Red blood cell alloimmunization in transfused patients in sub-Saharan Africa: A systematic review and meta-analysis

Magnitude of Red Blood Cell Alloimmunization Among Pregnant Women Attending Antenatal Care at Wolaita Sodo University Comprehensive Specialized Hospital, Southwest Ethiopia

Background

Maternal red cell alloimmunization occurs when a woman's immune system becomes sensitive to unfamiliar red blood cell antigens. This leads to the production of alloantibodies, which can have serious implications for the fetus and newborn. However, there is a lack of comprehensive information about the extent of red cell alloimmunization in underdeveloped countries like Ethiopia. Therefore, this study aimed to determine the magnitude of red cell alloimmunization among pregnant women attending antenatal care at Wolaita Sodo University Comprehensive Specialized Hospital from September 01 to November 30, 2022.

Methods

In this institutional-based cross-sectional study, 422 pregnant women were participated and recruited using a systematic random sampling technique. Data on sociodemographic characteristics, obstetric history, and other clinical information were collected using structured questionnaires through face-to-face interview. Blood grouping and indirect antihuman globulin tests were performed. The relationship between red cell alloimmunization and the independent variables was determined using the chi-square test. P-value <0.05 was considered statistical significance.

Results

In this study, the blood group distributions among the participants were as follows: O, 177 (41.9%); A, 124 (29.4%); B, 76 (18%); and AB, 45 (3.86%). Among the pregnant women included in the study, a total of 51 (12.08%) were identified as RhD-negative. Out of these RhD-negative women, 5 (9.8%) were found to have developed alloimmunization with red blood cell antigens. Miscarriage and post-partum hemorrhage were found to be important factors associated with the occurrence of red cell alloimmunization in these women.

Conclusion

This study showed that one out of ten pregnant women was alloimmunized. Therefore, antenatal blood grouping and indirect antihuman globulin screening should be performed routinely to manage and minimize the undesirable outcomes of alloimmunization during pregnancy.

Feasibility and performance of in-house red blood cell reagents to detect unexpected antibodies in immunized patients in Burkina Faso

In sub-Saharan Africa, antibody detection tests remain inaccessible because of the high cost and limited shelf life of red blood cell (RBC) reagents. This study aimed at investigating the feasibility and performance of locally prepared RBC reagents for antibody detection in Burkina Faso. We conducted an experimental study comparing commercial RBC panels and a local panel prepared from phenotyped blood donors in Ouagadougou, Burkina Faso. Antibody detection testing was performed by the indirect antiglobulin test using a gel card filtration column in a low-ionic-strength solution. Judgment criteria were the concordance rate and the kappa agreement coefficient of results generated by the two panels. A total of 302 blood donors were phenotyped for the major antigens of the RH, KEL, MNS, FY, JK, LE, and P1PK blood group systems. From this pool of donors, we designed an RBC detection panel that was used to screen for unexpected antibodies in 1096 plasma samples from 832 patients with a history of transfusion and 264 recently delivered or pregnant women with no history of blood transfusion. A positive antibody detection test was observed in 8.1 percent of the samples using the local panel versus 6.4 percent with the commercial panels. A total of 23 samples were negative with the commercial panels and positive with the local panel, while the findings were reversed for four samples. The concordance rate was 97.5 percent, and the kappa agreement coefficient was 0.815. Our results suggest that the development of local RBC panels can be an alternative to commercial panels in countries with limited resources. It could also be a cost-effective intervention, mainly for children under 5 years of age, women of childbearing age, and pregnant women, all of whom are most at risk for malaria and sickle cell disease complications. Blood services could develop and implement appropriate strategies to make phenotyped donor pools available for the design of suitable RBC panels.

Prevalence and determinants of RH alloimmunization in Rh-negative women in teaching hospitals of Addis Ababa, Ethiopia: a hospital-based cross-sectional study

Background

Despite the implementation of immunization with an anti-D antigen for pregnant women, adverse pregnancy outcomes continue to occur in Ethiopia and most Sub-Saharan African countries. Consequently, the woman's obstetric care is compromised, and there is an increase in perinatal morbidity and mortality. In Ethiopia, the burden of the disease is not well understood, and no research has been conducted in the study area. Therefore, this study aims to determine the prevalence and determinants of Rh alloimmunization in Rh-negative women receiving care at Addis Ababa teaching hospitals.

