Frequency of Duffy, Kidd, Lewis, and Rh Blood Group Antigens and Phenotypes Among Donors in the Al-Ahsa Region, Saudi Arabia.

BACKGROUND: In Al-Ahsa, Saudi Arabia, the high consanguinity rates contribute to the prevalence of inherited hemoglobinopathies such as sickle cell disease and thalassemia, which frequently require blood transfusions. These transfusions carry the risk of alloimmunization, necessitating a precise blood component matching to mitigate health risks. Local antigen frequency data is vital for optimizing transfusion practices and enhancing the safety of these medical procedures for the Al-Ahsa population. METHODS: This study investigated the distribution of Duffy, Kidd, Lewis, and Rh blood group antigens in 1,549 individuals from the region; comparing the frequencies with global data. RESULTS: Serological analyses revealed a high prevalence of the Fy(a+b-) and Jk(a+b+) phenotypes in the Duffy and Kidd blood groups, respectively, with Jk(a-b-) being notably scarce. The Lewis blood group exhibited a significant presence of Le(a-b+) and Le(a+b-) phenotypes, whereas Le(a+b+) was less common. In the Rh system, the D antigen was most prevalent, with other antigens following in descending order of frequency. CONCLUSIONS: The study underscores the regional variation in antigen frequencies, emphasizing the need for local blood banks to adapt their screening and matching practices to mitigate the risk of alloimmunization and enhance transfusion safety. These findings are pivotal for refining transfusion strategies and understanding the immunohematology landscape in Al-Ahsa.

Application of RhD Blood Group to Simulate Antibody Identification Test in Immunohematology Education.

BACKGROUND: Immunohematology skill education is an important part of the transfusion medicine professional training. We tried to solve the difficulty of obtaining suitable and sufficient positive samples in the immunohematology education. METHODS: Different identification panels and panel cells were created by RhD-positive red blood cells (RBCs) and RhD-negative RBCs, according to the underlying antibodies. Diluted anti-D reagent was used as simulated plasma for identification. RESULTS: The antibody identification of single antibody with dose-effect and two antibodies present at the same time were successfully simulated. CONCLUSIONS: It is a practical and cheap method for antibody identification training to use RhD blood group, especially when positive samples are short.

Serologic profiling of D variants in donor routine: unveiling the impact on false-negative results and alloimmunization.

The high number of D variants can lead to the unnecessary use of Rh immune globulin, overuse of D- RBC units, and anti-D allommunization. D variant prevalence varies among ethnic groups, and knowledge of the main variants present in a specific population, their behavior in serologic tests, and their impact on clinical practice is crucial to define the best serologic tests for routine use. The present study aimed to explore the serologic profile of D variants and to determine which variants are most associated with false-negative D typing results and alloimmunization. Donor samples were selected in two study periods. During the first period, D typing was performed on a semi-automated instrument in microplates, and weak D tests were conducted in tube or gel tests. In the second period, D typing was carried out using an automated instrument with microplates, and weak D tests were performed in solid phase. Samples from patients typed as D+ with anti-D were also selected. All samples were characterized by molecular testing. A total of 37 RHD variants were identified. Discrepancies and atypical reactivity without anti-D formation were observed in 83.4 percent of the samples, discrepant D typing results between donations were seen in 12.3 percent, and D+ patients with anti-D comprised 4.3 percent. DAR1.2 was the most prevalent variant. Weak D type 38 was responsible for 75 percent of discrepant samples, followed by weak D type 11, predominantly detected by solid phase. Among the D variants related to alloimmunization, DIVa was the most prevalent, which was not recognized by serologic testing; the same was true for DIIIc. The results highlight the importance of selecting tests for donor screening capable of detecting weak D types 38 and 11, especially in populations where these variants are more prevalent. In pre-transfusion testing, it is crucial that D typing reagents demonstrate weak reactivity with DAR variants; having a serologic strategy to recognize DIVa and DIIIc is also valuable.

A patient with anti-f in India identified by extensive immunohematologic workup.

