions formed new anti-Js^a and had a higher rate of exposure to Js^a than those who did not form anti-Js^a (20.4 vs. 8.33 exposures/100 units, p = 0.02). The most frequent mismatches were S (43.9%), Do^a (43.9%), Fy^a (29.2%), M (28.4%), and Jk^b (28.1%).

CONCLUSIONS

Alloimmunization incidence was higher in those with prior RBC antibodies, suggesting that past immunologic responders are at higher risk for future alloimmunization and therefore may benefit from more extensive antigen matching beyond C/c, E/e, K, Fy^a , and Jk^b .

Genotyping Applications for Transplantation and Transfusion Management: The Emory Experience

Current genotyping methodologies for transplantation and transfusion management employ multiplex systems that allow for simultaneous detection of multiple HLA antigens, human platelet antigens, and red blood cell (RBC) antigens. The development of high-resolution, molecular HLA typing has led to improved outcomes in unrelated hematopoietic stem cell transplants by better identifying compatible alleles of the HLA-A, B, C, DRB1, and DQB1 antigens. In solid organ transplantation, the combination of high-resolution HLA typing with solid-phase antibody identification has proven of value for highly sensitized patients and has significantly reduced incompatible crossmatches at the time of organ allocation. This database-driven, combined HLA antigen/antibody testing has enabled routine implementation of "virtual crossmatching" and may even obviate the need for physical crossmatching. In addition, DNA-based testing for RBC antigens provides an alternative typing method that mitigates many of the limitations of hemagglutination-based phenotyping. Although RBC genotyping has utility in various transfusion settings, it has arguably been most useful for minimizing alloimmunization in the management of transfusion-dependent patients with sickle cell disease or thalassemia. The availability of high-throughput RBC genotyping for both individuals and large populations of donors, along with coordinated informatics systems to compare patients' antigen profiles with available antigen-negative and/or rare blood-typed donors, holds promise for improving the efficiency, reliability, and extent of RBC matching for this population.

Cross-Cultural Care Training for Pediatric Hematology/Oncology Fellows

INTRODUCTION

Physicians are entrusted with the medical care of culturally and socially diverse patient populations. In addition, pediatric hematologists/oncologists are faced with the challenge of taking care of children with life-threatening and complex conditions. We implemented a cross-cultural care training curriculum for our pediatric hematology/oncology fellows with the goal of preparing them to handle complex clinical situations while navigating different social and cultural belief systems.

METHODS

The curriculum includes a precourse self-reflection; a learning module with a review of published literature; faculty-facilitated small-group role-play simulations; interactive sessions with language interpreters and physicians from different cultural, ethnic, and religious belief systems; and a postcourse reflection.

RESULTS

Fellows who participated in the curriculum strongly agreed that the module was helpful, indicating that it enhanced their communication skills, improved delivery of cross-cultural care, and had a sustained impact on their interaction with medical language interpreters.

DISCUSSION

Cross-cultural care training should be integrated into any pediatric hematology/oncology training curriculum. Sessions directed at addressing the perceived gaps between physician awareness and the patient's belief systems can increase awareness of personal biases in practice and improve interview techniques. Likewise, self-reflection can help physicians apply their medical knowledge and skills in the appropriate cultural and social context, thereby improving patient satisfaction, partnerships, and health care outcomes.

Red blood cell alloimmunization in patients with sickle cell disease: correlation with HLA and cytokine gene polymorphisms

BACKGROUND

The reason for the difference in susceptibility to red blood cell (RBC) alloimmunization among patients with sickle cell disease (SCD) is not clearly understood and is probably the result of multiple factors. Our hypothesis is that genetic polymorphisms are associated with RBC alloimmunization.

STUDY DESIGN AND METHODS

We investigated the possible association of susceptibility to RBC alloimmunization with polymorphisms of HLA and cytokines genes in 161 SCD patients prior exposed to RBC transfusion. Cytokine gene polymorphisms were analyzed by polymerase chain reaction (PCR) and TaqMan assays. HLA Class I genotyping was performed using PCR-specific sequence of oligonucleotides. Polymorphism frequencies were compared using the Fisher's exact test.

