Sickle Cell Disease in Africa: SickleInAfrica Registry in Ghana, Nigeria and Tanzania

Introduction

Sickle cell disease (SCD) is most prevalent in Sub-Saharan Africa (SSA), where incomplete patient profiles and limited management strategies hinder research and healthcare standards.

Methods

We describe the first large-scale and multinational assessment of 13,403 SCD patients enrolled from 2017-2021 across 31 facilities in Ghana, Nigeria, and Tanzania into the SickleInAfrica consortium registry. We used hierarchical regression models to estimate and analyze the demographics, adoption levels of SCD diagnosis and therapies.

Results

The average age at diagnosis was 3 months, 19 months and 3 years in Ghana, Nigeria and Tanzania respectively, reflecting differences in country-specific newborn screening programs and policies. Hydroxyurea (HU) use was highest in Ghana (21%), followed by Nigeria (12%) and Tanzania (6%), with significant variability across facilities. Sex differences in SCD management were observed, with males more likely to receive HU and blood transfusions. At the consortium level, HU initiation correlated with enrolment age rather than age at diagnosis, highlighting the need for earlier intervention.

Conclusions

Our findings highlight the potential of the SickleInAfrica registry toward enhancing understanding of regional disparities in SCD care and potential gender inequalities, emphasizing the need for enabling policies toward strengthened SCD research and improved quality of life and care of patients in Africa.

Red blood cell extended antigen typing in Omani patients with sickle cell disease to enhance daily transfusion practice

Many Omani patients with sickle cell disease (SCD) undergo red blood cell (RBC) transfusions that are only matched for ABO and D, making RBC alloimmunization a significant concern in this population. Currently, the integration of molecular assays and hemagglutination testing helps to determine RBC phenotypes and genotypes, facilitating the provision of compatible blood and minimizing additional alloimmunization risks in patients with SCD. Based on this finding, our objective was to use molecular methods to predict the extended antigen profile of Omani patients with SCD across various blood group systems including Rh, Kell, Duffy, Kidd, Colton, Lutheran, Dombrock, Diego, Cartwright, and Scianna. This approach aims to implement RBC matching strategies and enhance daily transfusion practices for these patients. Molecular methods encompassed multiplex polymerase chain reaction for RHD, BeadChip arrays for variants of RHD and RHCE, and ID CORE XT for the primary allelic variants of RBCs. This study enrolled 38 patients with SCD, comprising 34 patients with homozygous HbSS, 1 patient with HbSC, and 3 patients with HbS Oman. The predominant ABO blood group was group O, observed in 44.7 percent of patients, followed by group A in 21.1 percent and group B in 13.2 percent. The most prevalent Rh phenotype predicted from the genotype was D+C+E-c+e+, identified in 34.2 percent of patients. All patient samples were K-, exhibiting the k+ Kp(b+) Js(b+) phenotype, with 81.6 percent demonstrating Fy(a-b-) due to the homozygous FY*02N.01 genotype and 28.9 percent displaying Jk(a+b-). RH variant alleles were detected in five patients (13.2 %), with only one type of RHD variant (RHD*DIIIa) and one type of RHCE variant (RHCE*ceVS.02.01) identified. Alloantibodies were present in 26 patients (68.4%). This study presents the initial comprehensive report of extended RBC antigen profiling in Omani patients with SCD, revealing disparities in the prevalence of RBC phenotypes compared with SCD patients from other regions and countries. Furthermore, our findings underscore a high rate of alloimmunization in these patients, emphasizing the need to implement antigen-matching programs to improve daily transfusion practices.

Investigation of Delayed Transfusion Reactions in Sickle Cell Disease Patients Polytransfused in the Brazilian Amazon

BACKGROUND

Sickle cell disease (SCD) affects approximately 100,000 people in the United States and millions worldwide, with the highest prevalence of 70% of SCD being found in individuals of African ethnicity. Delayed hemolytic, alloimmunization, and anamnestic transfusion reactions in multiple transfusion patients need to be investigated and managed to avoid a worsening of the patient's clinical status.

OBJECTIVE

This paper aims to investigate delayed transfusion reactions in SCD patients who were polytransfused in the Brazilian Amazon.

MATERIAL AND METHODS

The clinical and laboratory indicators of SCD patients with more than four transfusions were investigated. The patients were treated at the Fundação Hospitalar de Hematologia e Hemoterapia do Estado do Amazonas, Brazil.