Methods

An institutional-based cross-sectional study was conducted from 5 October 2020 to 5 May 2021, among 328 Rh-negative pregnant women who received antenatal care and delivery services at Teaching Hospitals under Addis Ababa University. Face-to-face interviews were used to gather data using a pre-tested structured questionnaire, and a chart review was performed using a checklist. The data were entered into Epidata version 3.1 and analyzed using SPSS version 22. Multivariable analysis and logistic regression were used to evaluate the predictors, and the results were presented as an adjusted odds ratio (AOR) with a 95% confidence interval. Statistical significance was declared at a p-value < 0.05.

Results

Among Rh-D negative individuals, 56(17.1%) were alloimunized with 95% CI (15.1%, 19.23%). The prevalence of Rh-D negative was 2.1% with 95% CI (1.56%, 2.76%). Factors such as unemployment [AOR = 2.28, 95% CI: 1.21, 4.28], failure to use anti-D prophylaxis in previous pregnancy [AOR = 2.08, 95% CI: 1.10, 3.92), and the presence of sensitizing events [AOR = 0.52, 95% CI: 0.27, 0.84] were statistically significant with the outcome variables.

Conclusions

This study pointed out that the prevalence of Rh was relatively large and that almost one in every five pregnant women was alloimunized. Factors such as unemployment and failure to use anti-D prophylaxis in a previous pregnancy were found to be associated with outcome variables. Therefore, all stakeholders and concerned entities should prioritize enhancing access and affordability to anti-D prophylaxis to prevent the occurrence of Rh alloimmunization and its associated adverse outcomes.

Comparison of the conventional tube and erythrocyte-magnetized technology in titration of red blood cell alloantibodies

BACKGROUND

Erythrocyte alloantibodies are mainly produced after immune stimulation, such as blood transfusion, pregnancy, and transplantation, and are the leading causes of severe hemolytic transfusion reactions and difficulty in blood grouping and matching. Therefore, antibody screening is critical to prevent and improve red cell alloantibodies. Routine tube assay is the primary detection method of antibody screening. Recently, erythrocyte-magnetized technology (EMT) has been increasingly used in clinical practice. This study intends to probe the application and efficacy of the conventional tube and EMT in red blood cell alloantibody titration to provide a reference for clinical blood transfusion.

AIM

To investigate the application value of conventional tube and EMT in red blood cell alloantibody titration and enhance the safety of blood transfusion practice.

METHODS

A total of 1298 blood samples were harvested from blood donors at the Department of Blood Transfusion of our hospital from March 2021 to December 2022. A 5 mL blood sample was collected in tubing, which was then cut, and the whole blood was put into a test tube for centrifugation to separate the serum. Different red blood cell blood group antibody titers were simultaneously detected using the tube polybrene test, tube antiglobulin test (AGT), and EMT screening irregular antibody methods to determine the best test method.

RESULTS

Simultaneous detection was performed through the tube polybrene test, tube AGT and EMT screening irregular antibodies. It was discovered that the EMT screening irregular antibody method could detect all immunoglobulin G (IgG) and immunoglobulin M (IgM) irregular antibodies, and the results of manual tube AGT were satisfactory, but the operation time was lengthy, and the equipment had a large footprint. The EMT screening irregular antibody assay was also conducted to determine its activity against type O Rh (D) red blood cells, and the outcomes were satisfactory. Furthermore, compared to the conventional tube method, the EMT screening irregular antibody method was more cost-effective and had significantly higher detection efficiency.

CONCLUSION

With a higher detection rate, the EMT screening irregular antibody method can detect both IgG and IgM irregular antibodies faster and more effectively than the conventional tube method.

