A prospective study of the incidence of red cell allo-immunisation following transfusion

Screening for new red blood cell alloantibodies after transfusion in patients with sickle cell disease

BACKGROUND

Patients with sickle cell disease (SCD) are frequent recipients of red blood cell (RBC) transfusions and are at risk for RBC alloimmunization. RBC alloimmunization is diagnosed by identifying RBC alloantibodies as part of pre-transfusion testing, but this testing fails to detect alloantibodies that have evanesced. It may be beneficial to screen for new RBC alloantibody development after transfusion before possible antibody evanescence.

STUDY DESIGN AND METHODS

Our institution started a new initiative for episodically transfused patients with SCD to obtain at least one antibody screen 2-6 months after transfusion as part of their clinical care. A database was created to prospectively track all transfused patients for 1 year and their post-transfusion antibody screen results. Patients received prophylactically CEK-matched RBC units.

RESULTS

During the study year, 138 patients with SCD received a total of 242 RBC transfusions. Patients with a history of an RBC alloantibody (n = 13, 9.4%) had previously received more RBC units than non alloimmunized patients (median 11 vs. 2 RBC units, p = .0002). A total of 337 post-transfusion antibody screens were obtained in 127 patients (92.0%) with 110 patients (79.7%) having at least one antibody screen 2-6 months post-transfusion. With this prospective testing, two new RBC alloantibodies (anti-C and -M) were identified in two patients.

CONCLUSION

It is feasible to test for new RBC alloantibody development in most episodically transfused patients with SCD as part of their routine care. The yield of this screening appears low with CEK matching, but it could still provide important information for individual patients.

Red blood cell alloimmunization and sickle cell disease: a narrative review on antibody induction

The high prevalence of red blood cell (RBC) alloantibodies in people with sickle cell disease (SCD) cannot be debated. Why people with SCD are so likely to form RBC alloantibodies, however, remains poorly understood. Over the past decade, a better understanding of non-ABO blood group antigen variants has emerged; RH genetic diversity and the role this diversity plays in RBC alloimmunization is discussed elsewhere. Outside of antigen variants, the immune systems of people with SCD are known to be different than those of people without SCD. Some of these differences are due to effects of free heme, whereas others are impacted by hyposplenism. Descriptive studies of differences in white blood cell (WBC) subsets, platelet counts and function, and complement activation between people with SCD and race-matched controls exist. Studies comparing the immune systems of alloimmunized people with SCD to non-alloimmunized people with SCD to race-matched controls without SCD have uncovered differences in T-cell subsets, monocytes, Fcγ receptor polymorphisms, and responses to free heme. Studies in murine models have documented the role that recipient inflammation plays in RBC alloantibody formation, with human studies reporting a similar association. Murine studies have also reported the importance of type 1 interferon (IFNα/β), known to play a pivotal role in autoimmunity, in RBC alloantibody formation. The goal of this manuscript is to review existing data on factors influencing RBC alloantibody induction in people with SCD with a focus on inflammation and other immune system considerations, from the bench to the bedside.

Characterization of circulating and cultured Tfh-like cells in sickle cell disease in relation to red blood cell alloimmunization status

BACKGROUND

People living with sickle cell disease (SCD) are prone to red blood cell (RBC) alloimmunization. We hypothesized that subjects with alloantibodies (responders) would have differences in circulating T-follicular helper (Tfh)-like cells compared to subjects without alloantibodies (non-responders).

MATERIALS AND METHODS

Peripheral blood mononuclear cells were collected from 28 subjects, including those with SCD and controls. Circulating CD4 T-cell subsets were first evaluated at baseline. CD4 T-cell subsets were also evaluated after naïve CD4 T-cells were differentiated into Tfh-like cells following in vitro culture with CD3/CD28 beads, IL-7, IL-12, and Activin A. Transfusion and alloantibody histories were extracted from the electronic medical record.

RESULTS

Non-responders had a lower percentage of CD45RA negative Tmemory cells than responders or controls (p<0.05). Notably, there were no differences in circulating Tfh-like cells between any group. However, naïve CD4 T-cells from subjects with SCD were more likely to express CXCR5 after in vitro culture than cells from controls. After culture, CXCR5 expressing cells from responders were more likely to express PD1 and ICOS (16.43 %, sd. 20.23) compared to non-responders (3.69 %, s.d. 3.09) or controls (2.78 %, s.d. 2.04).

DISCUSSION

The tendency for naïve CD4 T-cells from responders to differentiate into Tfh-like cells after in vitro culture may suggest these cells are prepared to assist B-cells with antibody production regardless of antigen specificity. Further studies are needed, but it is possible that these results may explain why some responders form RBC alloantibodies with multiple specificities, in addition to RBC autoantibodies and HLA alloantibodies.

Prevalence and risk factors for RBC alloantibodies in blood donors in the Recipient Epidemiology and Donor Evaluation Study-III (REDS-III)

BACKGROUND

Little information exists on red blood cell (RBC) alloimmunization in healthy US blood donors, despite the potential significance for donors themselves, blood recipients, and the blood center.