RESULTS

Our results revealed increased percentage of the A allele and the GA genotype of the TNFA -308G/A cytokine among alloimmunized patients when compared to nonalloimmunized patients (A allele, 16.4% vs. 6.8%, p = 0.004; GA genotype, 32.8% vs. 11.7%, p = 0.0021). In addition, the IL1B -511T allele and the IL1B -511TT and CT genotype frequencies were overrepresented among alloimmunized patients (T allele, 53.0% vs. 37.5%, p = 0.0085; CT + TT genotypes, 81.82% vs. 60.87%, p = 0.0071). In relation to HLA Class I, we found a higher frequency of HLA-DRB1*15 among patients alloimmunized to Rh antigens when compared to nonalloimmunized patients (15.63% vs. 6.98%, p = 0.044).

CONCLUSION

Brazilian SCD patients with the TNFA, IL1B, and HLA-DRB1 gene polymorphisms were at increased risk of becoming alloimmunized by RBC transfusions. These findings may contribute to the development of future therapeutic strategies for patients with SCD with higher susceptibility of alloimmunization.

Red blood cell alloimmunization in transfused patients with bone marrow failure syndromes

BACKGROUND

Red blood cell (RBC) alloimmunization is a concern for patients who receive multiple or chronic transfusions. Alloimmunization prevalence in transfused patients with bone marrow failure syndrome (BMFS) is unknown. This study aimed to determine physician practice for RBC antigen matching, immunization rates, and antibody specificities in patients with BMFS.

STUDY DESIGN AND METHODS

The clinical records of all patients with BMFS seen at the Children's Hospital of Philadelphia between 2001 and 2015 were reviewed. Immunization rate was determined per 100 units transfused.

RESULTS

ABO/D, C, E, and K (CEK) RBC matching was requested for 21.8% of patients. A total of 3782 RBC units were transfused to 87 patients, of which 2551 (67.5%) were CEK matched and 1231 (32.5%) were ABO/D only matched. The majority of units transfused to patients on a chronic transfusion regimen were CEK matched (89.6% of 2728 units). No anti-C, -E, or -K antibodies formed in any patient during the 14-year study period. Two alloantibodies and two autoantibodies formed, resulting in a rate of 0.05 alloantibodies and 0.05 autoantibodies per 100 units transfused. The prevalence of alloimmunization was 2.3%.

CONCLUSION

The rate and prevalence of RBC alloimmunization were low in patients with BMFS. CEK matching avoided alloimmunization to these antigens in chronically transfused patients.

Incidence of alloimunization in sickle cell disease: experience of a center in São Paulo

OBJECTIVE

To identify the incidence of alloimmunization in sickle cell disease patients, as well as autoantibodies and the phenotypic profile of these patients for the following erythrocyte antigen groups: Rh, Kell, Kidd, Duffy and MNS.

METHODS

fifty-seven patients were evaluated during follow-up at the Anemia Outpatient Clinic of Irmandade da Santa Casa de São Paulo, where a search for irregular antibodies and phenotyping was carried out.

RESULTS

Patients' median alloimmunization age in sickle cell disease was 25 years, and irregular antibodies were found in 22.6% of them. Anti-Kell antibody was the most frequent (7.5%) followed by anti-C (5.7%).

CONCLUSION

The prevalence of alloimmunization and of patients with autoantibodies among individuals with sickle cell disease followed at the Anemia Outpatient Clinic of Irmandade da Santa Casa de Misericórdia de São de Paulo was determined. The risk of alloimmunization was higher in patients who received more than 3 red blood cell units in the past 2 years. The most prevalent alloantibodies were anti-Kell and anti-C.

Predictors of Red Cell Alloimmunization in Kurdish Multi Transfused Patients with Hemoglobinopathies in Iraq

Hemoglobinopathies are significant health problems in Iraq, including its Northern Kurdistan region. One of the essential components of management of these disorders is regular lifelong blood transfusions. The latter is associated with several complications including red cell alloimmunization. No study has looked at the frequency of alloimmunization and its associations in the country. To address the latter issue, 401 multi transfused patients [311 with β-thalassemia (β-thal) syndrome and 90 with sickle cell disease], registered at a large thalassemia care center in Iraqi Kurdistan had their records reviewed, and their sera tested for atypical antibodies using screening and extended red cell panels. Red cell alloimmunization was detected in 18 patients (4.5%) with a total of 20 alloantibodies, while no autoantibodies were detected. The most frequent alloantibody was anti-E, followed by anti-D, anti-K, anti-C(w), anti-C, anti-c and anti-Le(a). Ethnicity was an important predictor of alloimmunization, while age at start of transfusion (>2 vs. ≤2 years) (p = 0.005), Rhesus D (RhD) negative status (p = 0.0017) and history of previous transfusion reactions (p = 0.007) showed a statistically significant higher rate of alloimmunization. However, patients' age, gender, number of units transfused, underlying diagnosis and splenectomy were not significantly associated with alloimmunization. Based on our observations, measures to reduce alloimmunization rates may include extended matching for Rhesus and Kell antigens and early initiation of blood transfusions.

