Standard Compared With Extended Red Blood Cell Antigen Matching for Prevention of Subsequent Hemolytic Disease of the Fetus and Newborn: A Systematic Review

OBJECTIVE

To systematically review and meta-analyze alloimmunization among recipients of red blood cells (RBCs) matched for ABO blood type and Rhesus D (ABO+D) antigen compared with those also matched for c, E, and Kell (cEK).

DATA SOURCES

Four online databases (Medline, Scopus, EMBASE, ClinicalTrials.gov) were searched from March 28, 2023, to April 1, 2024. The search protocol was peer reviewed and published on PROSPERO (CRD42023411620).

METHODS OF STUDY SELECTION

Studies reporting alloimmunization as the primary outcome among recipients of RBCs matched for ABO+D or additional cEK matching were included. Patients transfused with unmatched RBCs or a mixture of matching regimens were excluded. Risk of bias was assessed with Cochrane Tool to Assess Risk of Bias in Cohort Studies and Tool for Risk of Bias. Random-effects meta-analysis was used to combine effect estimates.

TABULATION, INTEGRATION, AND RESULTS

Ten studies met criteria. Risk of bias was low. Overall, 91,221 patients were transfused, of whom 40,220 (44.1%) received additional cEK-matched RBCs. The overall rate of alloimmunization was 6.2% (95% CI, 2.5-14.9%) for ABO+D-only matching and 1.9% (95% CI, 0.7-5.1%) when cEK was added. Time of follow-up antibody testing ranged from 6 to 18 months after transfusion. Additional cEK match was associated with significantly less alloimmunization compared with standard ABO+D match (odds ratio [OR] 0.37, 95% CI, 0.20-0.69). This association remained when chronically transfused patients were excluded (OR 0.65, 95% CI, 0.54-0.79) and for alloimmunization to c, E, or K antigens only (OR 0.29, 95% CI, 0.18-0.47).

CONCLUSION

Additional cEK RBC matching protocols were associated with lower odds of recipient alloimmunization. Given severe sequelae of alloimmunization in pregnancy, routine cEK matching for transfusion in people with pregnancy potential younger than age 50 years in the United States merits consideration.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42023411620.

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.

Haemolytic transfusion reactions caused by non-ABO red cell antibodies reported to the Norwegian Haemovigilance System 2004-2020

BACKGROUND AND OBJECTIVES

The aim of this study was to analyse the reports received in the Norwegian Haemovigilance System from 2004 to 2020 on acute and delayed haemolytic transfusion reactions caused by non-ABO red cell antibodies.

MATERIALS AND METHODS

Antibody specificity, clinical symptoms and outcomes were included when available.

RESULTS

After transfusion of 3.7 million red cell concentrates, reports on 78 cases of haemolytic transfusion reactions caused by non-ABO red cell antibodies were received, corresponding to an incidence of 1 in 47,000 transfused red cell concentrates. There were 30 acute and 48 delayed haemolytic transfusion reactions. A total of 113 red cell antibodies were found: 82 alloantibodies, 6 autoantibodies and 25 cases where the antibody specificity could not be determined. Two fatalities occurred: one caused by anti-Wra and one caused by an unidentified red cell antibody. The most frequently reported antibody specificities were those in the Rh and Kidd blood group systems, representing 24% and 14%, respectively, of all the antibodies identified. In six cases, errors occurred, leading to the issuing of blood units without the required phenotype match.

CONCLUSIONS

Despite the possible underreporting, the low number of serious haemolytic transfusion reactions reflects an adequate pre-transfusion practice by the Norwegian blood banks.

Extensive red blood cell matching considering patient alloimmunization risk

BACKGROUND AND OBJECTIVES

Red blood cell (RBC) transfusions pose a risk of alloantibody development in patients. For patients with increased alloimmunization risk, extended preventive matching is advised, encompassing not only the ABO-D blood groups but also the most clinically relevant minor antigens: C, c, E, e, K, Fya, Fyb, Jka, Jkb, S and s. This study incorporates patient-specific data and the clinical consequences of mismatching into the allocation process.

MATERIALS AND METHODS

We have redefined the MINimize Relative Alloimmunization Risks (MINRAR) model to include patient group preferences in selecting RBC units from a finite supply. A linear optimization approach was employed, considering both antigen immunogenicity and the clinical impact of mismatches for specific patient groups. We also explore the advantages of informing the blood bank about scheduled transfusions, allowing for a more strategic blood distribution. The model is evaluated using historical data from two Dutch hospitals, measuring shortages and minor antigen mismatches.

RESULTS

The updated model, emphasizing patient group-specific considerations, achieves a similar number of mismatches as the original, yet shifts mismatches among patient groups and antigens, reducing expected alloimmunization consequences. Simultaneous matching for multiple hospitals at the distribution centre level, considering scheduled demands, led to a 30% decrease in mismatches and a 92% reduction in shortages.

CONCLUSION

The reduction of expected alloimmunization consequences by incorporating patient group preferences demonstrates our strategy's effectiveness for patient health. Substantial reductions in mismatches and shortages with multi-hospital collaboration highlights the importance of sharing information in the blood supply chain.

A machine-learning method for biobank-scale genetic prediction of blood group antigens

A key element for successful blood transfusion is compatibility of the patient and donor red blood cell (RBC) antigens. Precise antigen matching reduces the risk for immunization and other adverse transfusion outcomes. RBC antigens are encoded by specific genes, which allows developing computational methods for determining antigens from genomic data. We describe here a classification method for determining RBC antigens from genotyping array data. Random forest models for 39 RBC antigens in 14 blood group systems and for human platelet antigen (HPA)-1 were trained and tested using genotype and RBC antigen and HPA-1 typing data available for 1,192 blood donors in the Finnish Blood Service Biobank. The algorithm and models were further evaluated using a validation cohort of 111,667 Danish blood donors. In the Finnish test data set, the median (interquartile range [IQR]) balanced accuracy for 39 models was 99.9 (98.9-100)%. We were able to replicate 34 out of 39 Finnish models in the Danish cohort and the median (IQR) balanced accuracy for classifications was 97.1 (90.1-99.4)%. When applying models trained with the Danish cohort, the median (IQR) balanced accuracy for the 40 Danish models in the Danish test data set was 99.3 (95.1-99.8)%. The RBC antigen and HPA-1 prediction models demonstrated high overall accuracies suitable for probabilistic determination of blood groups and HPA-1 at biobank-scale. Furthermore, population-specific training cohort increased the accuracies of the models. This stand-alone and freely available method is applicable for research and screening for antigen-negative blood donors.