STUDY DESIGN AND METHODS

Donor/donation data were sourced from the Recipient Epidemiology and Donor Evaluation Study-III, which contains information from four US blood centers during 2012 through 2016. Multivariable logistic regression was used to assess prevalence of positive antibody screen by donor demographics, blood type, parity, and transfusion history.

RESULTS

More than 2 million units were collected from 632,378 donors, with 0.51% of donations antibody screen positive and 0.77% of donors having at least one positive antibody screen. The most common antibody specificities were D (26.4%), E (23.8%), and K (21.6%). Regression analysis indicated that increasing age, female sex, D-negative status, and history of transfusion and pregnancy were positively associated with a positive antibody screen. Prior transfusion history was most strongly associated with a positive antibody screen, with donors reporting a prior transfusion having a higher adjusted odds ratio (3.9) of having a positive antibody screen compared to donors reporting prior pregnancy (adjusted odds ratio, 2.0). Though transfusion was a more potent immune stimulus for RBC alloantibody formation than pregnancy, the sheer number of previously pregnant donors contributed to pregnancy being a risk factor for the majority of clinically significant RBC alloantibodies detected in females.

CONCLUSION

These findings on prevalence of and risk factors for RBC antibodies may have implications for future medical care of donors and for operations at blood centers.

The Role of the Immunological Synapse in Differential Effects of APC Subsets in Alloimmunization to Fresh, Non-stored RBCs

Background: Each year, over 5 million red blood cell (RBC) transfusions are administered to patients in the USA. Despite the therapeutic benefits of RBC transfusions, there are associated risks. RBC-specific alloantibodies may form in response to antigenic differences between RBC donors and recipients; these alloantibodies can be a problem as they may mediate hemolysis or pose barriers to future transfusion support. While there is currently no reliable way to predict which RBC recipients will make an alloantibody response, risk factors such as inflammation have been shown to correlate with increased rates of RBC alloimmunization. The underlying mechanisms behind how inflammation mediates alloantibody production are incompletely defined.

Methods: To assess erythrophagocytosis, mice were treated with PBS or inflammatory stimuli followed by a transfusion of allogeneic RBCs labeled with a lipophilic dye. At multiple time points, RBC consumption and expression of activation makers by leukocytes was evaluated. To determine which antigen presenting cell (APC) subset(s) were capable of promoting allogeneic T cell activation, sorted leukocyte populations (which had participated in erythrophagocytosis) were co-cultured in vitro with allogeneic CD4+ T cells; T cell proliferation and ability to form immunological synapses with APCs were determined.

Results: Upon transfusion of fresh allogeneic RBCs, multiple APCs consumed transfused RBCs. However, only CD8+ and CD11b+ dendritic cells formed productive immunological synapses with allogeneic T cells and stimulated proliferation. Importantly, allogeneic T cell activation and RBC alloantibody production occurred in response to RBC transfusion alone, and transfusion in the context of inflammation enhanced RBC consumption, the number of immune synapses, allogeneic T cell proliferation, and the rate and magnitude of alloantibody production.

Conclusions: These data demonstrate that regardless of the ability to participate in RBC consumption, only a subset of APCs are capable of forming an immune synapse with T cells thereby initiating an alloantibody response. Additionally, these data provide mechanistic insight into RBC alloantibody generation.

[When A is not A anymore: problems and pitfalls with blood group typing]

Correct blood group typing is a prerequisite for transfusion. In most cases blood group determination is without problems; however, in individual cases various factors can complicate blood group determination and sometimes lead to confusing findings. For a better understanding the clinician should have basic knowledge of blood typing. Blood group determination usually covers the AB0 blood groups, Rhesus and Kell systems; in addition, a direct Coombs test and an antibody screening test for the detection of irregular antibodies in the recipient are performed. Confusion of patients, blood samples, results or preparations can lead to severe consequences due to incompatible transfusion and must be prevented. In this context, bedside blood type testing before transfusion is of utmost importance. Problems in laboratory analysis as well as patient-related factors, such as the existence of irregular antibodies against red blood cells can complicate the immunohematology diagnostics. Certain medications, such as daratumumab, lead to a significantly increased complexity in laboratory analyses. Massive transfusions can lead to chimerism with more than one population of circulating red blood cells. Hematopoetic stem cell transplantation can also lead to a change in blood groups as well as chimerism. In addition, there are various other rare causes that can result in difficulties in blood group determination, such as rare blood groups or rare disease-associated phenomena. In the case of problems in blood group determination, early and close cooperation with transfusion medicine is essential for the clinician.