Anti-f is produced by exposure to the compound antigen ce (f) on red blood cells (RBCs), expressed when both c and e are present on the same protein (cis position). Although anti-f was discovered in 1953, there are few cases reported worldwide because the presence of anti-f is often masked by anti-c or anti-e and is not generally found as a single antibody. In the present case, anti-f was identified by using three-cell screening and 11-cell identification panels. The identification of anti-f was further supported by additional testing, including (1) Rh antigen typing; (2) antibody identification panels (enzyme-treated panel [ficin] and an in-house-constructed Rh panel); (3) look-back and phenotyping of donor RBC units, which were responsible for alloimmunization; and (4) molecular testing of the patient's RBCs.

The Variation of RhD Blood Group in Different Periods in a Patient with Systemic Lupus Erythematosus.

BACKGROUND: Autoimmune hemolytic anemia disease often produces a large number of various autoantibodies, and some autoantibodies may be related to Rh blood group. In rare cases, autoantibodies can specifically target Rh antigen, thus interfering with the identification of Rh blood group. METHODS: A case of systemic lupus erythematosus (SLE) with inconsistent RhD blood group identification results in different periods was reported and the reasons were analyzed. RESULTS: Some autoantibodies can completely block D antigen on red blood cells, resulting in no redundant D sites on red blood cells binding to reagent anti D. In addition, the immunity of the body is extremely low, and the expression of red blood cell blood group antigens in part of the body is inhibited, which will cause the weakening of the expression of Rh antigen in red blood cells. Therefore, when testing the RhD blood type of the patient, the reagent anti D does not agglutinate with the patient's red blood cells, and a false negative result of the initial screening appears. Through the RhD negative confirmation test, the patient's blood type is a serologically weak D phenotype. CONCLUSIONS: If the result of serological preliminary screening test is RhD negative or RhD variant, the recipient should be treated as RhD negative, and RhD negative red blood cells should be transfused during blood transfusion. Conditional laboratories can implement RHD genotyping, which is conducive to improving the precise blood transfusion management level of RhD negative blood recipients, saving rare blood resources and improving the treatment efficiency of patients.

Antenatal RHD screening to guide antenatal anti-D immunoprophylaxis in non-immunized D- pregnant women.

In pregnancy, D- pregnant women may be at risk of becoming immunized against D when carrying a D+ fetus, which may eventually lead to hemolytic disease of the fetus and newborn. Administrating antenatal and postnatal anti-D immunoglobulin prophylaxis decreases the risk of immunization substantially. Noninvasive fetal RHD genotyping, based on testing cell-free DNA extracted from maternal plasma, offers a reliable tool to predict the fetal RhD phenotype during pregnancy. Used as a screening program, antenatal RHD screening can guide the administration of antenatal prophylaxis in non-immunized D- pregnant women so that unnecessary prophylaxis is avoided in those women who carry a D- fetus. In Europe, antenatal RHD screening programs have been running since 2009, demonstrating high test accuracies and program feasibility. In this review, an overview is provided of current state-of-the-art antenatal RHD screening, which includes discussions on the rationale for its implementation, methodology, detection strategies, and test performance. The performance of antenatal RHD screening in a routine setting is characterized by high accuracy, with a high diagnostic sensitivity of ≥99.9 percent. The result of using antenatal RHD screening is that 97-99 percent of the women who carry a D- fetus avoid unnecessary prophylaxis. As such, this activity contributes to avoiding unnecessary treatment and saves valuable anti-D immunoglobulin, which has a shortage worldwide. The main challenges for a reliable noninvasive fetal RHD genotyping assay are low cell-free DNA levels, the genetics of the Rh blood group system, and choosing an appropriate detection strategy for an admixed population. In many parts of the world, however, the main challenge is to improve the basic care for D- pregnant women.

Neonatal and Obstetrical Outcomes of Pregnancies Complicated by Alloimmunization.