RESULTS

A total of 44 polytransfused patients with SCD were followed. Regarding Rh phenotype, it was possible to observe a frequency of 26.6% (12) patients with the RZRZ (DCE/DCE) phenotype, in addition to 4.5% (two) patients with RH and RHCE variants. It was also possible to observe 20.5% (nine) patients with an alloimmunization reaction, who presented the following alloantibodies: anti-RhD, anti-E, anti-K, anti-Jkb, anti-N, anti-S, and anti-Dia, two of which are unidentified. Of these, four (44.4%) patients also presented autoantibodies, anti-e, and three unidentified antibodies, and four (44.4%) patients presented an anamnestic reaction, with anti-RhD, K, and Jkb antibodies. Of the 44 patients monitored, 54.4% (24) had clinical and laboratory indicators of a delayed hemolytic reaction.

CONCLUSION

Delayed transfusion reactions, often neglected, occur frequently. Therefore, transfusions need to be monitored for at least 28 days, with medical investigation of clinical and laboratory indicators to make greater use of this therapeutic resource.

Current challenges and new approaches to implementing optimal management of sickle cell disease in sub-Saharan Africa

Sickle cell disease (SCD) is the most common life-threatening monogenic disorder in the world. The disease is highly prevalent in malaria endemic areas with over 75% of patients residing in Sub-Saharan Africa (SSA). It is estimated that, without proper care, up to 90% of children with SCD will not celebrate their fifth birthday. Early identification and enrolment into comprehensive care has been shown to reduce the morbidity and mortality related with SCD complications. However, due to resource constraints, the SSA is yet to implement universal newborn screening programs for SCD. Furthermore, care for patients with SCD in the region is hampered by the shortage of qualified healthcare workers, lack of guidelines for the clinical management of SCD, limited infrastructure for inpatient and outpatient care, and limited access to blood and disease modifying drugs such as Hydroxyurea which contribute to poor clinical outcomes. Curative options such as bone marrow transplant and gene therapy are expensive and not available in many SSA countries. In addressing these challenges, various initiatives are ongoing in SSA which aim to enhance awareness on SCD, improve patient identification and retention to care, harmonize the standards of care for SCD, improve the skills of healthcare workers and conduct research on pertinent areas in SCD in the SSA context. Fortifying these measures is paramount to improving the outcomes of SCD in SSA.

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.

The use of pluripotent stem cells to generate diagnostic tools for transfusion medicine

Red blood cell (RBC) transfusion is one of the most common medical treatments, with more than 10 million units transfused per year in the United States alone. Alloimmunization to foreign Rh proteins (RhD and RhCE) on donor RBCs remains a challenge for transfusion effectiveness and safety. Alloantibody production disproportionately affects patients with sickle cell disease who frequently receive blood transfusions and exhibit high genetic diversity in the Rh blood group system. With hundreds of RH variants now known, precise identification of Rh antibody targets is hampered by the lack of appropriate reagent RBCs with uncommon Rh antigen phenotypes. Using a combination of human-induced pluripotent stem cell (iPSC) reprogramming and gene editing, we designed a renewable source of cells with unique Rh profiles to facilitate the identification of complex Rh antibodies. We engineered a very rare Rh null iPSC line lacking both RHD and RHCE. By targeting the AAVS1 safe harbor locus in this Rh null background, any combination of RHD or RHCE complementary DNAs could be reintroduced to generate RBCs that express specific Rh antigens such as RhD alone (designated D--), Goa+, or DAK+. The RBCs derived from these iPSCs (iRBCs) are compatible with standard laboratory assays used worldwide and can determine the precise specificity of Rh antibodies in patient plasma. Rh-engineered iRBCs can provide a readily accessible diagnostic tool and guide future efforts to produce an alternative source of rare RBCs for alloimmunized patients.

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.

Frequency of Extended Red Cell Antigen Phenotype Among Patients of Hematological Diseases: A Single Center Study

Background

Alloimmunization of erythrocytes is a major problem in patients with hematological diseases that require frequent blood transfusions. Matching of extended red cell antigens of Kell, MNS, Kidd, and Duffy can decrease the risk of alloimmunization. Hence, in this study, the frequencies of the extended red cell phenotypes were explored.

Objective

To find out the frequency of extended red blood cell antigen phenotypes among patients with hematological diseases.

Methods

This cross-sectional research study was performed on 488 patients diagnosed with hematological diseases who required blood transfusion at the National Institute of Blood Disease and Bone Marrow Transplantation Karachi for a period of 1.42 years from November 2019 to March 2021. The blood of patients was analyzed for antigen phenotypes of different blood group systems including Kell, MNS, Kidd, and Duffy. The data obtained were interpreted.