Rethinking the transfusion pathway in myelodysplastic syndromes: Study protocol for a novel randomized feasibility n-of-1 trial of weekly-interval red cell transfusion in myelodysplastic syndromes

BACKGROUND

Anemia in myelodysplastic syndromes (MDS) is associated with poorer health-related quality of life (HRQoL) and physical function, and is frequently treated with transfusions. The current common practice of transfusing multiple red blood cells (RBC) units every 2-4 weeks may result in peaks/troughs in hemoglobin (Hb) level, yet maintaining a stable Hb may better improve HRQoL. We describe a study protocol aiming to investigate the feasibility of weekly low-dose RBC transfusion in MDS patients, including assessing HRQoL and physical function outcomes.

STUDY DESIGN AND METHODS

In this n-of-1 pilot study, patients receive two treatment arms, with randomly allocated treatment sequence: arm A (patient's usual transfusion schedule) and arm B (weekly transfusion, individualized per patient). To facilitate timely delivery of weekly transfusion, extended-matched RBCs are provided, with transfusion based upon the previous week's Hb/pre-transfusion testing results to eliminate delays of awaiting contemporaneous cross-matching. Primary outcome is the feasibility of delivering weekly transfusion. Secondary outcomes include HRQoL, functional activity measurements, RBC usage, and alloimmunization rates. A qualitative substudy explores patient and staff experiences.

RESULTS

The trial is open in Australia, Netherlands, and UK. The first patient was recruited in 2020. Inter-country differences in providing RBCs are observed, including patient genotyping versus serological phenotyping to select compatible units.

DISCUSSION

This pilot trial evaluates a novel personalized transfusion approach of weekly matched RBC transfusion and challenges the dogma of current routine pre-transfusion matching practice. Findings on study feasibility, HRQoL, and physical functional outcomes and the qualitative substudy will inform the design of a larger definitive trial powered for clinical outcomes.

Validation of a flow-cytometry-based red blood cell antigen phenotyping method

BACKGROUND AND OBJECTIVES

Current manual and automated phenotyping methods are based on visual detection of the antigen-antibody interaction. This approach has several limitations including the use of large volumes of patient and reagent red blood cells (RBCs) and antisera to produce a visually detectable reaction. We sought to determine whether the flow cytometry could be developed and validated to perform RBC phenotyping to enable a high-throughput method of phenotyping using comparatively miniscule reagent volumes via fluorescence-based detection of antibody binding.

MATERIALS AND METHODS

RBC phenotyping by flow cytometry was performed using monoclonal direct typing antisera (human IgM): anti-C, -E, -c, -e, -K, -Jk^a , -Jk^b and indirect typing antisera (human IgG): anti-k, -Fy^a , -Fy^b , -S, -s that are commercially available and currently utilized in our blood transfusion services (BTS) for agglutination-based phenotyping assays.

RESULTS

Seventy samples were tested using both flow-cytometry-based-phenotyping and a manual tube standard agglutination assay. For all the antigens tested, 100% concordance was achieved. The flow-cytometry-based method used minimal reagent volume (0.5-1 μl per antigen) compared with the volumes required for manual tube standard agglutination (50 μl per antigen) CONCLUSION: This study demonstrates the successful validation of flow-cytometry-based RBC phenotyping. Flow cytometry offers many benefits compared to common conventional RBC phenotyping methods including high degrees of automation, quantitative assessment with automated interpretation of results and extremely low volumes of reagents. This method could be used for high-throughput, low-cost phenotyping for both blood suppliers and hospital BTS.

An overview of red blood cell and platelet alloimmunisation in transfusion

Post-transfusion alloimmunisation is the main complication of all those observed after one or more transfusion episodes. Alloimmunisation is observed after the transfusion of red blood cell concentrates but also of platelet concentrates. Besides alloimmunisation due to antigens carried almost exclusively by red blood cells such as those of the Rhesus-Kell system, alloimmunisation often raises against HLA antigens; the main responsibility for that, apart from platelet transfusions, lies with residual leukocytes in the products transfused, hence the central importance of effective leukoreduction right from the blood product preparation stage. Alloimmunization is not restricted to transfusion, but it is also observed during pregnancies, carrying out microtransfusions of blood from the fetus immunizing the mother through the placenta (in a retrograde way). Preexisting maternal-fetal immunization can complicate a transfusion program and intensify the creation of alloantibodies in several blood and tissue group systems. The occurrence of autoantibodies, created by several pathogenic reasons, can also interfere with the propensity of certain recipients of blood components to produce alloantibodies. The genetic condition of individuals is in fact strongly linked to the ability or not to recognize antigenic variants foreign to their own biological program and mount an alloimmune response. Some hemoglobin diseases, in carriers of which transfusions can be iterative and lifelong, are complicated by frequent alloimmunizations and amplification of the complications of these alloimmunizations, imposing even stricter transfusion rules. This review details the mechanisms favoring the occurrence of alloimmunization and the immunological principles for the production of molecular and cellular tools for alloimmunization. It concludes with the main preventive measures available to limit the occurrence of these frequent complications of varying severity but sometimes severe.

Measurement of post-transfusion red blood cell survival kinetics in sickle cell disease and β-Thalassemia: A biotin label approach

BACKGROUND

Red blood cell (RBC) transfusions are an important treatment modality for patients with sickle cell disease (SCD) and β-thalassemia. A subgroup of these patients relies on a chronic RBC transfusion regimen. Little is known about RBC survival (RCS) of the transfused allogeneic RBCs. In this study, we aimed to study the RCS kinetics of transfused RBCs in SCD and β-thalassemia and to investigate factors that determine RCS.

METHODS AND MATERIALS

We performed a prospective cohort study on fourteen adults with SCD and β-thalassemia disease receiving a chronic transfusion regimen. RCS and the influence of donor and patient characteristics on RCS were assessed by simultaneous transfusion of two allogeneic RBCs using RBC biotinylation. Phenotyping of well-known RBC markers over time was performed using flow cytometry.