BACKGROUND AND OBJECTIVES: Despite advances in the prevention of rhesus (Rh)(D) alloimmunization, alloantibodies to Rh(D) and non-Rh(D) red blood cell antigens continue to be detected in ∼4% of US pregnancies and can result in hemolytic disease of the fetus and newborn (HDFN). Recent reports on HDFN lack granularity and are unable to provide antibody-specific outcomes. The objective of this study was to calculate the frequency of alloimmunization in our large hospital system and summarize the outcomes based on antibody specificity, titer, and other clinical factors. METHODS: We identified all births in a 6-year period after a positive red blood cell antibody screen result during pregnancy and summarized their characteristics and outcomes. RESULTS: A total of 707 neonates were born after a positive maternal antibody screen result (3.0/1000 live births). In 31 (4%), the positive screen result was due to rhesus immune globulin alone. Of the 676 neonates exposed to alloantibodies, the direct antibody test (DAT) result was positive, showing antigen-positivity and evidence of HDFN in 37% of those tested. Neonatal disease was most severe with DAT-positive anti-Rh antibodies (c, C, D, e, E). All neonatal red blood cell transfusions (15) and exchange transfusions (6) were due to anti-Rh alloimmunization. No neonates born to mothers with anti-M, anti-S, anti-Duffy, anti-Kidd A, or anti-Lewis required NICU admission for hyperbilirubinemia or transfusion. CONCLUSIONS: Alloimmunization to Rh-group antibodies continues to cause a majority of the severe HDFN cases in our hospital system. In neonates born to alloimmunized mothers, a positive DAT result revealing antigen-positivity is the best predictor of anemia and hyperbilirubinemia.

Transfusion management and hemoglobin-based oxygen carrier treatment in a patient with anti-Rh17 antibody.

BACKGROUND: A 54-year-old Hispanic OPos female with known history of anti-Rh17 antibodies was diagnosed with Philadelphia-Chromosome positive (Ph+) acute lymphoblastic leukemia (ALL). Rh17, also known as Hr0, is a high-frequency antigen composed of several epitopes on the RhCE protein. Anti-Rh17 antibodies can be made by individuals with missing or varied C/c, E/e antigens. Anti-Rh17 antibodies are clinically significant given multiple case reports of hemolytic disease of the fetus and newborn (HDFN). Finding compatible units for patients with anti-Rh17 can be particularly difficult given that only 1 in 100,000 people are Rh17 negative. STUDY DESIGN AND METHODS: Search for compatible units was conducted by the American Rare Donor Program (ARDP) with no leads. After chemotherapy induction and despite erythropoiesis stimulating agent administration, the patient's hemoglobin continued to trend down to a nadir of 2.8 g/dL. Here we report transfusion of incompatible pRBC to this patient with critically symptomatic anemia. HBOC-201 (Hemopure) was obtained and administered under an emergency compassionate/expanded access designation from the Food and Drug Administration (FDA) under an emergency Investigational New Drug (IND) application. RESULTS AND DISCUSSION: Overall difficulties in this case included the challenge of finding compatible units, dilemma of transfusing incompatible units in a patient with severe anemia and obtaining alternatives to blood products. This case report demonstrates the successful use of HBOC-21 in treating life-threatening anemia.

Anti-D immunization after D positive platelet transfusions in D negative recipients: A systematic review and meta-analysis.

BACKGROUND: Anti-D can be formed after D-incompatible platelet transfusions due to contaminating D+ red blood cells. These antibodies are of particular importance in women of childbearing potential, because anti-D is most often involved in severe cases of hemolytic disease of the fetus and newborn. This systematic review determined the frequency of anti-D after D+ platelet transfusions and risk factors for D alloimmunization. STUDY DESIGN AND METHODS: Relevant literature was searched using PubMed, Embase and Web of Science until December 2022. Overall anti-D frequency and risk factors were estimated using a random effects meta-analysis. RESULTS: In 22 studies, a total of 3028 D- patients received a mean of six D+ platelet transfusions. After a mean follow-up of seven months 106 of 2808 eligible patients formed anti-D. The pooled anti-D frequency was 3.3% (95% CI 2.0-5.0%; I2 71%). After including only patients with an undoubtable follow-up of at least 4 weeks, 29 of 1497 patients formed anti-D with a pooled primary anti-D rate of 1.9% (95% CI 0.9-3.2%, I2 44%). Women and patients receiving whole blood derived platelets had two and five times higher anti-D rates compared with men and patients receiving apheresis derived platelets, respectively. DISCUSSION: Anti-D immunization is low after D incompatible platelet transfusions and dependent on recipients' sex and platelet source. We propose anti-D prophylaxis in girls and women, capable of becoming pregnant in the future, that received D+ platelets, regardless of platelet source, to reduce the risk of anti-D induced hemolytic disease of the fetus and newborn.

Receipt of RhD-positive whole blood for life-threatening bleeding in female children: A survey in alloimmunized mothers regarding minimum acceptable survival benefit relative to risk of maternal alloimmunization to anti-D.