Risk factors for red blood cell alloimmunization in the Recipient Epidemiology and Donor Evaluation Study (REDS-III) database

Despite the significance of red blood cell (RBC) alloimmunization, the lack of standardized registries in the US has prevented the completion of large studies. Data from 3·5 years of the Recipient Epidemiology and Donor Evaluation Study-III (REDS-III) recipient database, containing information from 12 hospitals, were studied. A RBC alloantibody responder had an antibody identified at any point during the study, and a non-responder had a negative antibody screen at least 15 days post-RBC transfusion. Demographics, blood type, ICD9/10 codes, and other potential correlates were evaluated. Of 319 177 (2·07%) screened patients, 6597 had a total of 8892 clinically significant RBC alloantibodies identified, with 75% being in the Rh or Kell families. Alloimmunization was more common in females (2·38%) than males (1·68%), and in RhD negative (2·82%) than RhD positive (1·94%) patients. Age, sex, RhD status and race were associated with being a responder, and certain diagnoses (including sickle cell disease or trait, systemic lupus erythematosus, rheumatoid arthritis and myelodysplastic syndrome) were more common among responders than non-responders. Data collected in this multi-centre recipient database provide the largest RBC alloimmunized patient cohort studied in the US, with previously known demographic and disease associations of responder status confirmed, and new associations identified.

Type I IFN Is Necessary and Sufficient for Inflammation-Induced Red Blood Cell Alloimmunization in Mice

During RBC transfusion, production of alloantibodies against RBC non-ABO Ags can cause hemolytic transfusion reactions and limit availability of compatible blood products, resulting in anemia-associated morbidity and mortality. Multiple studies have established that certain inflammatory disorders and inflammatory stimuli promote alloimmune responses to RBC Ags. However, the molecular mechanisms underlying these findings are poorly understood. Type I IFNs (IFN-α/β) are induced in inflammatory conditions associated with increased alloimmunization. By developing a new transgenic murine model, we demonstrate that signaling through the IFN-α/β receptor is required for inflammation-induced alloimmunization. Additionally, mitochondrial antiviral signaling protein-mediated signaling through cytosolic pattern recognition receptors was required for polyinosinic-polycytidylic acid-induced IFN-α/β production and alloimmunization. We further report that IFN-α, in the absence of an adjuvant, is sufficient to induce RBC alloimmunization. These findings raise the possibility that patients with IFN-α/β-mediated conditions, including autoimmunity and viral infections, may have an increased risk of RBC alloimmunization and may benefit from personalized transfusion protocols and/or targeted therapies.

Bortezomib decreases the magnitude of a primary humoral immune response to transfused red blood cells in a murine model

BACKGROUND

Few therapeutic options currently exist to prevent or to mitigate transfusion-associated red blood cell (RBC) alloimmunization. We hypothesized that bortezomib, a proteasome inhibitor currently being utilized for HLA alloantibody and ADAMTS13 autoantibody reduction, may be beneficial in a transfusion setting. Herein, we utilized a reductionist murine model to test our hypothesis that bortezomib would decrease RBC alloimmune responses.

STUDY DESIGN AND METHODS

Wild-type mice were treated with bortezomib or saline and transfused with murine RBCs expressing the human KEL glycoprotein. Levels of anti-KEL immunoglobulins in transfusion recipients were measured by flow cytometry. The impact of bortezomib treatment on recipient plasma cells (PCs) and other immune cells was also assessed by flow cytometry and immunofluorescence.

RESULTS

After bortezomib treatment, mice had a 50% reduction in splenic white blood cells and a targeted reduction in marrow PCs. Mice treated with bortezomib before the transfusion of KEL RBCs became alloimmunized in three of three experiments, although their serum anti-KEL IgG levels were 2.6-fold lower than those in untreated mice. Once a primary antibody response was established, bortezomib treatment did not prevent an anamnestic response from occurring.

CONCLUSION

To the extent that these findings are generalizable to other RBC antigens and to humans, bortezomib monotherapy is unlikely to be of significant clinical benefit in a transfusion setting where complete prevention of alloimmunization is desirable. Given the impact on PCs, however, it remains plausible that bortezomib therapy may be beneficial for RBC alloimmunization prevention or mitigation if used in combination with other immunomodulatory therapies.

Alloimmunization in multitransfused liver disease patients: Impact of underlying disease

Introduction:

Transfusion support is vital to the management of patients with liver diseases. Repeated transfusions are associated with many risks such as transfusion-transmitted infection, transfusion immunomodulation, and alloimmunization.

Materials and Methods:

A retrospective data analysis of antibody screening and identification was done from February 2012 to February 2014 to determine the frequency and specificity of irregular red-cell antibodies in multitransfused liver disease patients. The clinical and transfusion records were reviewed. The data was compiled, statistically analyzed, and reviewed.

Results:

A total of 842 patients were included in our study. Alloantibodies were detected in 5.22% of the patients. Higher rates of alloimmunization were seen in patients with autoimmune hepatitis, cryptogenic liver disease, liver damage due to drugs/toxins, and liver cancer patients. Patients with alcoholic liver disease had a lower rate of alloimmunization. The alloimmunization was 12.7% (23/181) in females and 3.17% (21/661) in males. Antibodies against the Rh system were the most frequent with 27 of 44 alloantibodies (61.36%). The most common alloantibody identified was anti-E (11/44 cases, 25%), followed by anti-C (6/44 cases, 13.63%).