Red blood cell alloimmunization is influenced by recipient inflammatory state at time of transfusion in patients with sickle cell disease

Sickle cell disease (SCD) patients are at increased risk of red blood cell (RBC) alloimmunization. Recipient inflammatory state at time of transfusion has been shown to regulate alloimmunization in murine models, but evidence is lacking in SCD patients. We retrospectively studied a cohort of alloimmunized SCD patients to determine the influence of pro-inflammatory SCD-related complications at time of transfusion on alloimmunization. For each transfusion, the presence of pro-inflammatory state, degree of RBC antigen matching, unit age, storage solution and alloantibody detection date were ascertained. Transfusion-associated pro-inflammatory events were compared between transfusions resulting and not resulting in new alloantibodies. Univariate analysis and multivariate logistic regression were performed. Fifty-two patients received 3166 pre-storage leuco-reduced transfusions of which 128 resulted in alloantibodies. Transfusions during inflammatory events were associated with increased alloantibody risk on univariate and multivariate analysis; acute chest syndrome and vaso-occlusive crisis showed strongest associations with alloimmunization. Increased antigen matching demonstrated a protective effect on alloimmunization (univariate and multivariate analysis). Although an association was seen between citrate-phosphate-dextrose (adenine) stored units and alloimmunization on univariate analysis, no effect was found on multivariate analysis. Identifying recipient pro-inflammatory states at time of transfusion that promote alloimmunization can impact RBC unit selection decisions for SCD patients at risk for alloimmunization.

High multi-cytokine levels are not a predictive marker of alloimmunization in transfused sickle cell disease patients

Patients with sickle cell disease (SCD) receive multiple red blood cell (RBC) transfusions for both prevention of and therapy for disease-related complications. In some patients, transfusion results in development of both allo- and auto-antibodies to RBC antigens. What precipitates the antibody formation is currently unclear. It has been hypothesized that a pro-inflammatory state preceding the therapeutic transfusion may be a predisposing factor. Plasma levels of ten cytokines were evaluated upon recruitment to the study of 83 children with SCD undergoing therapeutic RBC transfusions. The levels of cytokines were correlated with development of anti-RBC antibodies prior, or during seven years post recruitment. Twelve subjects displayed significantly higher levels of all cytokines examined, with pro-, as well as anti-inflammatory properties. Surprisingly, the elevated levels of cytokines were preferentially found in patients without anti-RBC allo- and/or auto-antibodies. Further, presence of high cytokine levels was not predictive of anti-RBC antibody development during the subsequent seven year follow up. These data suggest that the increased concentration of multiple cytokines is not a biomarker of either the presence of or susceptibility to the development of RBC alloimmunization.

Economic evaluation of a hypothetical screening assay for alloimmunization risk among transfused patients with sickle cell disease

BACKGROUND

Prophylactic antigen-matching can reduce alloimmunization rates among chronically transfused patients with sickle cell disease (SCD), but this matching increases costs and may only benefit 30% of patients. We assessed the clinical and financial value of a potential assay for alloimmunization risk that would allow for targeted antigen-matching.

STUDY DESIGN AND METHODS

A Markov-based model evaluated direct medical costs and alloimmunization events over 10 to 20 years among transfused (simple or exchange) patients with SCD. Four matching strategies were evaluated: prospective matching (for all patients), history-based matching (only for patients with prior alloimmunization), perfectly informed matching (assay with 100% sensitivity, 100% specificity), and imperfectly informed matching (reduced accuracy). Under all matching protocols, matching included C, E, K, and any additional alloantibodies present. A hospital perspective was adopted, with costs (2012US$) and events discounted (3%).