Red blood cell alloantibodies in paediatric transfusion in sub-Saharan Africa: A new cohort and literature review

Blood transfusion support predisposes transfused children to the risk of erythrocyte alloimmunization in Sub-Saharan Africa. A cohort of 100 children receiving one to five blood transfusions were recruited for screening and identification of irregular antibodies using gel filtration technique. The mean age was 8 years and the sex-ratio at 1.2. The retrieved pathologies were: major sickle cell anaemia (46%), severe malaria (20%), haemolytic anaemia (4%), severe acute malnutrition (6%), acute gastroenteritis (5%), chronic infectious syndrome (12%) and congenital heart disease (7%). The children presented with haemoglobin levels ≤6 g/dl, and 16% of them presented positive irregular antibodies directed against the Rhesus (30.76%) and Kell (69.24%) blood group systems. A literature review shows that irregular antibody screenings vary from 17% to 30% of transfused paediatric patients in Sub-Saharan Africa. These alloantibodies are in particular directed against the Rhesus, Kell, Duffy, Kidd and MNS blood group and generally found in sickle cell disease and malaria. This study highlights the urgent need of extended red blood cell phenotyping including typing for C/c, E/e, K/k, and Fya/Fyb, and if possible Jka/Jkb, M/N, and S/s for children before transfusion in Sub-Saharan Africa.

Prevalence and specificity of red blood cell antibodies in patients transfused in tertiary hospitals in Burkina Faso

BACKGROUND

Sub-Saharan African countries face the challenge of immunological transfusion safety that puts many patients at risk of post-transfusion hemolytic reactions. This is because pre-transfusion testing for irregular/unexpected antibodies that helps to prevent these risks are neither universally available nor accessible. The aim of our study was to determine the prevalence of red blood cell alloantibodies and their specificity in patients transfused in Burkina Faso.

MATERIALS AND METHODS

This was a cross-sectional study including patients who had received at least one blood transfusion. Indirect antiglobulin testing using LISS-enhanced medium gel column agglutination technique was used for antibodies screening and identification. Enzymatic technique with papain-treated red cell reagent was performed in attempt to solve some difficulties if necessary as well as auto-control test and RH-KEL phenotyping when possible to help antibodies identification.

RESULTS

A total of 832 patients were included, 51.6% of whom were female, and the median (IQR) age was 34 (20-49) years. Of these, 43.7% had chronic kidney disease and 20.4% were sickle cell patients. The median (IQR) number of immunisation episodes (blood transfusion and pregnancies) was 3 (2-6) with the median (IQR) number of blood units received per patient of 2 (1-5). The proportion of patients with RBCs antibodies was 6.4% (53/832), with mainly anti-Rh antibodies. A combination of 2 antibodies was found in 7 patients and a combination of 3 antibodies in one patient. Antibodies of unknown specificity (AUS) were encountered in 29%. Independent factors associated with antibody positivity were age (OR = 1.02; p = 0.026), sickle cell disease (OR = 3.23; p = 0.017) and receiving more than 10 blood units (OR = 7.33; p = 0.01).

CONCLUSION

In this study, the proportion of patients with RBC antibodies was quite similar to that observed in Sub-Saharan African countries. However, the availability and accessibility of pre-transfusion compatibility tests as well as the quality of methods used should be improved to ensure the safety of blood transfusions.

Red blood cell alloimmunisation in multi-transfused patients with chronic renal failure undergoing haemodialysis in Ouagadougou, Burkina Faso, 2018

Background

In Burkina Faso, red blood cell (RBC) transfusion remains the crucial anaemia treatment following chronic renal failure (CRF) as erythropoietin and its analogues are unavailable. However, blood group matching beyond the ABO and Rhesus is not common in Burkina Faso. Thus, alloimmunisation is a potential issue for transfused patients.

Objective

Our study aimed to identify anti-erythrocyte antibodies in multi-transfused CRF patients at the Yalgado Ouedraogo Teaching Hospital, Ouagadougou, Burkina Faso.

Methods

This cross-sectional study, conducted from October 2018 to November 2019, included CRF patients who had received at least two RBC units. We screened patients for the presence of RBC antibodies using three commercial Cells panels and identified antibody specificities for positive screenings using 11 Cells panels for an indirect antiglobulin test (IAT) in a low ionic strength microcolumn gel-card system.