Conclusion:

Our findings suggest that alloimmunization rate is affected by underlying disease. Provision of Rh and Kell phenotype-matched blood can significantly reduce alloimmunization.

Partial matching of blood group antigens to reduce alloimmunization in Western India

Red blood cell alloimmunization occurs due to the genetic disparity of red cell antigens between donor and recipient. In the present study, we report a spectrum of red cell alloantibodies characterized in patients with different clinical conditions in a reference center in India. Majority of the antibodies identified were against the blood group antigens c, D, E, M, N, S, s and Jka. Hence, apart from ABO and RhD, we recommend partial antigen matching between donor and patients for other Rh (C, c, E, e) and MNS blood group antigens to potentially reduce the risk of alloimmunization by 75%. Matching of Kell antigen is not recommended in Western India.

Prevalence of erythrocyte alloimmunization in polytransfused patients

OBJECTIVE

To determine the incidence and the rate of red blood cell alloimmunization in polytransfused patients.

METHODS

A polytransfused patient was defined as having received at least 6 units of red cell concentrates during a 3-month period. The records of all patients (n = 12,904) who had received red blood cell units were examined retrospectively by searching the computer database at Hospital Israelita Albert Einstein in São Paulo, Brazil, over a 6-year period, between 2003 and 2009.

RESULTS

During this time, 77,049 red cell concentrate transfusions were performed in 12,904 patients. There were 3,044 polytransfused patients, 227 of whom (7.5%) presented with irregular erythrocyte antibodies. The prevalence of alloantibody specificity was: Anti-E>anti-D>anti-K>anti-C>anti-Dia>anti-c>anti-Jka>anti-S in 227 polytransfused patients. We found combinations of alloantibodies in 79 patients (34.8%), and the most common specificities were against the Rh and/or Kell systems. These antibodies show clinical significance, as they can cause delayed hemolytic transfusion reactions and perinatal hemolytic disease. About 20% of the patients showed an IgG autoantibody isolated or combined with alloantibodies. Interestingly, a high incidence of antibodies against low frequency antigens was detected in this study, mainly anti-Dia.

CONCLUSION

Polytransfused patients have a high probability of developing alloantibodies whether alone or combined with autoantibodies and antibodies against low frequency antigens. Transfusion of red blood cells with a phenotype-compatible with RH (C, E, c), K, Fya, and Jka antigens is recommended for polytransfused patients in order to prevent alloimmunization and hemolytic transfusion reactions.

Risk factors for alloimmunisation in the general patient population

For hospitals providing services to regional populations, difficulties are associated with transferred patients with poorly communicated medical history and a risk of alloimmunisation. Identification of patients at risk would assist in treatment planning. A retrospective study of alloimmunised patients was undertaken, comparing the demographics and diagnoses of this population with a control patient population. A preponderance of diagnoses of Sepsis, Haematological Malignancy, GIT Bleeds and Renal Failure was demonstrated in the alloimmunised population. Consistent with prior studies, RhD negative patients and female patients were over-represented in the study group, which was also on average significantly older.

The Influence of Clinical and Biological Factors on Transfusion-Associated Non-ABO Antigen Alloimmunization: Responders, Hyper-Responders, and Non-Responders

In the context of transfusion medicine, alloimmunization most often refers to the development of antibodies to non-ABO red blood cell (RBC) antigens following pregnancy, transfusion, or transplantation. The development of RBC alloantibodies can have important clinical consequences, particularly in patients who require chronic transfusions. It has been suggested that alloimmunization is more common in some clinical circumstances and patient populations than in others. As such, individuals that develop alloantibodies are frequently referred to as 'responders' in the medical literature. In contrast, individuals that do not develop alloantibodies despite repeated exposures to non-self blood group antigens have been referred to as 'non-responders'. The purpose of this article is to review the phenomenon of RBC alloimmunization in the context of responders and non-responders to: i) establish a basic framework for alloimmunization as reported across several diverse patient populations; ii) more fully explore literature reports which support the concept of responders/non-responders regarding blood group antigen alloimmunization; iii) summarize the mechanisms that have been shown to predispose an individual to alloimmunization to determine how these factors may differentiate 'responders' from 'non-responders'; and iv) briefly discuss some practical approaches to prevent alloimmunization in patients who may be prone to alloantibody development.