BACKGROUND: Low-titer group O whole blood (LTOWB) for treatment of hemorrhagic shock sometimes necessitates transfusion of RhD-positive units due to short supply of RhD-negative LTOWB. Practitioners must choose between using RhD-positive LTOWB when RhD-negative is unavailable against the risk to a female of childbearing potential of becoming RhD-alloimmunized, risking hemolytic disease of the fetus and newborn (HDFN) in future children, or using component therapy with RhD-negative red cells. This survey asked females with a history of red blood cell (RBC) alloimmunization about their risk tolerance of RhD alloimmunization compared to the potential for improved survival following transfusion of RhD-positive blood for an injured RhD negative female child. STUDY DESIGN AND METHODS: A survey was administered to RBC alloimmunized mothers. Respondents were eligible if they were living in the United States with at least one red cell antibody known to cause HDFN and if they had at least one RBC alloimmunized pregnancy. RESULTS: Responses from 107 RBC alloimmmunized females were analyzed. There were 32/107 (30%) with a history of severe HDFN; 12/107 (11%) had a history of fetal or neonatal loss due to HDFN. The median (interquartile range) absolute improvement in survival at which the respondents would accept RhD-positive transfusions for a female child was 4% (1%-14%). This was not different between females with and without a history of severe or fatal HDFN (p = .08 and 0.38, respectively). CONCLUSION: Alloimmunized mothers would accept the risk of D-alloimmunization in a RhD-negative female child for improved survival in cases of life-threatening bleeding.

A cold case of hemolytic disease of the fetus and newborn resolved by genomic sequencing and population studies to define a new antigen in the Rh system.

BACKGROUND: We report an obstetric case involving an RhD-positive woman who had developed a red blood cell (RBC) antibody that was not detected until after delivery of a newborn, who presented with a positive direct antiglobulin test result. Immunohematology studies suggested that the maternal antibody was directed against a low-prevalence antigen on the paternal and newborn RBCs. RESULTS: Comprehensive blood group profiling by targeted exome sequencing revealed a novel nonsynonymous single nucleotide variant (SNV) RHCE c.486C>G (GenBank MZ326705) on the RHCE*Ce allele, for both the father and newborn. A subsequent genomic-based study to profile blood groups in an Indigenous Australian population revealed the same SNV in 2 of 247 individuals. Serology testing showed that the maternal antibody reacted specifically with RBCs from these two individuals. DISCUSSION: The maternal antibody was directed against a novel antigen in the Rh blood group system arising from an RHCE c.486C>G variant on the RHCE*Ce allele linked to RHD*01. The variant predicts a p.Asn162Lys change on the RhCE protein and has been registered as the 56th antigen in the Rh system, ISBT RH 004063. CONCLUSION: This antibody was of clinical significance, resulting in a mild to moderate hemolytic disease of the fetus and newborn (HDFN). In the past, the cause of such HDFN cases may have remained unresolved. Genomic sequencing combined with population studies now assists in resolving such cases. Further population studies have potential to inform the need to design population-specific red cell antibody typing panels for antibody screening in the Australian population.

Rh immune globulin immunoprophylaxis after RhD-positive red cell exposure in RhD-negative patients via transfusion: A survey of practices.

BACKGROUND: Current Association for the Advancement of Blood & Biotherapies (AABB) standards require transfusion services to have a policy on Rh immune globulin (RhIG) immunoprophylaxis for when RhD-negative patients are exposed to RhD-positive red cells. This is a survey of AABB-accredited transfusion services in the United States (US) regarding institutional policies and practices on RhIG immunoprophylaxis after RhD-negative patients receive RhD-positive (i.e., RhD-incompatible) packed red blood cell (pRBC) and platelet transfusions. RESULTS: Approximately half of the respondents (50.4%, 116/230) have policies on RhIG administration after RhD-incompatible pRBC and platelet transfusions, while others had policies for only pRBC (13.5%, 31/230) or only platelet (17.8%, 41/230) transfusions, but not both. In contrast, 18.3% (42/230) report that their institution has no written policies on RhIG immunoprophylaxis after RhD-incompatible transfusions. Most institutions (70.2%, 99/141) do not have policies addressing safety parameters to mitigate the risk of hemolysis associated with the high dose of RhIG required to prevent RhD alloimmunization after RhD-incompatible pRBC transfusions. DISCUSSION: With approximately half of US AABB-accredited institutions report having policies on RhIG immunoprophylaxis after both RhD-incompatible pRBC and platelet transfusions, some institutions may not be in compliance with AABB standards. Further, most with policies on RhIG immunoprophylaxis after RhD-incompatible pRBC transfusion do not have written safeguards to mitigate the risk of hemolysis associated with the high dose of RhIG required. CONCLUSION: This survey underscores the diverse and inadequate institutional policies on RhIG immunoprophylaxis after RhD exposure in Rh-negative patients via transfusion. This observation identifies an opportunity to improve transfusion safety.

