Red blood cell alloimmunization in transfused patients with bone marrow failure syndromes

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

OBJECTIVE

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

DATA SOURCES

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

METHODS OF STUDY SELECTION

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

TABULATION, INTEGRATION, AND RESULTS

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

CONCLUSION

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

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42023411620 .

Increased red blood cell alloimmunization rates in transfused aplastic anemia and myelofibrosis patients

BACKGROUND

Red blood cell (RBC) alloimmunization (AI) is a well-known complication of RBC transfusions, which results in the formation of alloantibodies to non-self antigens on donor RBCs, putting patients at risk of transfusion-related complications. The rate of AI with RBC transfusions in the general hospitalized population is estimated to be 2%-3%. However, some patients who are deemed "transfusion-dependent" require regular transfusions of blood products due to persistently low cell counts, putting them at even greater risk of RBC AI and increased morbidity. However, few studies currently exist investigating RBC AI in some transfusion-dependent patient populations, e.g., aplastic anemia (AA) and myelofibrosis (MF).

STUDY DESIGN AND METHODS

We conducted a 5-year retrospective review to investigate the prevalence of RBC AI, alloantibody incidence, and the number of RBC transfusions in AA and MF patients, who received RBC transfusions within our hospital system.

RESULTS

During the study period, 64 AA and 93 MF patients received 1301 and 2766 RBC transfusions, respectively. Compared to the RBC AI rate in the generalized hospitalized patient population (1%-2%), patients with AA and MF had an increased rate of RBC AI incidence rate at 14.1% and 12.9%, respectively. Furthermore, patients with primary MF demonstrated an isolated increased RBC AI incidence rate of 13.3%. The most common alloantibodies produced were anti-E and anti-K.

DISCUSSION

Within our institution, patients with AA and MF had increased incidence rates of RBC AI compared to the general hospitalized patient population and may benefit from an antigen-matched protocol to minimize AI-related complications.

The Development and Consequences of Red Blood Cell Alloimmunization

While red blood cell (RBC) transfusion is the most common medical intervention in hospitalized patients, as with any therapeutic, it is not without risk. Allogeneic RBC exposure can result in recipient alloimmunization, which can limit the availability of compatible RBCs for future transfusions and increase the risk of transfusion complications. Despite these challenges and the discovery of RBC alloantigens more than a century ago, relatively little has historically been known regarding the immune factors that regulate RBC alloantibody formation. Through recent epidemiological approaches, in vitro-based translational studies, and newly developed preclinical models, the processes that govern RBC alloimmunization have emerged as more complex and intriguing than previously appreciated. Although common alloimmunization mechanisms exist, distinct immune pathways can be engaged, depending on the target alloantigen involved. Despite this complexity, key themes are beginning to emerge that may provide promising approaches to not only actively prevent but also possibly alleviate the most severe complications of RBC alloimmunization.

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

BACKGROUND

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

STUDY DESIGN AND METHODS

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

RESULTS

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

CONCLUSION

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

Association between ABO Blood Group and Risk of Congenital Heart Disease: A 6-year large cohort study

ABO blood group, except its direct clinical implications for transfusion and organ transplantation, is generally accepted as an effect factor for coronary heart disease, but the associations between ABO blood group and congenital heart disease (CHD) are not coherent by previous reports. In this study, we evaluated the the potential relationship between ABO blood group and CHD risk. In 39,042 consecutive inpatients (19,795 CHD VS 19,247 controls), we used multivariable logistic regression to evaluate the roles of ABO blood group, gender, and RH for CHD. The associations between ABO blood group and CHD subgroups, were further evaluated using stratification analysis, adjusted by gender. A blood group demonstrated decreased risk for isolated CHD (OR 0.82; 95% CI, 0.78–0.87) in individuals with A blood group in the overall cohort analysis, and the finding was consistently replicated in independent subgroup analysis. ABO blood group may have a role for CHD, and this novel finding provides ABO blood group as a possible marker for CHD, but more studies need to be done.