Factors Influencing RBC Alloimmunization: Lessons Learned from Murine Models

Red blood cell (RBC) alloimmunization may occur following transfusion or pregnancy/delivery. Although observational human studies have described the immunogenicity of RBC antigens and the clinical significance of RBC alloantibodies, studies of factors influencing RBC alloimmunization in humans are inherently limited by the large number of independent variables involved. This manuscript reviews data generated in murine models that utilize transgenic donor mice, which express RBC-specific model or authentic human blood group antigens. Transfusion of RBCs from such donors into nontransgenic but otherwise genetically identical recipient mice allows for the investigation of individual donor or recipient-specific variables that may impact RBC alloimmunization. Potential donor-related variables include methods of blood product collection, processing and storage, donor-specific characteristics, RBC antigen-specific factors, and others. Potential recipient-related variables include genetic factors (MHC/HLA type and polymorphisms of immunoregulatory genes), immune activation status, phenotype of regulatory immune cell subsets, immune cell functional characteristics, prior antigen exposures, and others. Although murine models are not perfect surrogates for human biology, these models generate phenomenological and mechanistic hypotheses of RBC alloimmunization and lay the groundwork for follow-up human studies. Long-term goals include improving transfusion safety and minimizing the morbidity/mortality associated with RBC alloimmunization.

Responder individuality in red blood cell alloimmunization

Many different factors influence the propensity of transfusion recipients and pregnant women to form red blood cell alloantibodies (RBCA). RBCA may cause hemolytic transfusion reactions, hemolytic disease of the fetus and newborn and may be a complication in transplantation medicine. Antigenic differences between responder and foreign erythrocytes may lead to such an immune answer, in part with suspected specific HLA class II associations. Biochemical and conformational characteristics of red blood cell (RBC) antigens, their dose (number of transfusions and pregnancies, absolute number of antigens per RBC) and the mode of exposure impact on RBCA rates. In addition, individual circumstances determine the risk to form RBCA. Responder individuality in terms of age, sex, severity of underlying disease, disease- or therapy-induced immunosuppression and inflammation are discussed with respect to influencing RBC alloimmunization. For particular high-risk patients, extended phenotype matching of transfusion and recipient efficiently decreases RBCA induction and associated clinical risks.

Red blood cell alloimmunization mitigation strategies

Hemolytic transfusion reactions due to red blood cell (RBC) alloantibodies are a leading cause of transfusion-associated death. In addition to reported deaths, RBC alloantibodies also cause significant morbidity in the form of delayed hemolytic transfusion reactions. These alloantibodies may also cause morbidity in the form of anemia, with compatible RBC units at times being unable to be located for highly alloimmunized patients, or in the form of hemolytic disease of the newborn. Thus, preventing RBC alloantibodies from developing in the first place, or mitigating the dangers of existing RBC alloantibodies, would decrease transfusion-associated morbidity and mortality. A number of human studies have evaluated the impact on RBC alloimmunization rates of providing partially phenotypically or genotypically matched RBCs for transfusion, and a number of animal studies have evaluated the impact of single variables on RBC alloimmunization. The goal of this review is to take a comprehensive look at existing human and animal data on RBC alloimmunization, focusing on strategies that may mitigate this serious hazard of transfusion. Potential factors that impact initial RBC alloimmunization, on both the donor and recipient sides, will be discussed. These factors include, but are not limited to, exposure to the antigen and an ability of the recipient's immune system to present that antigen. Beyond these basic factors, coexisting "danger signals," which may come from the donor unit itself or which may be present in the recipient, also likely play a role in determining which transfusion recipients may become alloimmunized after RBC antigen exposure. In addition, to better understanding factors that influence the development of RBC alloantibodies, this review will also briefly discuss strategies to decrease the dangers of existing RBC alloantibodies.

Genomic analyses of RH alleles to improve transfusion therapy in patients with sickle cell disease

BACKGROUND

Red cell (RBC) blood group alloimmunization remains a major problem in transfusion medicine. Patients with sickle cell disease (SCD) are at particularly high risk for developing alloantibodies to RBC antigens compared to other multiply transfused patient populations. Hemagglutination is the classical method used to test for blood group antigens, but depending on the typing methods and reagents used may result in discrepancies that preclude interpretation based on serologic reactivity alone. Molecular methods, including customized DNA microarrays, are increasingly used to complement serologic methods in predicting blood type. The purpose of this study was to determine the diversity and frequency of RH alleles in African Americans and to assess the performance of a DNA microarray for RH allele determination.

MATERIAL AND METHODS

Two sets of samples were tested: (i) individuals with known variant Rh types and (ii) randomly selected African American donors and patients with SCD. Standard hemagglutination tests were used to establish the Rh phenotype, and cDNA- and gDNA-based analyses (sequencing, PCR-RFLP, and customized RHD and RHCE microarrays were used to predict the genotype).

RESULTS

In a total of 829 samples (1658 alleles), 72 different alleles (40 RHD and 32 RHCE) were identified, 22 of which are novel. DNA microarrays detected all nucleotides probed, allowing for characterization of over 900 alleles.