Prediction of the antigenic regions in eight RhD variants identified by computational biology.

BACKGROUND AND OBJECTIVES: Changes in RHD generate variations in protein structure that lead to antigenic variants. The classical model divides them into quantitative (weak and Del) and qualitative (partial D). There are two types of protein antigens: linear and conformational. Computational biology analyses the theoretical assembly of tertiary protein structures and allows us to identify the 'topological' differences between isoforms. Our aim was to determine the theoretical antigenic differences between weak RhD variants compared with normal RhD based on structural analysis using bioinformatic techniques. MATERIALS AND METHODS: We analysed the variations in secondary structures and hydrophobicity of RHD*01, RHD*01W.1, W2, W3, RHD*09.03.01, RHD*09.04, RHD*11, RHD*15 and RHD*21. We then modelled the tertiary structure and calculated their probable antigenic regions, intra-protein interactions, displacement and membrane width and compared them with Rhce. RESULTS: The 10 proteins are similar in their secondary structure and hydrophobicity, with the main differences observed in the exofacial coils. We identified six potential antigenic regions: one that is unique to RhD (R3), one that is common to all D (R6), three that are highly variable among RhD isoforms (R1, R2 and R4), one that they share with Rhce (R5) and two that are unique to Rhce (Ra and Rbc). CONCLUSION: The alloimmunization capacity of these subjects could be explained by the variability of the antigen pattern, which is not necessarily recognized or recognized with lower intensity by the commercially available antibodies, and not because they have a lower protein concentration in the membrane.

Guideline No. 448: Prevention of Rh D Alloimmunization.

OBJECTIVE: This guideline provides recommendations for the prevention of Rh D alloimmunization (isoimmunization) in pregnancy, including parental testing, routine postpartum and antepartum prophylaxis, and other clinical indications for prophylaxis. Prevention of red cell alloimmunization in pregnancy with atypical antigens (other than the D antigen), for which immunoprophylaxis is not currently available, is not addressed in this guideline. TARGET POPULATION: All Rh D-negative pregnant individuals at risk for Rh D alloimmunization due to potential exposure to a paternally derived fetal Rh D antigen. OUTCOMES: Routine postpartum and antepartum Rh D immunoprophylaxis reduces the risk of Rh D alloimmunization at 6 months postpartum and in a subsequent pregnancy. BENEFITS, HARMS, AND COSTS: This guideline details the population of pregnant individuals who may benefit from Rho(D) immune globulin (RhIG) immunoprophylaxis. Thus, those for whom the intervention is not required may avoid adverse effects, while those who are at risk of alloimmunization may mitigate this risk for themselves and/or their fetus. EVIDENCE: For recommendations regarding use of RhIG, Medline and Medline in Process via Ovid and Embase Classic + Embase via Ovid were searched using both the trials and observational studies search strategies with study design filters. For trials, the Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Database of Abstracts of Reviews of Effects via Ovid were also searched. All databases were searched from January 2000 to November 26, 2019. Studies published before 2000 were captured from the grey literature of national obstetrics and gynaecology specialty societies, luminary specialty journals, and bibliographic searching. A formal process for the systematic review was undertaken for this update, as described in the systematic review manuscript published separately. VALIDATION METHODS: The authors rated the quality of evidence and strength of recommendations using the SOGC's modified GRADE approach. See Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional [weak] recommendations). INTENDED AUDIENCE: The intended users of this guideline include prenatal care providers such as obstetricians, midwives, family physicians, emergency room physicians, and residents, as well as registered nurses and nurse practitioners. TWEETABLE ABSTRACT: An updated Canadian guideline for prevention of Rh D alloimmunization addresses D variants, cffDNA for fetal Rh type, and updates recommendations on timing of RhIG administration. SUMMARY STATEMENTS: RECOMMENDATIONS.