RESULTS

Perfectly informed antigen-matching using a $1000 assay is expected to save $82,334 per patient over 10 years, compared to prospective matching. Perfectly informed antigen-matching is more costly than history-based matching, but reduces alloimmunization events by 45.6% over 10 years. Averting each alloimmunization event using this strategy would cost an additional $10,934 per patient. Imperfectly informed antigen-matching using an assay with 75% specificity and 75% sensitivity is less costly than prospective matching, but increases alloimmunization events. Compared to history-based matching, imperfectly informed matching would decrease alloimmunization events by 32.61%, at an additional cost of $147,915 per patient over 10 years. Cost-effectiveness of informed antigen-matching is largely driven by assay specificity.

CONCLUSIONS

A sufficiently specific assay to inform antigen-matching may be cost-effective in reducing alloimmunization among transfused patients with SCD.

High prevalence of red blood cell alloimmunization in sickle cell disease despite transfusion from Rh-matched minority donors

Rh serologic phenotype–matched transfusions from minority donors do not prevent all Rh alloimmunization in patients with SCD. Variant RH genes are common in patients with SCD and contribute to Rh alloimmunization and transfusion reactions.

Cost-effectiveness of prospective red blood cell antigen matching to prevent alloimmunization among sickle cell patients

BACKGROUND

Sickle cell disease is associated with extensive health care utilization; estimated lifetime costs exceed $460,000 per patient. Approximately 30% of chronically transfused sickle cell patients become alloimmunized to red blood cell antigens, but these patients cannot be identified a priori. Prospective antigen matching can prevent alloimmunization, but is costly and may not benefit most patients.

STUDY DESIGN AND METHODS

A Markov-based model was constructed to compare the health and financial implications of four alternative antigen-matching strategies for chronically transfused sickle cell patients. The strategies varied by the group of patients receiving matched blood (all patients prophylactically or only patients with a history of alloimmunization [history-based]), and by the extent of antigen matching (limited to C, E, and K, or extended to 11 antigens). Direct medical costs and alloimmunization events were assessed over 10- and 20-year periods, for a hypothetical cohort of initially transfusion-naive patients and for a dynamic population.

RESULTS

Within a hypothetical cohort of initially transfusion-naive patients, implementing prophylactic limited matching for all chronically transfused patients instead of history-based limited matching is expected to cost an additional $765.56 million over 10 years, but result in 2072 fewer alloimmunization events. Within the same cohort, implementing prospective extensive matching is expected to cost $1.86 billion more than history-based extensive matching, but result in 2424 fewer alloimmunization events. Averting a single alloimmunization event using prospective matching would cost $369,482 to $769,284. Among a dynamic population over 10 years, prospective limited matching is expected to cost $358.34 million more than history-based limited matching.

CONCLUSIONS

While prospective matching for all transfused patients would reduce alloimmunization, this strategy requires considerable expenditure.

Challenges of alloimmunization in patients with haemoglobinopathies

Red blood cell (RBC) transfusions can be life-sustaining in chronic inherited anaemias, such as thalassaemia, and the indications for blood transfusions in patients with sickle cell disease continue to expand. Complications of transfusions, such as allosensitization, can create significant medical challenges in the management of patients with haemoglobinopathies. This review summarizes key findings from the medical literature related to alloimmunization in haemoglobinopathies and examines potential measures to mitigate these risks. Areas where future studies are needed are also addressed.

Frequency of red cell alloimmunization in patients with sickle cell anemia in an Egyptian referral hospital

INTRODUCTION

Sickle cell anemia (SCA) is an important public health issue in Tanta, Egypt. Erythrocyte transfusions may reduce the morbidity of SCA, however, they are associated with numerous risks. Among other risk categories, alloimmunization to red cell antigens may result from transfusions. The objective of this study was to explore the frequency of red cell alloantibodies among SCA patients who received regular transfusions.

MATERIALS AND METHODS

A total of 42 patients with SCA were included in this study. This work planned to study the presence of alloantibodies to different red cell antigens in multi-transfused SCA patients using the ID card micro-typing system. Clinical and laboratory data were collected and analyzed to find out the frequency, pattern and factors influencing red cell alloimmunization secondary to multiple blood transfusion in these patients.

RESULTS

Of a total of 42 SCA patients included in the study, 21.4% of patients developed alloantibodies. The most common alloantibodies were anti-K, anti-E and anti-C. The rate of incidence of these alloantibodies was 7.1%, 4.8% and 4.8%, respectively. There was significant association between alloantibody and the rate of transfused blood. The mean age of patients with and without alloimmunization was 12.0 and 6.2 years.