RESULTS

RCS of the two transfused RBC units was similar in most patients. Although intra-individual variation was small, inter-individual variation in RCS kinetics was observed. Most patients demonstrated a non-linear trend in RCS that was different from the observed linear RCS kinetics in healthy volunteers. After an initial slight increase in the proportion of biotinylated RBCs during the first 24 h, a rapid decrease within the first 10-12 days was followed by a slower clearance rate.

CONCLUSION

These are the first data to demonstrate that patient-related factors largely determine post-transfusion RCS behavior of donor RBC in SCD and β-thalassemia, while donor factors exert a negligible effect. Further assessment and modeling of RCS kinetics and its determinants in SCD and β-thalassemia patients may ultimately improve transfusion therapy.

Extended red blood cell matching for all transfusion recipients is feasible

OBJECTIVE

To demonstrate the feasibility and effectiveness of extended matching of red blood cells (RBC) in practice.

BACKGROUND

At present, alloimmunisation preventing matching strategies are only applied for specific transfusion recipient groups and include a limited number of RBC antigens. The general assumption is that providing fully matched RBC units to all transfusion recipients is not feasible. In this article we refute this assumption and compute the proportion of alloimmunisation that can be prevented, when all donors and transfusion recipients are typed for A, B, D plus twelve minor blood group antigens (C, c, E, e, K, Fy^a , Fy^b , Jk^a , Jk^b , M, S and s).

METHODS

We developed a mathematical model that determines the optimal sequence for antigen matching. The model allows for various matching strategies, issuing policies and inventory sizes.

RESULTS

For a dynamic inventory composition (accounting for randomness in the phenotypes supplied and requested) and an antigen identical issuing policy 97% and 94% of alloimmunisation events can be prevented, when respectively one and two RBC units per recipient are requested from an inventory of 1000 units. Although this proportion decreases with smaller inventory sizes, even for an inventory of 60 units almost 50% of all alloimmunisation events can be prevented.

CONCLUSION

In case antigen of both donors and recipients are comprehensively typed, extended preventive matching is feasible for all transfusion recipients in practice and will significantly reduce transfusion-induced alloimmunisation and (alloantibody-induced) haemolytic transfusion reactions.

Is it reasonable for the use of Rh-ee blood? A hospital-based survey from a southern medical center in Taiwan

Identification of alloantibodies and achieving a reduction in the rate of red blood cell (RBC) alloimmunization are important issues to prevent transfusion complications. The aim of this study was to identify the antigen and alloantibodies in our patients and to study the association of alloimmunization with previous transfusion. Transfusion records from the blood bank of Kaohsiung Medical University Hospital between 2015 and 2017 were retrospectively enrolled in the study. Antigen and antibody identification was performed using routine blood bank methods. In total, 56,422 transfusion records from 2015 to 2017 were included in the study. Among them, 1858 alloantibody episodes were found in the pre-transfusion survey, and anti-Mia, anti-E, and cold antibodies were the most common alloantibodies, with a prevalence of 3.29% (1858/56,422). Among them, 130 episodes involved newly found alloantibodies with no alloantibodies found in the previous transfusion survey. Tracing back to these newly transfusion-induced alloantibodies, the antibody was found with a mean of 10.8 ± 7.8 units of packed RBC transfusion, a mean of 66.3 ± 52.8 days, and with a mean of 4.3 ± 2.7 times of transfusion from the first transfusion therapy. An antibody survey revealed that Rh-ee (62.1%) was the most common phenotype in these newly identified antibodies. In summary, this hospital-based study revealed that RBC alloantibody rates were present at rates of 3.29%, with anti-Mia, anti-E, and cold antibodies being the most common alloantibodies. Among them, anti-E was the most commonly developed alloantibody. Given that the Rh-ee group is the most common phenotype in our population, the strategy of using Rh-ee blood for Rh-ee recipients is reasonable for transfusion safety.

Alloimmunization in transfused patients with constitutional anemias in Norway

BACKGROUND AND OBJECTIVES

The status of red blood cell alloimmunization in patients with constitutional anemias including hemoglobinopathies is not known in Norway. The study objective was to investigate the impact of a strategy based on phenotype-matching for C, c, E, e, K, Jka, Jkb, Fya, Fyb, S and s on alloimmunization.

MATERIALS AND METHODS

We reviewed transfusions of 40 patients retrospectively using the computerized blood bank management system and medical records; including diagnosis, age at start of transfusion therapy, gender, number and age of packed red blood cell units transfused, follow-up time, phenotypes of the donors and patients, antigen-negative patients exposed to antigen-positive packed red blood cell units, transfusion reactions and alloantibody specificities.

RESULTS

Forty patients received 5402 packed red blood cell units. Alloimmunization frequency was 20 % for the whole group, being 7%, 25 % and 30 % in patients with sickle cell disease (n = 14), thalassemia (n = 16) and other conditions (n = 10), respectively. The alloantibodies detected were anti-E, -c, -C, -Cw, -K, -Jka and -Lua.

CONCLUSION

Good communication between the clinicians and the transfusion services is essential for successful management of patients with constitutional anemias. Providing full phenotype-matched units was not always possible. Extended pheno-/genotyping before the first transfusion and providing antigen-negative units for antigen-negative patients for at least C, c, E and K in every red cell transfusion would probably have reduced the alloimmunization rate. Non-phenotype-matched transfusions seem to be the main reason for alloimmunization. Finding markers for identifying responders prone to alloimmunization will ensure targeted transfusion strategies.

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.

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%.

The efficacy of ethnic specific blood groups genotyping for routine donor investigation and rare donor identification in Taiwan

BACKGROUND

Large-scale single nucleotide variation (SNV)-based blood group genotyping assays have been made available for over a decade. Due to differences in ethnic groups, there is much diversity in clinically important blood group antigens and genetic variants. Here, we developed a robust matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)-based blood group genotyping method on MassARRAY system.

STUDY DESIGN AND METHODS

A total of 1428 donors were enrolled into three groups: (a) reagent red cell donors; (b) rare donor or common antigen-negative donors; and (c) group O, R₁ R₁ /R₂ R₂ donors. Forty-two SNVs were designed for determining nine blood groups, with X/Y chromosome in two multiplex reactions, on MassARRAY 96-well format system. Further targeted sequence analyses were performed by Sanger sequencing.