CONCLUSIONS

High-throughput DNA testing platforms provide a means to test a relatively large number of donors and potentially prevent immunization by changing the way antigen-negative blood is provided to patients. Because of the high RH allelic diversity found in the African American population, determination of an accurate Rh phenotype often requires DNA testing, in conjunction with serologic testing. Allele-specific microarrays offer a means to perform high-throughput donor Rh typing and serve as a valuable adjunct to serologic methods to predict Rh type. Because DNA microarrays test for only a fixed panel of allelic polymorphisms and cannot determine haplotype phase, alternative methods such as Next Generation Sequencing hold the greatest potential to accurately characterize blood group phenotypes and ameliorate the clinical course of multiply-transfused patients with sickle cell disease.

Alloimmunization screening after transfusion of red blood cells in a prospective study

Background

Several irregular red blood cell alloantibodies, produced by alloimmunization of antigens in transfusions or pregnancies, have clinical importance because they cause hemolysis in the fetus and newborn and in transfused patients.

Objective

a prospective analysis of patients treated by the surgical and clinical emergency services of Hospital de Clínicas of the Universidade Federal do Triângulo Mineiro (HC/UFTM), Brazil was performed to correlate alloimmunization to clinical and epidemiological data.

Methods

Blood samples of 143 patients with initial negative antibody screening were collected at intervals for up to 15 months after the transfusion of packed red blood cells. Samples were submitted to irregular antibody testing and, when positive, to the identification and serial titration of alloantibodies. The Fisher Exact test and Odds Ratio were employed to compare proportions.

Results

Fifteen (10.49%) patients produced antibodies within six months of transfusion. However, for 60% of these individuals, the titers decreased and disappeared by 15 months after transfusion. Anti-K antibodies and alloantibodies against antigens of the Rh system were the most common; the highest titer was 1:32 (anti-K). There was an evident correlation with the number of transfusions.

Conclusions

Given the high incidence of clinically important red blood cell alloantibodies in patients transfused in surgical and clinical emergency services, we suggest that phenotyping and pre-transfusion compatibilization for C, c, E, e (Rh system) and K (Kell system) antigens should be extended to all patients with programmed surgeries or acute clinical events that do not need emergency transfusions.

Incidence of Red Cell Alloantibody among the Transfusion Recipients of Universiti Kebangsaan Malaysia Medical Centre

Red blood cell alloimmunization is a common complication among the transfusion recipients. In Malaysia, multiple ethnicity causes genetic heterogeneity among the population which in turn can cause a wide variation of antibody. The objective of this study was to analyse the red cell alloantibody detected during the pre-transfusion testing. This was a cross-sectional study done in the blood bank of Universiti Kebangsaan Malaysia Medical Centre during the period of January-December 2010. The data was retrieved from the hospital laboratory information system. A total of 24,263 patients' blood samples were subjected for pre-transfusion testing. Antibody screening was done using an indirect antiglobulin test method. The positive samples were further identified for antibody specificity. Antibody screening tests were positive in 184 patients out of 24,263 samples with the incidence of 0.76 %. Autoantibodies and alloantibodies were detected in 39/184 (21.2 %) and 140/184 (76.1 %) of the patients respectively. In five patients (2.7 %) the antibody specificity remained undetermined. Total 161 alloantibodies were identified. The suspected Anti-Mia alloantibody was observed most frequently (49/161, 30.4 %) followed by anti-E (30/161, 18.6 %) and anti-D (22/161, 13.7 %). Anti-E and anti-c were the most common combination of multiple alloantibodies. In view of the high incidence of suspected Anti-Mia antibodies, more efforts are needed to look into the techniques for confirmation of the Anti-Mia antibodies. Besides that, we suggested that all multiply transfused patients should be phenotyped for the Rh system and to supply Rh phenotype specific blood in order to limit alloimmunization.

A detection of unexpected blood antibody at the time of transfusion was needed, during the operation -A case report-

To avoid the occurrence of fatal complications of blood transfusion, several tests are implemented before transfusion. The tests include ABO typing, Rh typing, cross-matching test and blood antibody screening test, and in usual they are completed before transfusion. However in the case of repetitive operations done via brief distance, reexamination for blood antibody tends to be omitted. After 2 previous operations, 30 years old male patient showed positive blood antibody screening during the third operation. Although antibody screening test performed before the first operation, no unexpected blood antibody was detected. During the third operation, after the decision to start transfusion was made, it took two hours to find appropriate blood. There was no significant deterioration of patient's condition but the loss of time could lead to critical consequences. We present this case to make anesthesiologists and surgeons aware of possibility of unexpected blood antibody detection after transfusion.