CONCLUSIONS

Alloimmunization to minor erythrocyte antigens of variable clinical significance is a frequent finding in transfused SCA patients. Regular screening for red cell alloantibodies would provide better management of these patients.

The potential utility of methoxypoly(ethylene glycol)-mediated prevention of rhesus blood group antigen RhD recognition in transfusion medicine

Red blood cell (RBC) transfusions are an important clinical intervention. However, RBC express hundreds of non-ABO antigens making alloimmunization a significant risk. RhD expression is the most immunologically important non-ABO antigen. Availability of RhD(-) blood, often problematic in North America and Europe, is a significant issue in Asia and Africa where RhD(-) blood is uncommon (<0.5% of supply). The immunocamouflage of RhD is readily accomplished by the covalent grafting of methoxypoly(ethylene glycol) [mPEG] to the RBC membrane. To determine if RhD immunocamouflage would inhibit its immunologic recognition, an in vitro RhD-sensitized antigen presentation assay using PBMC and dendritic cells (DC) from RhD-sensitized women was used. The immunological effects of polymer grafting to an immunodominant RhD peptide, purified RhD protein and intact RhD(+) RBC were examined via T cell proliferation and cytokine release assays. At Day 11, PEGylation significantly attenuated T cell proliferation arising from RhD peptide (~80 → 5%), protein (36 → 0.2%) and intact RBC (33 → 1.4%). Cytokine secretion was similarly blunted following PEGylation of the purified protein or intact RBC. These data support the immunomodulatory effects of PEGylation and the potential utility of this technology in transfusion medicine - especially in situations where RhD(-) blood is rare or in short supply.

Risk factors for alloimmunization in patients with sickle cell anemia

OBJECTIVE

To determine erythrocyte phenotyping in blood donors and patients with sickle cell anemia (SS) treated at Hemocentro of Alagoas and describe the frequency and factors associated with erythrocyte alloimmunization.

METHODS

Cross-sectional study with 102 SS patients and 100 blood donors. The following tests were performed: erythrocyte phenotyping, Direct and Indirect antiglobulin test, and detection of irregular antibodies by panel of phenotyped red blood cells. Data were compared by Mann-Whitney, chi-square or Fisher's exact tests. Factors associated with alloimmunization were studied by univariate and multiple logistic regression analysis.

RESULTS

The most frequent antigens found in patients and blood donors were: c, e, M, s, JK(a). Significant differences were observed between the frequency of the phenotype of patients and donors in regard to antigens s, FY(a) and JK(b). Of 79 transfused patients, 10 presented positive Indirect Coombs. Thirteen alloantibodies were found, 7 of the Rh system, 2 of Kell and 4 were not identified. Factors associated with alloimmunization were the period of time between the last transfusion and the date of the test and more than 10 red blood cell transfusions. Patients who received more than 10 transfusions were 16.39 (95% CI: 2.23-120.59) times more likely to be alloimmunized than patients with fewer transfusions.

CONCLUSION

The prevalence of alloimmunization in SS patients was 12.7%, with 70% of antibodies belonging to the Rh and Kell systems. This study shows the importance of performing erythrocyte phenotyping in blood donors and receptors to decrease the risk of alloimmunization.

Prevalence and specificities of red cell alloantibodies among blood recipients in the Malaysian state of Kelantan

BACKGROUND

Red blood cell (RBC) alloantibodies may be formed following exposure to RBC antigens. In most cases, the alloimmunization develops during pregnancy or from previous blood transfusions. The RBC antigens and their alloantibodies vary among different human populations and ethnic groups, and they do have a clinical significance for their adverse immunological reactions.

AIMS

This study aimed at studying the prevalence of RBC alloantibodies at the Blood Transfusion Unit of Hospital Raja Perempuan Zainab II in Kota Bharu, Malaysia.

PATIENTS AND METHODS

A cross-sectional study was performed utilizing data obtained in the years 2007 and 2008. Data of antibody screening tests from 5719 patients were examined.

RESULTS AND DISCUSSION

The overall prevalence of alloimmunization was 65 (1.13%). The majority of these had a single alloantibody (76.9%), whereas the remaining 23.1% had multiple antibodies. The anti-E antibody comprised the most common alloantibody (24.6%) followed by the anti-Lewis (a) antibodies (18.5%) and the anti-M antibody (13.8%). There were more female recipients than males.