RESULTS

WHO reference reagent (NIBSC code: 11/214) was tested for concordance with the provided genotype results. Among the donors, concordance rate was over 99%. Alleles of important phenotypes such as Mi(a+), Di(a+), and Asian-type DEL and alleles of rare blood groups such as Fy(a-), Jk(a-b-) and s- were screened. Three types of discrepancies were found. Serologically, the 'N' antigen was expressed on genetically MM with GYP*Mur red blood cells and caused genuine discrepancies (9.5%). Genetically, allele dropout (ADO) was caused by rare SNV in the primer for Ss genotype (2.1%) and partial insertion of RHD genes (0.9%) led to difficulties in predicting phenotypes.

CONCLUSION

Hemo panel module and MassARRAY System in 96-well format showed good performance in terms of large-scale blood group genotyping and phenotype predictions. Implementation of this method is effective for routine blood group genotype screening of donors.

Understanding the demand for phenotyped red blood cell units and requests to perform molecular red blood cell typing for Australian patients

BACKGROUND

Australian Red Cross Lifeblood has seen a 50 % increase in demand for phenotyped red blood cell (RBC) units between 2016-2018 and a 30 % increase in demand in 2018 to perform molecular RBC typing on patient samples. Lifeblood conducted a survey to understand transfusion laboratory practices for requesting patient phenotyping and/or molecular RBC typing and for selecting phenotyped RBC units in various patient groups.

STUDY DESIGN AND METHODS

An electronic Qualtrics survey form was sent to 296 transfusion laboratories with questions designed to understand the practice of selecting phenotyped RBC units and reasons for requesting extended serology or molecular RBC typing.

RESULTS

49 (16.6 %) transfusion laboratories provided data. Reasons to request extended phenotyping and/or molecular RBC typing for patients included; chronic transfusion (n = 31 laboratories), sickle cell disease (n = 25), Thalassemia (n = 23), requirement for anti-CD38 or other MAB therapy (n = 23) or Myelodysplasia (n = 22). Forty-seven transfusion laboratories provided responses with reasons for requesting molecular RBC typing which included: predicting phenotype in patients with multiple antibodies (n = 31), prior to administering anti-CD38 or other MAB therapies (n = 29), for pregnancy related transfusions (n = 28) or for confirming the phenotype of recently transfused patients (n = 18).

CONCLUSION

Transfusion laboratory practices indicated that phenotyped RBC units were selected for patients requiring chronic transfusion support and/or undergoing MAB therapy. Requests for molecular RBC typing occurred for more complex patient requirements where serological investigations were not suitable or possible due to reagent restrictions.

The Necessity of Clinical Rh Phenotypic Serological Detection and Homotypic Infusion in Patients with Repeated Blood Transfusion

Background

This study analyzed the distribution of Rh serological phenotype in people living in Hangzhou, China, and assessed the necessity of its routine clinical detection and homotypic infusion.

Material/Methods

Blood donors and patients who might need blood transfusion were enrolled into the study, and ABO and 5 major Rh serological antigens (C, c, D, E, and e) were routinely detected. The consistent ABO and Rh serological phenotype blood was transfused between the blood donors and recipients. Irregular antibodies were screened and identified in patients before the blood transfusion. Then, the transfusion adverse effects were monitored and compared with the previous data in the hospital.

Results

The phenotypic frequencies of Rh blood groups were D>C>E>c>e. The CCDee was the most common phenotype and CcdEe was the least common. The detection rate of unexpected antibodies gradually increased, while the unexpected antibodies slowly decreased in the Rh system. There was a correlation between the isotypic infusion of 5 Rh antigens and the detection rate of antibodies in the Rh system (R=0.845). The adverse effects of blood transfusion declined from 19.95% in 2011 with just homotypic ABO infusion to 3.098% in 2019 with the transfusion of homotypic ABO and the 5 major Rh serological antigens.

Conclusions

The consistency of the transfusion with ABO and 5 significant Rh serological antigens could prevent and decrease the high frequency production of isoantibodies, which is of vital importance in reducing the incidence rate of adverse effects in patients receiving transfusions.

Red-blood-cell alloimmunization and prophylactic antigen matching for transfusion in patients with warm autoantibodies

BACKGROUND

Warm autoantibodies (WAA) are antibodies that react with an antigen on a patient's own red-blood-cells and can complicate compatibility testing whether or not they cause clinical haemolysis. The goal of this study was to understand the overall prevalence of WAA, the risk of RBC alloimmunization and determine whether RBC selection practices have an impact on alloimmunization.

MATERIALS AND METHODS

Records of patients (>1 year of age) with an indirect antibody detection test (IAT) and serologic evidence of WAA over a 10-year-period were included. Eight centres from 5 countries collectively reviewed 1 122 245 patients who had an IAT.

RESULTS

Of patients having IAT, 1214 had WAA (0·17%). Transfusion information for 1002 of the patients was available; 631 were transfused after identification of the WAA (63%); of the transfused patients, 390 received prophylactic antigen-matched (PAM) RBCs and 241 did not. Of the 372 patients with WAA who were transfused and had serologic testing 30+ days following transfusion (30-2765 days), 56 developed new RBC alloimmunization (15·1%). Patients who were transfused using a PAM strategy were not protected from new RBC alloimmunization [14·6% (31 of 212 patients) having PAM transfusion approach compared with those not receiving PAM approach (15·6%, 25 of 160 patients, P = 0·8837)].

CONCLUSIONS

The prevalence of WAA in patients having an IAT is low (<1%). A significant portion of patients with WAA form new RBC alloimmunization (15·1%); however, the use of PAM approach for RBC selection was not found to be protective against new alloimmunization.

The contribution of iron deficiency to the risk of peripartum transfusion: a retrospective case control study

Background

Iron deficiency in pregnancy is associated with inferior maternal and fetal outcomes. Postpartum depression, prematurity, intrauterine growth restriction, impaired childhood cognition and transfusion are all sequelae of maternal iron deficiency anemia. Transfusion to women of childbearing age has important consequences including increasing the risk of hemolytic disease of the fetus and newborn with future pregnancies. The relative contribution of iron deficiency to transfusion rates in the peripartum period is unknown. This study aimed to identify the prevalence of iron deficiency and anemia in pregnant women that received peripartum transfusions relative to age-matched non-transfused controls.