Society for Maternal-Fetal Medicine Statement: RhD immune globulin after spontaneous or induced abortion at less than 12 weeks of gestation.

Guidelines for the management of first-trimester spontaneous and induced abortion vary in terms of rhesus factor D (RhD) testing and RhD immune globulin (RhIg) administration. These existing guidelines are based on limited data that do not convincingly demonstrate the safety of withholding RhIg for first-trimester abortions or pregnancy losses. Given the adverse fetal and neonatal outcomes associated with RhD alloimmunization, prevention of maternal sensitization is essential in RhD-negative patients who may experience subsequent pregnancies. In care settings in which RhD testing and RhIg administration are logistically and financially feasible and do not hinder access to abortion care, we recommend offering both RhD testing and RhIg administration for spontaneous and induced abortion at <12 weeks of gestation in unsensitized, RhD-negative individuals. Guidelines for RhD testing and RhIg administration in the first trimester must balance the prevention of alloimmunization with the individual- and population-level harms of restricted access to abortion.

Low titer group O whole blood and risk of RhD alloimmunization: Rationale for use in Finland.

BACKGROUND: Prehospital low-titer group O whole blood (LTOWB) used for patients with life-threatening hemorrhage is often RhD positive. The most important complication following RhD alloimmunization is hemolytic disease of the fetus and newborn (HDFN). Preceding clinical use of RhD positive LTOWB, we estimated the risk of HDFN due to LTOWB prehospital transfusion in the Finnish population. STUDY DESIGN AND METHODS: We collected data on prehospital transfusions in Tampere and Helsinki University Hospital areas. Using the mean of reported alloimmunization rates in trauma studies (24%) and a higher reported rate representing trauma patients of 13-50 years old (42.7%), we estimated the risk of HDFN and extrapolated it to the whole of Finland. RESULTS: We estimated that in Finland, with the current prehospital transfusion rate we would see 1-3 cases of severe HDFN due to prehospital LTOWB transfusions every 10 years, and fetal death due to HDFN caused by LTOWB transfusion less than once in 100 years. DISCUSSION: The estimated risk of serious HDFN due to prehospital LTOWB transfusion in the Finnish population is similar to previous estimates. As Finland routinely screens expectant mothers for red blood cell antibodies and as the contemporary treatment of HDFN is very effective, we support the prehospital use of RhD positive LTOWB in all patient groups.

Cases of RhD variants RhD*DAU2/DAU6 and RhD*weak D type 4.1 in pregnant women in Saudi Arabia.

The D antigen is one of the most immunogenic and clinically significant antigens of the Rh blood group system due to its various genotypes that encode for more than 450 different variants. Accurate RhD typing and D variant identification is crucial specially in prenatal screening during pregnancy. Women with RhD -ve phenotype are eligible to Rh immune globulin (RhIG) prophylaxis for the prevention of anti-D alloimmunization and hemolytic disease of the fetus and newborn (HDFN). However, there are some women who possess RhD variant alleles, who are mistakenly grouped as RhD positive and considered not eligible for RhIG prophylaxis, putting them at risk of anti-D alloimmunization and consequently leading to HDFN during subsequent pregnancies. Here, we describe  two cases of RhD variants DAU2/DAU6 and Weak D type 4.1 in obstetric patients who were grouped as RhD +ve with negative antibody screening during routine serologic  testing. Weak/Partial D molecular analysis using genomic DNA Red Cell Genotyping (RCG) revealed that both patients had RhD variants, one of which DAU2/DAU6 allele associated with anti-D alloimmunization. According to routine testing neither patients received RhIG or transfusion. In this case report we document to our knowledge the first reported cases of RhD variants among pregnant women in Saudi Arabia.

The effect of extended c, E and K matching in females under 45 years of age on the incidence of transfusion-induced red blood cell alloimmunisation.