Transfusion of prion-filtered red cells does not increase the rate of alloimmunization or transfusion reactions in patients: results of the UK trial of prion-filtered versus standard red cells in surgical patients (PRISM A)

This study, conducted for the UK Blood Transfusion Services (UKBTS), evaluated the clinical safety of red cells filtered through a CE-marked prion removal filter (P-Capt™). Patients requiring blood transfusion for elective procedures in nine UK hospitals were entered into a non-randomized open trial to assess development of red cell antibodies to standard red cell (RCC) or prion-filtered red cell concentrates (PF-RCC) at eight weeks and six months post-transfusion. Patients who received at least 1 unit of PF-RCC were compared with a control cohort given RCC only. About 917 PF-RCC and 1336 RCC units were transfused into 299 and 291 patients respectively. Twenty-six new red cell antibodies were detected post-transfusion in 10 patients in each arm, an overall alloimmunization rate of 4.4%. Neither the treatment arm [odds ratio (OR) 0.93, 95% confidence interval (CI) 0.3, 2.5] nor number of units transfused (OR 0.95, 95% CI 0.8, 1.1) had a significant effect on the proportion of patients who developed new alloantibodies. No pan-reactive antibodies or antibodies specifically against PF-RCC were detected. There was no difference in transfusion reactions between arms, and no novel transfusion-related adverse events clearly attributable to PF-RCC were seen. These data suggest that prion filtration of red cells does not reduce overall transfusion safety. This finding requires confirmation in large populations of transfused patients.

Triple red blood cell alloantibody formation after bone-allograft transplantation

In this case report, we provide evidence for the possibility of red blood cell alloimmunization after bone-allograft transplantation. Here, we present a 13-year-old boy who received a bone allograft due to impending hip-luxation. Five months later he was shown to have developed three different alloantibodies: anti-D, anti-C and anti-E, which were induced by the bone allograft. Red blood cell alloimmunization is a possible adverse event when a patient is exposed to allogenic red blood cells. These antibodies may cause transfusion reactions when incompatible blood is administered. More importantly, these antibodies may cause severe, or even fatal, hemolytic disease of the fetus or newborn, stretching the importance of preventing antibody formation, especially in young women. This case demonstrates the importance of selecting rhesus phenotype compatible bone allografts.

[Red-blood-cell allo-immunization]

Red blood cell allo-immunization is the immune response of an individual to foreign red blood cell antigens not present on the surface of their own cells. The aim of that paper is to clarify the different factors influencing the antibody response against red blood cell antigens.

Red blood cell transfusion at Ullevål University Hospital--indications, consumption and blood group immunisation

BACKGROUND

Knowledge of clinical transfusion practice should be improved to ensure that therapy is optimally effective, to avoid waste of resources and to ensure a safe supply of blood.

MATERIAL AND METHOD

All patients who received a transfusion of red blood cell concentrate at Ullevål University Hospital in two 14-day periods in 2003 were included. Diagnoses, haemoglobin values and intervention codes were recorded from the patient records for which consent to access had been given. Blood samples were taken from consenting survivors to be tested for blood group immunisation.

RESULTS

348 patients were included. The median age was 62.8 years. They were given 1,162 concentrates in 471 transfusion episodes, of which 373 (79 %) consisted of one or two concentrates. As at 1 February 2009, 181 patients (52 %) were registered as having died. Access was possible to the records of 218 patients. The primary diagnosis was cancer for 76 patients (35 %), injuries for 36 (17 %) and cardiovascular disease for 34 (16 %). The transfusion was given to 89 (41 %) of patients in connection with a surgical intervention during the period covered by the patient records. A note about the transfusion was lacking in 46 (21 %) of the records. Transfusions were given to 52 patients whose haemoglobin concentration was above a threshold level of ≥ 8 g/100 ml (43 % of the patients). Blood group immunisation was found in one (3 %) of 38 survivors.

INTERPRETATION

Red blood cell transfusion is most commonly given to elderly patients with chronic disorders and uncertain long-term prognoses. The clinical documentation is not infrequently incomplete. There is probably scope for a reduction in consumption if indications are based more on established scientific evidence and well-defined transfusion protocols. Blood group immunisation is not a frequent complication.

Red-blood-cell alloimmunization and number of red-blood-cell transfusions

BACKGROUND

Patients receiving red-blood-cells may form antibodies against the alloantigens expressed by red-blood-cells, with the risk of serious morbidity and the need for extensive phenotype-matching in subsequent transfusions. The incidence of alloimmunization is considered variable for specific patient groups and for first time antibody formation. We therefore studied the cumulative incidence of the first formed alloantibody as a function of red-blood-cells exposure.

METHODS

We performed a new-user cohort among all previously non-transfused non-alloimmunized patients that received non-extended matched (ABO and RhD) red-blood-cells transfusions from January 2005 to December 2009 in our university medical centre. Alloimmunization incidences were estimated by Kaplan-Meier survival-analysis.

RESULTS

A total of 3002 previously non-transfused patients received 31103 red-blood-cell units. A first time alloantibody forming event was experienced by 54 (1·8%) patients. The cumulative incidence of alloimmunization was 1·0% at 5 units, 2·4% at 10 units, 3·4% at 20 units and 6·5% at 40 units of red-blood-cells transfused.

CONCLUSION

The risk to develop a first red-blood-cells alloantibody increases up to the 40th transfusion and is similar for men and women. More data are needed to examine the risk after 40th transfusion.