Methods

We performed a retrospective case-control study of all women that were transfused in the peripartum period from January, 2014 to July, 2018. Cases were compared to the next age matched control to deliver at our institution. The primary objective was to determine the proportion of patients with iron deficiency in pregnancy or anemia in pregnancy in cases and controls. Charts were reviewed for predisposing risk factors for iron deficiency, laboratory measures of iron deficiency and anemia, iron supplementation history and maternal and fetal outcomes. Factors associated with peripartum transfusion were analyzed using a multivariate logistic regression.

Results

169 of 18, 294 (0.9%) women were transfused in the peripartum period and 64 (44%) of those transfused received 1 unit. Iron deficiency or anemia were present in 103 (71%) transfused women and 74 (51%) control women in pregnancy (OR 2.34, 95% CI: 3.7–18.0). Multivariate analysis identified social work involvement (adjusted OR 4.1, 95% CI: 1.8–10.1), intravenous iron supplementation in pregnancy (adjusted OR 3.8, 95% CI: 1.2–17.4) and delivery by unscheduled cesarean section (adjusted OR 2.8, 95% CI: 1.3–6.2) as significant predictors of peripartum transfusion.

Conclusions

Pregnant women being followed by a social worker, receiving intravenous iron supplementation in pregnancy or who deliver by unscheduled cesarean section are more likely to receive a red blood cell transfusion. Women with iron deficiency or anemia in pregnancy are at increased risk of peripartum blood transfusions and warrant early and rigorous iron supplementation.

A curious case of delayed hemolytic transfusion reaction with evanescent antibodies in a patient with hereditary hemorrhagic telangiectasia

BACKGROUND

Delayed hemolytic reactions are potential complications of incompatible transfusions and are usually associated with the identification of a new antibody on serologic studies, following a second immunization event. However, in rare cases, the antibody investigation remains negative even if the clinical presentation would lead one to suspect otherwise.

CASE REPORT

A 44-year-old woman with hereditary hemorrhagic telangiectasia presented to the emergency department with hematuria and low back pain after she had received three units of RBCs 2 weeks earlier. Hematology and biochemistry results were consistent with delayed hemolytic transfusion reaction, but surprisingly, serologic antibody investigations were negative. It was only when her plasma was tested with enzyme (ficin)-treated panel cells that anti-e was finally detected, with a 3+ reaction with all homozygous e+ cells. No reaction was seen with heterozygous e+ cells. Four months later, an anti-K was also detected on standard panels, while the anti-e remained detectable only with ficin-treated panel cells. Three years later, both antibodies had vanished and remained undetectable. The weakness of anti-e reaction, combined with the quick evanescence of both antibodies led to the suspicion of a potential underlying immunodeficiency disorder, which was confirmed by low immunoglobulin levels on two occasions.

CONCLUSION

To our knowledge, this is the first case of immunodeficiency disorder diagnosed after the identification of evanescent antibody reactions. This case also outlines the importance of a good clinical history that should lead to further investigations when a hemolytic transfusion reaction is suspected.

Blood group antigen and phenotype prevalence in the Korean population compared to other ethnic populations and its association with RBC alloantibody frequency

OBJECTIVES

This study aimed to analyse the allele frequency of blood group antigens in the Korean population and other ethnic populations and the association of blood group antigens with red blood cell (RBC) alloantibodies.

BACKGROUND

Blood group antigen genotyping can support patients undergoing frequent transfusions who have alloantibodies and antibodies against high-prevalence blood group antigens.

METHODS

Twenty-nine single nucleotide variations and 37 blood group antigens were tested. Samples requested for routine blood typing were collected from Jan to Apr 2016. Genotyping was performed on 145 Korean samples and was confirmed by bidirectional sequencing and serologic tests. The allele frequency data were compared with previous genotyping datasets (three datasets from Korea and one each from China, Europe, Asia, and the USA). Alloantibody frequencies and blood group antigens from the electronic medical record of 1772 cases were examined.

RESULTS

E antigen was higher in the Korean population compared to that of Asian and European populations. K, Kp^a , Fy^b and Do^a allele frequencies were lower compared to other ethnic populations. RBC alloantibodies with frequencies (%) greater than 1% from the 1772 cases were as follows: anti-E, 36·7%, anti-C, 17·7%; anti-c 7·39%; anti-M, 5·9%; anti-e, 5·2%; anti-Jk^a , 2·9%; and anti-Fy^a , 1·1%. Blood group antigens and alloantibody frequencies revealed inverse trends that did not reach statistical significance.

CONCLUSION

The allele frequency of blood group antigens assessed by high-throughput methods provided reliable and valuable information that could be used for maintaining donor pools and providing compatible blood for genotyped patients.

A regional massive hemorrhage protocol developed through a modified Delphi technique

BACKGROUND

A massive hemorrhage protocol (MHP) enables rapid delivery of blood components in a patient who is exsanguinating pending definitive hemorrhage control, but there is variability in MHP implementation rates, content and compliance owing to challenges presented by infrequent activation, variable team performance and patient acuity. The goal of this project was to identify the key evidence-based principles and quality indicators required to develop a standardized regional MHP.

METHODS

A modified Delphi consensus technique was performed in the spring and summer of 2018. Panellists used survey links to independently review and rate (on a 7-point Likert scale) 43 statements and 8 quality indicators drafted by a steering committee composed of transfusion medicine specialists and technologists, and trauma physicians. External stakeholder input from all hospitals in Ontario was sought.

RESULTS

Three rounds were held with 36 experts from diverse clinical backgrounds. Consensus was reached for 42 statements and 8 quality indicators. Additional modifications from external stakeholders were incorporated to form the foundation for the proposed MHP.

INTERPRETATION

This MHP template will provide the basis for the design of an MHP toolkit, including specific recommendations for pediatric and obstetrical patients, and for hospitals with limited availability of blood components or means to achieve definitive hemorrhage control. We believe that harmonization of MHPs in our region will simplify training, increase uptake of evidence-based interventions, enhance communication, improve patient comfort and safety, and, ultimately, improve patient outcomes.