Maternal alloantibodies directed against fetal red blood cell (RBC) antigens may cause potentially life-threatening haemolytic disease of the fetus and newborn (HDFN). Dutch transfusion guidelines therefore prescribe preventive cEK matching for all (pre-)fertile females. To quantify the impact of cEK matching, we compared overall and antigen-specific cumulative RBC alloimmunisation incidences in females and males aged <45 years. Among a multicentre cohort comprised of patients who received their first and subsequent RBC unit between 2005 and 2019, first-formed RBC alloantibodies were detected in 47 of 2998 (1·6%) females and 49 of 2507 (2·0%) males. Comparing females and males, overall alloimmunisation incidences were comparable (3·1% [95% confidence interval (CI) 2·1-4·4] versus 3·5% (95% CI 2·4-4·9, P = 0·853) after 10 units transfused). However, cEK alloimmunisation incidences were significantly lower among females (0·6% (95% CI 0·3-1.5) versus 2·2% (95% CI 1·5-3·4, P = 0·001) after 10 units transfused). Yet, despite cEK-matching guidelines being in effect, 6·5%, 3·6% and 0·2% of all RBC units remained mismatched for c, E or K antigens respectively. Most of these mismatches were almost always due to emergency settings. Even though cEK alloimmunisation was not prevented completely, implementation of cEK matching resulted in an alloantigen-exposure risk reduction of up to 98%.

Anti-D alloimmunization in Rh(D) negative adults with severe traumatic injury.

INTRODUCTION: Widely varying rates of alloimmunization associated with transfusing uncrossmatched RBC products to trauma patients as part of hemostatic resuscitation have been reported. We characterized the rates of RBC alloimmunization in our severely injured Rh(D) negative trauma population who received uncrossmatched Rh(D) positive RBC products. METHODS: In a 10-year retrospective analysis to assess Rh(D) alloimmunization risks, Rh(D) negative adult trauma patients initially requiring uncrossmatched group O Rh(D) positive RBC products with either RBC units or low titer group O whole blood as part of massive transfusion protocol (MTP) activation were identified. Only those Rh(D) negative patients whose initial antibody screenings were negative were included. Duration of serologic follow-up from date of MTP activation to either date of anti-D detection or most recent negative antibody screening was calculated. RESULTS: There were 129 eligible Rh(D) negative trauma patients identified. Median injury severity score was 25. Anti-D was detected in 10 (7.8%) patients after a median of 161.5 days; the median duration of serologic follow-up in those who did not have anti-D detected was 220 days. Patients who had anti-D detected were less severely injured and received fewer Rh(D) positive RBC products versus those who did not. DISCUSSION: In our severely injured adult trauma patients with MTP activation requiring uncrossmatched group O Rh(D) positive RBC products, the rate of anti-D detection was low. Additional studies are necessary to determine generalizability of these findings and fully characterize alloimmunization risks in trauma patients with varying extents of injury.

Rate of RhD-alloimmunization after the transfusion of multiple RhD-positive primary red blood cell-containing products.

INTRODUCTION: Early transfusion reduces mortality in bleeding patients. In this setting, RhD-positive blood products might be transfused. This study determined the association between the RhD-alloimmunization rate and the number of RhD-positive products transfused. METHODS: RhD-negative patients between 13 and 50 years who were transfused with ≥1 RhD-positive red blood cell (RBC) or whole blood units between January 1, 2000 and December 31, 2019 in a healthcare network were identified. Study patients had to have had at least one antibody detection test performed ≥14 days after the index RhD-positive transfusion and not receive RhIg. Patients were stratified into groups that received 1, 2, 3-5, 6-10, 11-20, and >20 RhD-positive transfusions and the RhD-alloimmunization rate was determined for each group. RESULTS: There were 335 patients included; 52/335 (15.5%) were females. Overall, there were 117/335 (34.9%, CI: 29.8%-40.3%) recipients who became RhD-alloimmunized. There was no significant dosage effect in the RhD-alloimmunization rates as the exposure to RhD-positive units increased from one RhD-positive unit to more than 20 RhD-positive units (p = .270 for non-parametric trend test). In an exploratory analysis, patients who received 100% of their RhD-positive transfusions within 72 h of the index transfusion had a significantly higher rate of RhD-alloimmunization compared to those who were transfused over a longer period of time (42.3% vs. 21.4%, respectively; p = .001). CONCLUSION: These results suggest that there may not be an increased RhD-alloimmunization risk with transfusing multiple RhD-positive units after one RhD-positive unit has been transfused. These findings need confirmation in larger studies.