Results

Among the 488 patients, 284 (58.20%) patients were male, and 204 (41.80%) patients were female with a mean age of 8.1 years. Beta thalassemia was the most common hematological disease reported in 354 (72.5%) of the patients. The most common blood group was O positive reported in 182 (37.3%) of the patients followed by B positive blood group in 124 (25.4%). The frequencies of extended red cell antigen phenotypes in the patients were K antigen 14 (2.9%), Kp^a antigen 26 (5.3%), Kp^b antigen 424 (86.9%), Fy^a antigen 360 (73.8%), Fy^b antigen 260 (53.3%), Jk^a antigen 294 (60.2%), Jk^b antigen 326 (66.8%), M antigen 410 (84.0%) and N antigen 306 (62.7%).

Conclusion

Beta thalassemia was the most common hematological disease followed by iron deficiency anemia, aplastic anemia, and acute leukemia. Patients with hematological diseases had a higher prevalence of Kp^b antigen followed by M, Fy^a, Jk^b, N, Jk^a, Fy^b, Kp^a, and K antigen. O positive was the most frequent blood group followed by B positive, A positive and AB positive blood group.

High susceptibility to severe malaria among patients with A blood group versus those with O blood group: A cross-sectional study in the Democratic Republic of the Congo

This study aimed to assess the association of severe malaria infection with the ABO blood groups among acute febrile patients at the General Hospital of Rungu, in the Democratic Republic of the Congo. This cross-sectional study was conducted between August and October 2018. Plasmodium falciparum-infected individuals were categorized as severe malaria and uncomplicated malaria. A total of 400 febrile patients were enrolled. The majority (n = 251; 62.8%) was positive P. falciparum in microscopy test, of whom 180 (71.7%) had uncomplicated malaria and 71 (28.3%) severe malaria; 32.3%, 18.3%, 2.8%, and 46.6% were found to be blood group of A, B, AB, and O, respectively. In the multivariate analysis using the logistic regression models, severe malaria was high among patients with A blood group compared to those with O blood group (45.8% vs. 13.7%; adjusted odds ratio: 5.3 [95% confidence interval: 2.7–10.5]; P < 0.001). This survey demonstrates that patients with A blood group had a high susceptibility to severe malaria compared to those with O blood group.

Red cell transfusion and alloimmunization in sickle cell disease

Red cell transfusion remains a critical component of care for acute and chronic complications of sickle cell disease. Randomized clinical trials demonstrated the benefits of transfusion therapy for prevention of primary and secondary strokes and postoperative acute chest syndrome. Transfusion for splenic sequestration, acute chest syndrome, and acute stroke are guided by expert consensus recommendations. Despite overall improvements in blood inventory safety, adverse effects of transfusion are prevalent among patients with sickle cell disease and include alloimmunization, acute and delayed hemolytic transfusion reactions, and iron overload. Judicious use of red cell transfusions, optimization of red cell antigen matching, and the use of erythrocytapheresis and iron chelation can minimize adverse effects. Early recognition and management of hemolytic transfusion reactions can avert poor clinical outcomes. In this review, we discuss transfusion methods, indications, and complications in sickle cell disease with an emphasis on alloimmunization.

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.

An Analysis of Racial and Ethnic Backgrounds Within the CASiRe International Cohort of Sickle Cell Disease Patients: Implications for Disease Phenotype and Clinical Research

Millions are affected by sickle cell disease (SCD) worldwide with the greatest burden in sub-Saharan Africa. While its origin lies historically within the malaria belt, ongoing changes in migration patterns have shifted the burden of disease resulting in a global public health concern. We created the Consortium for the Advancement of Sickle Cell Research (CASiRe) to understand the different phenotypes of SCD across 4 countries (USA, UK, Italy, and Ghana). Here, we report the multi-generational ethnic and racial background of 877 SCD patients recruited in Ghana (n = 365, 41.6%), the USA (n = 254, 29%), Italy (n = 81, 9.2%), and the UK (n = 177, 20.2%). West Africa (including Benin Gulf) (N = 556, 63.4%) was the most common geographic region of origin, followed by North America (N = 184, 21%), Caribbean (N = 51, 5.8%), Europe (N = 27, 3.1%), Central Africa (N = 24, 2.7%), and West Africa (excluding Benin Gulf) (N = 21, 2.4%). SCD patients in Europe were primarily West African (73%), European (10%), Caribbean (8%), and Central African (8%). In the USA, patients were largely African American (71%), Caribbean (13%), or West African (10%). Most subjects identified themselves as Black or African American; the European cohort had the largest group of Caucasian SCD patients (8%), including 21% of the Italian patients. This is the first report of a comprehensive analysis of ethnicity within an international, transcontinental group of SCD patients. The diverse ethnic backgrounds observed in our cohort raises the possibility that genetic and environmental heterogeneity within each SCD population subgroup can affect the clinical phenotype and research outcomes.

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.