Complement activation during intravascular hemolysis: Implication for sickle cell disease and hemolytic transfusion reactions

Intravascular hemolysis is a hallmark of a large spectrum of diseases, including the sickle cell disease (SCD), and is characterized by liberation of red blood cell (RBC) degradation products in the circulation. Released Hb, heme, RBC fragments and microvesicles (MVs) exert pro-inflammatory, pro-oxidative and cytotoxic effects and contribute to vascular and tissue damage. The innate immune complement system not only contributes to the RBC lysis, but it is also itself activated by heme, RBC MVs and the hypoxia-altered endothelium, amplifying thus the cell and tissue damage. This review focuses on the implication of the complement system in hemolysis and hemolysis-mediated injuries in SCD and in cases of delayed hemolytic transfusion reactions (DHTR). We summarize the evidences for presence of biomarkers of complement activation in patients with SCD and the mechanisms of complement activation in DHTR. We discuss the role of antibodies-dependent activation of the classical complement pathway as well as the heme-dependent activation of the alternative pathway. Finally, we describe the available evidences for the efficacy of therapeutic blockade of complement in cases of DHTR. In conclusion, complement blockade is holding promises but future prospective studies are required to introduce Eculizumab or another upcoming complement therapeutic for DHTR and even in SCD.

Predisposing factors for anti-D immune response in D- patients with chronic liver disease transfused with D+ platelet concentrates

BACKGROUND

Recent reports have indicated that the risk of anti-D alloimmunization following D-incompatible platelet (PLT) transfusion is low in hematology and oncology patients. We investigated the rate of anti-D alloimmunization in RhD-negative (D^- ) patients with chronic liver disease transfused with D⁺ platelet concentrates (PCs) and the factors involved, at a liver transplant (LT) center.

STUDY DESIGN AND METHODS

We reviewed the blood bank database from January 2003 to October 2016. D^- patients who had received D⁺ PLT transfusions were eligible if they had undergone antibody screening at least 28 days after the first D⁺ PC transfusion, had no previous or concomitant exposure to D⁺ blood products, and had not received anti-D immunoglobulins.

RESULTS

Six of the 56 eligible patients (10.7%) had anti-D antibodies. All had received whole blood-derived PCs. Four of 20 patients (20%) untransplanted or transfused before LT and only two of 36 patients (5.6%) transfused during or after LT produced anti-D antibodies. These two patients were on maintenance immunosuppression based on low-dose steroids and tacrolimus. The factors identified as significantly associated with anti-D immune response were the presence of red blood cell immune alloantibodies before D⁺ PLT transfusion (p = 0.003), and D⁺ PLT transfusion outside the operative and postoperative (5 days) periods for LT (p = 0.023).

CONCLUSION

D^- patients with chronic liver disease transfused with D⁺ PLTs before LT are at high risk of developing anti-D antibodies. Preventive measures should be considered for these patients.

Comparison of two column agglutination tests for red blood cell antibody testing

Background

Several sensitive methods are available for red blood cell (RBC) antibody screening. Among these, gel and glass card systems have demonstrated comparably good performance in retrospective studies and are widely used in routine patient diagnostics, but their performance in prospective studies has not been sufficiently characterised.

Patients and methods

Gel card (Bio-Rad DiaMed) and glass bead-based (Ortho Clinical Diagnostics) column agglutination technologies were used to screen for antibodies prospectively (group A) and for antibody identification in stored and fresh samples known to contain RBC antibodies retrospectively (group B). Untreated reagent RBCs and either papain-treated (Bio-Rad) or ficin-treated panel C cells (Ortho) were used for antibody identification.

Results

RBC-reactive antibodies were detected in 22 of 1000 group A samples, three of which tested positive only by gel card agglutination, and four only by glass bead agglutination (including one false positive each). Group B comprised 202 sera with known antibodies: 33 of these samples contained 36 antibodies detected only by gel card agglutination, whereas 9 samples contained antibodies detectable only by glass bead-based agglutination. Discrepancies mostly involved weak antibodies reactive by enzyme only. Two sera contained antibody mixtures that neither system detected completely. Of note, in antibody differentiation batches one and two, anti-Lu^a was reactive in 7 of 7 and 1 of 8 samples, respectively.

Conclusion

Both column agglutination tests for red cell antibodies had equal sensitivity and specificity with unstored samples. In stored samples, weak and enzyme-only antibodies were more frequently detected with the gel card system.

Clinical outcome of transfusions with extended red blood cell matching in β-thalassemia patients: A single-center experience

BACKGROUND

The development of alloantibodies may complicate the management of patients with β-thalassemia. An extended antigenic matching may reduce the risk of alloimmunization. Our previous study showed that the introduction of molecular red blood cell (RBC) typing allows finding suitable blood units for multi-transfused patients. The aim of this study was to evaluate the benefit of RBC transfusion with extended antigenic match.

MATERIALS AND METHODS

At the University of Campania "L. Vanvitelli", we selected β-thalassemia major patients (age ≤23 years), without preformed alloantibodies. Data of patients receiving transfusion of leukoreduced RBC units for a period of one year with partial better match (PBM) including ABO, RhD, C/c, E/e, K/k antigens and consecutive one year with extended match (EM) including ABO, RhD, C/c, E/e, K/k, Fy^a/Fy^b, Jk^a/Jk^b, M/N, S/s antigens, were compared.

RESULTS

Eighteen patients, 8 males and 10 females with a mean age of 15.4 years (6.4 SD) received a mean number of 41.2 (6.0 SD) RBC units transfused with PBM and 41.8 (6.2 SD) with EM protocols. After two years of RBC transfusions with both antigen matching protocols, no new alloantibodies were developed in patients. No significant differences in Hb concentration and volume of RBC transfused were found between PBM and EM protocols.

CONCLUSIONS

Thalassemia patients may benefit from receiving RBC transfusions based on extended antigen matching as demonstrated by the lack of new alloantibodies. However, our data show a high concordance between PBM and EM protocols considering pre-transfusion Hb, increment of Hb and volume of RBC transfused.

Shifting ground and gaps in transfusion support of patients with hematological malignancies

The transfusion support of hematological malignancies considers 2 dimensions: the quantity of what we order (in terms of triggers, doses, targets, and intervals), and the special qualities thereof (with respect to depths of matching and appropriate product modifications). Meanwhile, transfusion-related enhancements in the quantity and quality of life may not be dose dependent but rather tempered by unintended patient harms and system strains from overexposure. Evidence and guidelines concur in endorsing clinically noninferior conservative red blood cell (RBC) transfusion care strategies (eg, triggering at hemoglobin <7-8 g/dL and in single-unit doses for stable, nonbleeding inpatients). However, the unique subpopulation of patients with hematological malignancies who are increasingly managed on an outpatient basis, and striving at least as much for quality of life as quantity of life, is left on the edges of these recommendations, with more questions than answers. If a sufficiently specific future wave of evidence can satisfy the concerns (and contest the assumptions) of the remaining proponents of liberalism, and if conservatism is broadly adopted, savings may be potentially immense. These savings can then be reinvested to address other gaps and inconsistencies in RBC transfusion care, such as the best achievable degrees of prophylactic antigen matching that can minimize alloimmunization-related service delays and reactions.