CONCLUSIONS

It was concluded that the findings of this work have been comparable with other published works, and that the main factors associated with alloantibody formation were multiple transfusions and pregnancies. The study also emphasizes the necessity for carrying out immunohematology studies prior to every blood transfusion especially in cases that require multiple transfusions for a long period of time such as in thalassemia patients.

Duffy genotyping facilitates transfusion therapy

The Duffy (FY) blood group system is clinically significant in transfusion medicine because FY antibodies are involved in hemolytic transfusion reactions and hemolytic disease of the newborn. The Fy(a) and Fy(b) antigens are encoded by the FY*A and FY*B alleles which are responsible for the Fy(a+b+), Fy(a+b-) and Fy(a-b+) phenotypes. The Fy(a-b-) phenotype is found in individuals homozygous for a silent FY*B allele, named FY*B ( ES ), which is caused by a mutation in the promoter region of FY*B that result in the loss of FY expression in the erythroid linage. The aim of the present study was to evaluate the role of FY DNA typing as a tool in transfusion compatibility testing. We studied 275 white blood donors from the city of Rosario by serological method and allele specific PCRs. We found that the 106 serologically Fy(a+b+) samples all genotyped as FY*A/FY*B (100%). Among the 94 Fy(a+b-) samples, 81 (86.2%) were FY*A/FY*A and 13 (13.8%) were FY*A/FY*B ( ES ) . Of the 75 Fy(a-b+) 67 (89.3%) were FY*B/FY*B and 8 (10.7%) were FY*B/FY*B ( ES ). No Fy(a-b-) samples were encountered. The frequencies of the FY*A, FY*B and FY*B ( ES ) alleles clearly revealed that the genetic pool analyzed is comprised of Caucasian and non-Caucasian alleles. These results showed that there is an important proportion of patients phenotyped as Fy(b-) that can be exposed to Fy(b+) blood units with no risk of alloimmunization when they carry the FY*A/FY*B ( ES ) genotype. Thus, FY genotyping allow increasing the pool of compatible units facilitating transfusion therapy and benefiting patients that require chronic transfusions.

Transfusion medicine in a developing country - alloantibodies to red blood cells in multi-transfused patients in Saudi Arabia

BACKGROUND

Multiple transfusions are frequently complicated by alloimmunization. This retrospective study aims to determine whether alloimmunization could be accounted for by racial differences between donors and recipients.

MATERIALS AND METHODS

The development of alloantibodies were determined in 68 multi-transfused patients (thalassaemia, n=38) and (sickle cell anemia, n=30).

RESULTS

The overall frequency of alloantibody formation in our patients is 22.06%. Thirteen patients received blood from the same ethnic group (Arab) and none developed antibodies, while of 47 patients who received multi-ethnic blood, 10 developed alloantibodies.

CONCLUSIONS

Alloantibodies formation can be reduced by limiting the transfusion of RBC, collected from donors of the same ethnic origin.

Does an alloimmune response to strong immunogenic red blood cell antigens enhance a response to weaker antigens?

BACKGROUND

It has been suggested that an immune response against the high immunogenic D antigen also augments the immune response to less immunogenic red blood cell (RBC) antigens. Based on the high antibody frequency, E and K antigens can also be regarded as strong immunogens. The question is whether the immunization against E and K antigens also enhances the formation of other antibody specificities. This question is in particular relevant for patients who are currently transfused with RH- and/or K-matched RBCs.

STUDY DESIGN AND METHODS

A retrospective multicenter study analyzed FY, JK, and MNS antibodies alone and in combination with anti-E and/or anti-K. Analysis was performed for primary and subsequent antibody responses.

RESULTS

In the cohort analyzed, 5016 patients possessed 5981 antibodies. Antibodies directed to multiple blood group systems were present in 606 of the 779 (78%) patients with multiple antibodies. In 88 of 1270 (6.9%) patients, FY, JK, and/or MNS antibodies appeared simultaneous with anti-E and/or anti-K during a primary antibody response after transfusion. Patients formed antibodies to antigens in the FY, JK, and MNS systems equally often as first antibodies followed by anti-E or anti-K than as second antibodies after anti-E or anti-K were already present. Patients with anti-E and/or anti-K or with antibodies to antigens in the FY, JK, and/or MNS systems equally often formed additional antibodies during a second antibody response.

CONCLUSION

An immune response against allogeneic RBC antigens defines good responders who readily form antibodies against other antigens. No support was found that the response against strong RBC antigens also enhances the formation against weaker antigens.