DNA-based methods in the immunohematology reference laboratory

Although hemagglutination serves the immunohematology reference laboratory well, when used alone, it has limited capability to resolve complex problems. This overview discusses how molecular approaches can be used in the immunohematology reference laboratory. In order to apply molecular approaches to immunohematology, knowledge of genes, DNA-based methods, and the molecular bases of blood groups are required. When applied correctly, DNA-based methods can predict blood groups to resolve ABO/Rh discrepancies, identify variant alleles, and screen donors for antigen-negative units. DNA-based testing in immunohematology is a valuable tool used to resolve blood group incompatibilities and to support patients in their transfusion needs.

Increased detection of clinically significant antibodies and decreased incidence of delayed haemolytic transfusion reaction with the indirect antiglobulin test potentiated by polyethylene glycol compared to albumin: a Japanese study

BACKGROUND

The indirect antiglobulin test (IAT) can be potentiated by agents such as polyethylene glycol (PEG-IAT) and albumin (Alb-IAT). PEG-IAT is generally regarded as superior to Alb-IAT for the detection of clinically significant red blood cell (RBC) antibodies. However, supporting data come from Caucasian-dominant populations. Non-Caucasian populations should be investigated as well.

MATERIAL AND METHODS

In this single-centre, retrospective, sequential study, Alb-IAT was used from 1989 to 1996 (8 years) and PEG-IAT from 1997 to 2008 (12 years). Pre-transfusion RBC alloantibody detection rates and specificity, post-transfusion alloantibody production, and the incidence of delayed haemolytic transfusion reaction were assessed and compared for the two periods.

RESULTS

Although overall RBC alloantibody detection rates were comparable, PEG-IAT more frequently detected clinically significant antibodies such as anti-E, anti-Fy(b), and anti-Jk(a), and less frequently detected insignificant antibodies such as anti-Le(b) and anti-P(1). New alloantibodies emerged comparably during the two periods. Delayed haemolytic transfusion reaction was less frequent during the PEG-IAT period (0.30% versus 0.12%, p<0.05).

CONCLUSION

PEG-IAT was superior in the detection of clinically significant antibodies, reduced the detection of insignificant antibodies, and prevented delayed haemolytic transfusion reaction better than Alb-IAT among Japanese transfusion recipients in this retrospective survey of limited power.

[Appearance of anti-red blood cell antibodies in 80 years old and over transfused patients: result of 3 years haemovigilance survey]

PURPOSE

Today most transfusions are given to people over 70. In order to evaluate the production and the circumstances of the appearance of red blood cells (RBC) allo-antibodies (Ab), a three-year study was performed in transfused patients aged 80 and over.

MATERIAL AND METHODS

Based on the Adverse Event Reports (AER) on RBC Ab from 2007 to 2009 in the Rhône-Alpes area, the prevalence and specificity of the RBC Ab, the type of blood component involved, the imputability and the previous transfusion and obstetrical history were studied.

RESULTS

Of 2,169 AER, 240 (11.1%) related to the appearance of RBC Ab; they included 150 females (F) patients (62.5%) and 90 males (M) (37.5%). The Rhesus (RH) blood group was most involved (75 AER) and anti-E was the most frequent Ab (52 cases; 69.3%). Packed RBC were predominantly involved (233 cases; 97,1%). Absolute imputability could be established in 120 cases only (50.0%). Previous transfusion history was observed in 85 F patients (56.7%) and 52M (57.8%). Pretransfusion Ab was noted in 18 F patients (12.0%) and five M (5.6%). Seventy-three F patients (48.7%) had had a pregnancy but the number of unknown data was high (71 F patients; 47.3%).

CONCLUSION

In the transfused patient population aged 80 and over, RBC Ab are common and in most cases are due to RBC transfusions. On the contrary, pretransfusion RBC Ab are not frequent.

Receipt of older RBCs does not predispose D-negative recipients to anti-D alloimmunization

The effect of the age of RBCs on anti-RBC alloimmunization has not been investigated in previous studies of the RBC storage lesion. D-negative recipients of at least 1 D-positive RBC unit were identified. Responders produced an anti-D, while nonresponders had not made anti-D when the database was searched. The 2 groups were matched for age, sex, length of serologic follow-up, and hospital location. There were 29 responders and 58 nonresponders. The median number of all RBCs transfused to the responders was 6, vs 10 for the nonresponders (P < .01); the median age of the RBCs was 15 vs 14 days, respectively (P = .70). Responders received a median of 3 D-positive RBC units vs 4 D-positive RBCs for nonresponders (P = .02); median ages of the D-positive RBCs were 16 vs 14 days, respectively (P = .21). There was no association between the age of transfused RBCs and the likelihood of anti-D alloimmunization.

Immune hemolytic anemia: a report of two cases

The transfusion-medicine specialists and physicians are often in a difficult situation when the patient has severe worsening anemia and all the blood is mismatched. This situation can arise in patients with red cell autoantibodies or alloantibodies due to previous transfusions. We report two cases of immune hemolysis – one due to warm auto antibodies and the second due to alloimmunization from multiple transfusions.