A Conceptual Framework for Optimizing Blood Matching Strategies: Balancing Patient Complications Against Total Costs Incurred

Alloimmunization is currently the most frequent adverse blood transfusion event. Whilst completely matched donor blood would nullify the alloimmunization risk, this is practically infeasible. Current matching strategies therefore aim at matching a limited number of blood groups only, and have evolved over time by systematically including matching strategies for those blood groups for which (serious) alloimmunization complications most frequently occurred. An optimal matching strategy for controlling the risk of alloimmunization however, would balance alloimmunization complications and costs within the entire blood supply chain, whilst fulfilling all practical requirements and limitations. In this article the outline of an integrated blood management model is described and various potential challenges and prospects foreseen with the development of such a model are discussed.

Red Blood Cell Alloimmunization in the Pregnant Patient

Alloimmunization to red blood cell (RBC) antigens represents a challenge for physicians caring for women of child bearing potential. Exposure to non-self RBC antigens may occur during transfusion or pregnancy leading to the development of antibodies. If a subsequent fetus bears that antigen, maternal antibodies may attack the fetal red blood cells causing red cell destruction and clinically significant hemolytic disease of the fetus and newborn (HDFN). In the most severe cases, HDFN may result in intrauterine fetal demise due to high output cardiac failure, effusions and ascites, known as "hydrops fetalis". This article reviews strategies for management and prevention of RBC alloimmunization in women of child bearing potential.

Platelet Transfusion Induces Alloimmunization to D and Non-D Rhesus Antigens

Background

Platelet concentrates (PC) contain residual contaminating red blood cells (RBC), being higher in pooled buffy coat PC (BC-PC) than in apheresis units (AP-PC). Data about PC-induced alloimmunization against non-D Rhesus (Rh) antigens are limited.

Methods

For all newly detected RhD and non-D alloantibodies between August 2015 and September /2017 we prospectively evaluated if they were triggered through PC by analyzing for incompatible RBC and/or PC transfusions.

Results

We found 5,799 positive results in 89,190 antibody screening tests. We identified 13 newly detectable Rh antibodies through incompatible PCs in 11 patients: 6× anti-D, 4× anti-E, 2× anti-c, 1× anti-f. They received a total of 156 PC (83 BC-PC; 73 AP-PC): 5 patients received incompatible BC-PC only, 1 patient received incompatible AP-PC only, 5 patients received incompatible BC-PC and AP-PC. Quality control showed a mean (range) of 0.304 (0.152-1.662) and 0.014 (0.003-0.080) × 10⁹ RBC/l for BC-PC and AP-PC, respectively. Ten of the 11 patients received RBC transfusions, all of them being antigen-negative for the alloantibodies identified.

Conclusions

PC transfusions may not only induce RhD alloimmunization, but also immunization against further Rh antigens such as c, E, and f. The risk seems higher for BC-PC than for AP-PC. The results may have impact on future recommendations of PC transfusion with respect to Rh compatibility and upper limits of RBC contamination.

Red blood cell alloimmunization: new findings at the bench and new recommendations for the bedside

PURPOSE OF REVIEW

To summarize recent discoveries from clinical studies and animal models that contribute to understanding the alloimmune response to non-ABO blood group antigens.

RECENT FINDINGS

Several studies have confirmed high rates of alloimmunization among patients requiring chronic red blood cell (RBC) transfusion. Moreover, 'triggers' for alloantibody development in the transfusion setting have been identified, with a number of investigations linking recipient inflammation to a higher likelihood of alloimmunization. Additional associations between human leukocyte antigen expression and CD4 T-cell markers in 'responder' or 'nonresponder' humans have been revealed. Recent animal studies have described novel mechanistic properties by which the alloimmune response is governed, including the critical role played by dendritic cells in transfusion-associated alloimmunization. New light has also been shed on the properties of alloantibodies developed as a result of pregnancy, as well as mechanisms through which such alloimmunization may be prevented.

SUMMARY

Many of the clinical/biological factors that contribute to the RBC alloimmune response have been further elucidated. This knowledge will be applied to identify individuals most likely to mount an immune response to RBC antigens, such that appropriate resources and strategies for preventing alloimmunization (or mitigating its harmful effects) can be implemented.

Acute Hemolytic Transfusion Reaction Caused by a Red Cell Antibody That Was Missed by Pretransfusion Testing Using Tube Method

Pretransfusion testing is very important to prevent transfusion of incompatible red cells, which might result in a hemolytic transfusion reaction. This includes the detection of antibodies in recipients' serum and compatibility testing between donor cells and recipient serum. The most commonly used methods include gel and tube techniques. We present a case in which an anti-E alloantibody was detected by gel method but not by tube testing. As a result, red cells that were retrospectively phenotyped as positive for E antigen were inadvertently selected and transfused after crossmatch using the same tube method. After transfusion, the patient developed signs of hemolytic transfusion reaction. This case highlights the potential risk of transfusion of incompatible red cells when alloantibody detection is solely relied on tube testing.

From Donor to Recipient: Considerations for Blood Transfusion Outcomes Research

Donated blood can be broken down into blood components for use in patient care. This article focuses primarily on packed red blood cells (PRBCs), as they experience breakdown during storage that may adversely impact patient outcomes. Patients require PRBC transfusions for a number of clinical reasons. Although transfusions of PRBCs provide some clinical benefit, they are also associated with increased morbidity and mortality across multiple patient populations, albeit the mechanisms underlying this relationship remain unclear. With an aging, more acutely ill population requiring aggressive treatment and a lack of transfusion alternatives, research focused on PRBCs has gained momentum. Proper interpretation of research findings on the part of clinicians depends on accurate data collection that includes aspects of both the transfused blood components and the recipients. The purpose of this article is to examine stored PRBC factors, blood-donor characteristics, transfusion-specific factors, and patient-specific characteristics as they relate to patient outcomes research. Challenges associated with performing and interpreting outcomes of transfusion-related research are presented. Implications of current evidence for patient care, such as awareness of benefits as well as risks associated with blood component transfusion, are also provided.

