Challenges of alloimmunization in patients with haemoglobinopathies

Predictors of Red Cell Alloimmunization in Multitransfused Egyptian Patients With β-Thalassemia

Context.—Thalassemia is a major health problem in Egypt. Red blood cell alloimmunization is an important complication in transfusion-dependent patients.

Objectives.—To determine alloimmunization prevalence in Egyptian patients with β-thalassemia and to evaluate risk factors that could influence alloimmunization, with the hope of minimizing transfusion-associated risks in those patients.

Design.—Records of 272 patients with β-thalassemia who are receiving regular blood transfusions, matched for ABO-Rh(D), were analyzed. Alloantibody identification was performed by DiaMed-ID microtyping system. Autoantibodies were detected by direct Coombs test.

Results.—Alloimmunization incidence was 22.8% with 123 alloantibodies detected in 62 patients. The most common alloantibody was Rh-related (37.4%; 46 of 123), comprising anti-E (14.6%; 18 of 123), anti-D (8.9%; 11 of 123), anti-C (8.9%; 11 of 123), and anti-c (4.9%; 6 of 123), followed by anti-Kell (26%; 32 of 123), → anti-MNS (9.8%; 12 of 123), → anti-Kidd (8.9%; 11 of 123) → anti-Duffy (8.1%; 10 of 123), → anti-Le (5.7%; 7 of 123), → anti-Lu (2.4%; 3 of 123), and → anti-P1 (1.6%; 2 of 123). Anti-D antibodies developed in 34.5% of all Rh-negative patients. Eighty percent of all anti-D antibodies developed in patients older than 18 years. Males had the highest alloimmunization incidence. Alloimmunization incidence increased with the number of units transfused (P = .01). Patients who received unfiltered blood had a higher alloimmunization rate than did those who always received leukoreduced blood (P < .001). Splenectomized patients had a higher alloimmunization rate (32%; 40 of 125) than did those who did not have a splenectomy (16.3%; 24 of 147; P = .003). Autoantibodies occurred in 1.5% (4 of 272) of all patients.

Conclusion.—Transfusion of leukoreduced and phenotypically matched cells for selective antigens may help reduce expenses and risks of alloimmunization in patients with thalassemia.

Is Next Generation Sequencing the future of blood group testing?

Blood group genotyping has many advantages over conventional phenotyping for both blood donors and patients, and a number of high-throughput methods have now been developed. However, these are limited by a requirement for existing knowledge of the relevant blood group gene polymorphisms, and rare or novel mutations will not be detected. These mutations could be successfully identified by DNA sequencing of the blood group genes, and such an approach has been made feasible by the introduction of Next Generation Sequencing (NGS) technology. NGS enables many genes from multiple samples to be sequenced in parallel, resulting in sequencing information that could be used to obtain accurate blood group phenotype predictions in both blood donors and patients.

Non-transfusion-dependent thalassemias

Non-transfusion-dependent thalassemias include a variety of phenotypes that, unlike patients with beta (β)-thalassemia major, do not require regular transfusion therapy for survival. The most commonly investigated forms are β-thalassemia intermedia, hemoglobin E/β-thalassemia, and α-thalassemia intermedia (hemoglobin H disease). However, transfusion-independence in such patients is not without side effects. Ineffective erythropoiesis and peripheral hemolysis, the hallmarks of disease process, lead to a variety of subsequent pathophysiologies including iron overload and hypercoagulability that ultimately lead to a number of serious clinical morbidities. Thus, prompt and accurate diagnosis of non-transfusion-dependent thalassemia is essential to ensure early intervention. Although several management options are currently available, the need to develop more novel therapeutics is justified by recent advances in our understanding of the mechanisms of disease. Such efforts require wide international collaboration, especially since non-transfusion-dependent thalassemias are no longer bound to low- and middle-income countries but have spread to large multiethnic cities in Europe and the Americas due to continued migration.