Results

Two hundred and thirty-five patients (45.1% female; average age: 41.5 years) were included. The median number of blood units received per patient was 10 (interquartile range: 5–20). The overall alloimmunisation rate was 5.9% (14/235). Antibodies identified included: anti-D (1 case), anti-C (1 case), anti-D+C (4 cases), anti-C^W (1 case), anti-E (1 case), anti-S (1 case) and anti-Le^a (1 case). In four positive patients, the specificity of the antibodies was indeterminate. No risk factors were associated with alloimmunisation.

Conclusion

In Burkina Faso, screening for RBC alloantibodies should be mandated for patients at risk. The high rate of indeterminate antibodies suggests the need to develop a local RBC antibody panel adapted to the local population.

Stroke Prevention with Hydroxyurea Enabled through Research and Education: A Phase 2 Primary Stroke Prevention Trial in Sub-Saharan Africa

INTRODUCTION

Stroke is a severe complication of sickle cell anemia (SCA), with devastating sequelae. Transcranial Doppler (TCD) ultrasonography predicts stroke risk, but implementing TCD screening with suitable treatment for primary stroke prevention in low-resource environments remains challenging. SPHERE (NCT03948867) is a prospective phase 2 open-label hydroxyurea trial for SCA in Tanzania.

METHODS

After formal training and certification, local personnel screened children 2-16 years old; those with conditional (170-199 cm/s) or abnormal (≥200 cm/s) time-averaged mean velocities (TAMVs) received hydroxyurea at 20 mg/kg/day with dose escalation to maximum tolerated dose (MTD). The primary study endpoint is change in TAMV after 12 months of hydroxyurea; secondary endpoints include SCA-related clinical events, splenic volume and function, renal function, infections, hydroxyurea pharmacokinetics, and genetic modifiers.

RESULTS

Between April 2019 and April 2020, 202 children (average 6.8 ± 3.5 years, 53% female) enrolled and underwent TCD screening; 196 were deemed eligible by DNA testing. Most had numerous previous hospitalizations and transfusions, with low baseline hemoglobin (7.7 ± 1.1 g/dL) and %HbF (9.3 ± 5.4%). Palpable splenomegaly was present at enrollment in 49 (25%); average sonographic splenic volume was 103 mL (range 8-1,045 mL). TCD screening identified 22% conditional and 2% abnormal velocities, with hydroxyurea treatment initiated in 96% (45/47) eligible children.

CONCLUSION

SPHERE has built local capacity with high-quality research infrastructure and TCD screening for SCA in Tanzania. Fully enrolled participants have a high prevalence of elevated baseline TCD velocities and splenomegaly. SPHERE will prospectively determine the benefits of hydroxyurea at MTD for primary stroke prevention, anticipating expanded access to hydroxyurea treatment across Tanzania.

Red blood cell alloimmunization among recipients of blood transfusion in India: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

There is a varied prevalence of red cell alloimmunization being reported from different parts of India. This study aimed to estimate the overall prevalence of alloimmunization in India by performing a systematic review of the literature and to establish the most suitable antigen-matching strategy to reduce the red blood cell (RBC) alloimmunization rate among transfusion recipients.

MATERIALS AND METHODS

A systematic search of all the original articles published in English on RBC alloimmunization among transfusion recipients from India in MEDLINE, SCOPUS, CINAHL and Google Scholar bibliographic databases was conducted. After screening the articles as per inclusion/exclusion criteria, data extraction was done independently by two sets of investigators. Meta-analysis was performed by the binary random-effects model using the restricted maximum likelihood method.

RESULTS

A total of 44 studies on RBC alloimmunization, with a cumulative sample size of 309,986 patients, were grouped into hospital-based and multiply-transfused patients, which yielded a prevalence of 0.5 (95% confidence interval; 0.3-0.8) and 4.8 (95% confidence interval; 3.9-5.7) per 100 patients, respectively. As many as 1992 alloantibodies were identified among the 1846 alloimmunized patients. The most common antibody identified was anti-E (127; 31.99%), followed by anti-c (75; 18.89%) in multiply-transfused patients.