Red blood cell alloimmunization in 184 patients with myeloid neoplasms treated with azacitidine - A retrospective single center experience

Alloimmunization to Red Blood Cell (RBC) antigens frequently occurs in patients with myeloid neoplasms (AML, MDS and CMML) and potentially poses the patient at risk for delayed hemolytic transfusion reactions and limited supply of compatible RBC-units. However, there is comparatively little data on transfusion associated characteristics in this patient cohort. We therefore retrospectively analyzed transfusion requirements and clinical outcomes of 184 patients with myloid neoplasms treated with azacitidine at the Paracelsus Medical University Salzburg, which were included in the Austrian Registry of Hypomethylating Agents. The mean blood component requirements for AML, MDS and CMML were 39.8, 67.4 and 31.4 RBC units and 31.7, 27.6 and 19.1 platelet (PLT) units respectively. In spite of an extended and stringent RBC unit matching policy (ABO, RhD, RhCcEe and K antigens), 20 (11%) patients formed at least one alloantibody ("allo-group"), whereas 164 patients (89%) did not ("non-allo-group"). The most frequent antibody specificity was anti-E, followed by anti-Wra -Lua, -D, -C and -Jka. Alloimmunization was associated with higher numbers of transfused RBC units (68 vs. 38; p=0.001), as well as with longer time under transfusion (16.7 vs. 9.4 months; p=0.014). Median overall survival (OS) did not differ significantly between the "allo"- and "non-allo-group".

Acquired red blood cell alloantibodies in transfused patients of 80 years or over: a 2008-2013 national haemovigilance survey

BACKGROUND

As transfusion in the elderly patients has increased over the last decades, and with the aim of improving blood policy, post-transfusion red blood cell alloimmunisation, a delayed serological transfusion reaction, was investigated in patients 80 years old or over.

MATERIALS AND METHODS

For every adverse reaction to a transfusion, a report is sent to the French haemovigilance database. All cases of red blood cell alloimmunisation reported in the haemovigilance database were collected, and an analysis was performed on those cases in transfused patients 80 years old or over.

RESULTS

There were 11,625 reports of red blood cell alloimmunisation from 1 January, 2008 to 31 December, 2013, of which 3,617 (31.1%) occurred in patients 80 years old or over. Among this subgroup, red blood cell concentrates were the most frequently involved blood component (3,482 reports, 96.3%). Red blood cell alloimmunisation after transfusion of platelet concentrates was also notified (132 reports, 3.7%). Anti-KEL1 was the most frequent antibody (874 reports, 24.2%). The imputability of the blood component was certain in 2,340 cases (64.7%) and probable in 1,078 (29.8%). In 2013, the incidence of red blood cell alloimmunisation was 4.14 per 1,000 transfused patients aged 80 years old or over.

DISCUSSION

In a 6-year national survey in which 40,570 reports were made, there were 3,617 cases of red blood cell alloimmunisation in transfused recipients of 80 years old or over. This delayed serological transfusion reaction is not rare. Red blood cell concentrates were predominantly involved, but cases caused by platelet concentrates were also described. In order to prevent alloimmunisation in the elderly, several factors must be evaluated before transfusing matched red blood cell concentrates: the patient's age, pathology and its outcome, the type of transfusion support (chronic or not), life expectancy, and blood product availability.

Red cell alloimmunisation in patients with different types of infections

Red cell alloantigen exposure can cause alloantibody‐associated morbidity. Murine models have suggested that inflammation modulates red cell alloimmunisation. This study quantifies alloimmunisation risks during infectious episodes in humans. We performed a multicentre case–control study within a source population of patients receiving their first and subsequent red cell transfusions during an 8‐year follow‐up period. Patients developing a first transfusion‐induced red cell alloantibody (N = 505) were each compared with two similarly exposed, but non‐alloimmunised controls (N = 1010) during a 5‐week ‘alloimmunisation risk period’ using multivariate logistic regression analysis. Transfusions during ‘severe’ bacterial (tissue‐invasive) infections were associated with increased risks of alloantibody development [adjusted relative risk (RR) 1·34, 95% confidence interval (95% CI) 0·97–1·85], especially when these infections were accompanied with long‐standing fever (RR 3·06, 95% CI 1·57–5·96). Disseminated viral disorders demonstrated a trend towards increased risks (RR 2·41, 95% CI 0·89–6·53), in apparent contrast to a possible protection associated with Gram‐negative bacteraemia (RR 0·58, 95% CI 0·13–1·14). ‘Simple’ bacterial infections, Gram‐positive bacteraemia, fungal infections, maximum C‐reactive protein values and leucocytosis were not associated with red cell alloimmunisation. These findings are consistent with murine models. Confirmatory research is needed before patients likely to develop alloantibodies may be identified based on their infectious conditions at time of transfusion.

Impact of azacitidine on red blood cell alloimmunisation in myelodysplastic syndrome

BACKGROUND

The incidence of alloimmunisation in myelodysplastic syndromes (MDS) during the era of supportive treatment ranges from 9 to 56%. However, it is unknown if the widespread use of hypomethylating agents has changed the risk of immunisation. The aim of this study is to evaluate the impact of azacitidine (AZA) therapy on red blood cell (RBC) alloimmunisation in transfused patients with MDS, myelodysplastic syndromes/myeloproliferative syndromes (MDS/MPS) and secondary acute myeloid leukaemia (AML).

MATERIAL AND METHODS

We have analysed retrospectively all patients with MDS, MDS/MPS and secondary AML from MDS, who received their first transfusion in our hospital between January 1995 and December 2014. We have assessed the impact of age, sex, RBC and platelets units transfused, and AZA treatment on developing alloantibodies.

RESULTS

In our study, the number of RBC units transfused increased the risk of developing alloantibodies. However aging and the treatment with AZA were associated with a lower rate of alloimmunisation.

DISCUSSION

Patients with MDS, MDS/MPS and secondary AML who received treatment with AZA developed RBC antibodies at a lower rate than control group. We suggest that aging and immunosuppression due to AZA therapy could develop an immunological tolerance with a weak response to allotransfusions.