Trends in blood transfusion among hospitalized children with sickle cell disease

BACKGROUND

Blood transfusions represent a major therapeutic option in acute management of sickle cell disease (SCD). Few data exist documenting trends in transfusion among children with SCD, particularly during hospitalization.

PROCEDURE

This was an analysis of cross-sectional data of hospital discharges within the Kid's Inpatient Database (years 1997, 2000, 2003, 2006, 2009). Hospitalizations for children (0-18 years) with a primary or secondary SCD-related diagnosis were examined. The primary outcome was blood transfusion. Trends in transfusion were assessed using weighted multivariate logistic regression in a merged dataset with year as the primary independent variable. Co-variables consisted of child and hospital characteristics. Multivariate logistic regression was conducted for 2009 data to assess child and hospital-level factors associated with transfusion.

RESULTS

From 1997 to 2009, the percentage of SCD-related hospitalizations with transfusion increased from 14.2% to 28.8% (P < 0.0001). Among all SCD-related hospitalizations, the odds of transfusion increased over 20% for each successive study interval. Hospitalizations with vaso-occlusive pain crisis (OR 1.35, 95% CI 1.27-1.43) or acute chest syndrome/pneumonia (OR 1.24, 95% CI 1.13-1.35) as the primary diagnoses had the highest odds of transfusion for each consecutive study interval. Older age and male gender were associated with higher odds of transfusion.

CONCLUSIONS

Blood transfusion is increasing over time among hospitalized children with SCD. Further study is warranted to identify indications contributing to the rise in transfusions and if transfusions in the inpatient setting have been used appropriately. Future studies should also assess the impact of rising trends on morbidity, mortality, and other health-related outcomes.

Red blood cell alloimmunization in sickle cell disease and in thalassaemia: current status, future perspectives and potential role of molecular typing

Red blood cell (RBC) transfusions are a milestone in the treatment for sickle cell anaemia (SSA) and for thalassaemia. RBC alloimmunization remains a major challenge of chronic transfusion therapy, and it can lead to adverse life-threatening events. The alloimmunization risk could depend on multiple factors such as the number of transfusions and, most of all, the genetic background. Different ethnic groups are predisposed to immunization because of a significant degree of RBC antigenic mismatch between donor and recipient. There is no universal agreement and standards for the most appropriate selection of RBC units in chronically transfused subjects. Current practice only deals with compatibility of ABO, Rh and K antigens. Molecular RBC antigenic matching extended to other blood group systems is an innovative strategy to ensure a better quality and effectiveness of transfusion therapy.

High prevalence of red blood cell alloimmunization in sickle cell disease despite transfusion from Rh-matched minority donors

Rh serologic phenotype–matched transfusions from minority donors do not prevent all Rh alloimmunization in patients with SCD. Variant RH genes are common in patients with SCD and contribute to Rh alloimmunization and transfusion reactions.

Transfusion therapy for sickle cell disease: a balancing act

Transfusion therapy is a key intervention in decreasing morbidity and mortality in patients with sickle cell disease (SCD). Current indications for acute and chronic transfusion therapy have significantly increased the number of RBC units transfused to patients with SCD worldwide. This review summarizes transfusion management for the treatment or prevention of neurologic and perioperative complications, acute chest syndrome, and acute anemia associated with SCD. Despite the recognized benefits of transfusion therapy, it is not without the risks of iron overload, alloimmunization, and delayed hemolytic transfusion reactions. Transfusional iron overload management includes automated RBC exchange, noninvasive imaging to monitor iron burden, and iron chelation with parenteral or oral agents. Although limited and extended RBC antigen matching reduces antibody formation, the prevalence of RBC alloimmunization in patients with SCD remains high. Recent studies demonstrate that RH genetic diversity in patients with SCD contributes to Rh alloimmunization, suggesting that even more refined RBC matching strategies are needed. Advances in molecular blood group typing offer new opportunities to improve RBC matching of donors and recipients and can be of particular benefit to patients with SCD.