CONCLUSION

The rate of alloimmunization was 0.5 per 100 patients tested for antibodies and 4.8 per 100 patients receiving transfusion. Considering E- and c-antigen-matched red cells along with ABO and RhD matching may significantly reduce the overall occurrence of alloimmunization among Indian population who are transfusion-dependent.

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.

Rapidly freeze-dried human red blood cells for pre-transfusion alloantibody testing reagents

Prior to transfusion of red blood cells (RBCs), recipients must be tested for the presence of alloantibodies to avoid immune complications. Liquid-preserved reagent RBCs with known blood group antigen phenotypes are used for testing. However, these reagents have practical constraints, including limited shelf-life and require constant refrigeration. To address these issues, we explore the effects of rapid freeze-drying conditions with trehalose cryoprotectant (0.1-1 M concentrations) on human RBCs and storage of freeze-dried RBCs (FDRBCs) at room temperature (RT) for up to 12 months. We report that rapid freeze-drying of RBCs for 2.5 hr with 0.5 M trehalose achieves recoverable cells with near-normal morphological shape, although size-reduced. The FDRBCs are metabolically active and functional in antibody-agglutination tests by the column agglutination test (CAT) for ABO and Rhesus-D blood group antigens. Expression of the Duffy blood group protein (CD234) decreases by 50% after freeze-drying RBCs. The initial recovery rate is ≤25%; however, 43% of these FDRBCs are still recoverable after RT storage for 12 months. In this proof-of-principle study, we show that rapid freeze-drying can stabilize RBCs. Further refinements to improve the recovery rate and preservation of antigenic epitopes will make FDRBCs a practical alternative source of reagent RBCs for pre-transfusion alloantibody identification.

Erythrocyte Alloimmunity and Genetic Variance: Results from the Collaborative Study of Alloimmunity to Antigen Diversity in Asian Populations (All ADP)

As an East-Asian international study, we evaluated erythrocyte alloimmunity by gender and history of transfusion or pregnancy. In total, data from more than 1,826,000 patients were analyzed, from whom 26,170 irregular erythrocyte antibodies were detected in 22,653 cases. Antibody frequencies in these cases were as follows: anti-E, 26.8%; anti-Le^a, 20.0%; anti-P1, 7.1%; anti-M, 6.4%; anti-Mi^a, 5.6%; anti-c + E, 5.6%; anti-Le^b, 4.6%; anti-D, 2.8%; anti-Fy^b, 2.6%; anti-Le^a+Le^b, 2.5%; anti-Di^a, 2.0%; and others. For pregnant patients, anti-D (12.7%) was statistically more frequent. For transfused patients, anti-E (37.3%), anti-c + E (9.5%), anti-C + e (3.3%) and anti-Jk^a (3.1%) were significantly more frequent.

Transfusion-Related Alloimmunization to Red Blood Cell Antigens in Japanese Pediatric Recipients

Red blood cell (RBC) transfusion to neonates is thought to rarely provoke an immune response. Neonatal testing guidelines suggest that antibody screening is not necessary when the mother has no antibodies. Alternatively, maternal blood samples can be used for antibody screening and cross-matching. However, the guidelines are based on small-scale studies of white-dominant populations. Furthermore, transfusion-related alloimmunization is less well established among children and adolescents as a whole among Japanese and East Asians. To elucidate the incidence of transfusion-related alloimmunization among neonates, children, and adolescents, and whether current guidelines are applicable to Japanese populations, a nationwide retrospective multicenter cohort survey was conducted in 50 tertiary-care hospitals in Japan. Between 2001 and 2015 inclusive, recipients of at least 1 allogeneic RBC transfusion were categorized into groups A-F according to their age at the time of transfusion: (A) neonates <1 month; (B) infants 1 to <12 months; (C) children 1 to <5 years; (D) prepubescents 5 to <10 years; (E) young pubescents 10 to <15 years; and (F) adolescents/young adults 15 to <20 years. Excluding maternally derived antibodies and naturally occurring, cold-reactive, and/or nonspecific antibodies, 69 (0.61%) of 11350 RBC recipients <20 years old formed at least 1 clinically significant alloantibody. The alloimmunization rate differed significantly (P < .0001) by age: none (0%) of 3407 in group A; 11 (0.46%) of 2410 in group B; 18 (0.76%) of 2361 in group C; 9 (0.80%) of 1119 in group D; 12 (1.15%) of 1043 in group E; and 19 (1.88%) of 1010 in group F. Clearly different incidences of alloimmunization emerged in group A compared to B, C, D, E, or F, as confirmed by logistic regression analysis adjusted by numbers of donor exposure. Alloimmunization did not occur from RBC transfusions within the first month of life and rarely occurred (0.46%-0.80%) after transfusion within the first decade of life. Alloimmunization occurred in 1.15%-1.88% of young pubescents and adolescents/young adults. These findings support the use of guidelines developed in Europe and the United States for East Asian pediatric recipients.

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

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

Transfusion Support of Minority Patients: Extended Antigen Donor Typing and Recruitment of Minority Blood Donors

One of the most important and persistent complications of blood transfusion is red blood cell (RBC) alloimmunization. When a patient is exposed to RBC antigens that differ from their own they can form alloantibodies to these foreign antigens. Blood group antigens are highly conserved and follow ancestral patterns of inheritance that may demonstrate population restriction. Minority populations who require chronic transfusion are at particularly high risk of alloimmunization when the blood donor population does not share the same ancestral background, resulting in exposure to non-self RBC antigens. It is incumbent on blood collectors to support patients with risk factors for alloimmunization as well as patients who have already formed alloantibodies. Increasing utilization of RBC genotyping may represent an opportunity to improve access to RBC units from donors that match the extended RBC phenotype of all possible patients.

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.

Efficacy and Safety of Manual Partial Red Cell Exchange in the Management of Severe Complications of Sickle Cell Disease in a Developing Country

Introduction

The realization of red cell exchange (RCE) in Africa faces the lack of blood, transfusion safety, and equipment. We evaluated its efficacy and safety in severe complications of sickle cell disease.

Patients and Method

Manual partial RCE was performed among sickle cell patients who had severe complications. Efficacy was evaluated by clinical evolution, blood count, and electrophoresis of hemoglobin. Safety was evaluated on adverse effects, infections, and alloimmunization.

Results

We performed 166 partial RCE among 44 patients including 41 homozygous (SS) and 2 heterozygous composites SC and 1 S/β0-thalassemia. The mean age was 27.9 years. The sex ratio was 1.58. The regression of symptoms was complete in 100% of persistent vasoocclusive crisis and acute chest syndrome, 56.7% of intermittent priapism, and 30% of stroke. It was partial in 100% of leg ulcers and null in acute priapism. The mean variations of hemoglobin and hematocrit rate after one procedure were, respectively, +1.4 g/dL and +4.4%. That of hemoglobin S after 2 consecutive RCE was −60%. Neither alloimmunization nor viral seroconversion was observed.

Conclusion

This work shows the feasibility of manual partial RCE in a low-resource setting and its efficacy and safety during complications of SCD outside of acute priapism.

Delayed cord clamping in red blood cell alloimmunization: safe, effective, and free?

Hemolytic disease of the newborn (HDN), an alloimmune disorder due to maternal and fetal blood type incompatibility, is associated with fetal and neonatal complications related to red blood cell (RBC) hemolysis. After delivery, without placental clearance, neonatal hyperbilirubinemia may develop from ongoing maternal antibody-mediated RBC hemolysis. In cases refractory to intensive phototherapy treatment, exchange transfusions (ET) may be performed to prevent central nervous system damage by reducing circulating bilirubin levels and to replace antibody-coated red blood cells with antigen-negative RBCs. The risks and costs of treating HDN are significant, but appear to be decreased by delayed umbilical cord clamping at birth, a strategy that promotes placental transfusion to the newborn. Compared to immediate cord clamping (ICC), safe and beneficial short-term outcomes have been demonstrated in preterm and term neonates receiving delayed cord clamping (DCC), a practice that may potentially be effective in cases RBC alloimmunization.