Background and objectives
To date, it is unclear whether antigen matching is effective in reducing antibody development and whether transfusing blood from non‐Caucasian donors reduces alloimmunization in sickle cell disease patients (SCP). This study was designed to evaluate the effectiveness of an antigen‐matching strategy supplied by a mixed donor population, in reducing alloimmunization in SCPs.
Methods
Eighty SCPs transfused with C‐, E‐ and K‐matched units and 2000 donors were genotyped for the most relevant RBC antigens, and resulting genotypic frequencies were compared. Also, alloantibodies specificity and clinical complications were evaluated in SCPs.
Results
A high alloimmunization rate was observed despite the prophylaxis protocol (62·1%). The main cause underlying lack of effectiveness was transfusion of non‐matched units in external hospitals. Even though our donor population was ethnically mixed, it still exhibited antigenic differences in relation to SCPs (C and Fya). Frequency of clinical complications was similar between alloimmunized and non‐alloimmunized patients.
Conclusions
Prospective antigen matching is an unattractive alloimmunization prophylaxis for SCPs if not associated with strategies to minimize the hazards related to transfusions at non‐index hospitals. Even in a highly mixed donor population, antigenic discrepancies in SCPs are high, increasing the risk of antibody development.
Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) molecule is expressed on T-lymphocyte membrane and negatively influences the antigen-presenting process. Reduced expression of CTLA-4 due to gene polymorphisms is associated with increased risk of autoimmune disorders, whose physiopathology is similar to that of post-transfusion red blood cell (RBC) alloimmunization. Our goal was to evaluate if polymorphisms of CTLA-4 gene that affect protein expression are associated with RBC alloimmunization. This was a case-control study in which 134 sickle cell disease (SCD) patients and 253 non-SCD patients were included. All patients were genotyped for the polymorphisms 49A/G and -318C/T of CTLA-4 gene. The genotype frequency of -318C/T differed significantly between alloimmunized and nonalloimmunized SCD patients, irrespective of clinical confounders (p = .016). SCD patients heterozygous for -318T allele presented higher risk of alloantibody development (OR: 5.4, CI: 1.15-25.6). In conclusion, the polymorphism -318C/T of CTLA-4 gene is associated with RBC alloimmunization among SCD patients. This highlights the role played by CTLA-4 on post-transfusion alloantibody development.
ObjectiveBrazilian legislation has recently suggested the use of the qualitative hemolysin test instead of isohemagglutinin titers as prophylaxis for acute hemolysis related to plasma-incompatible platelet transfusions. The efficacy of this test in preventing hemolytic reactions has never been evaluated while isohemagglutinin titers have been extensively studied. The main objective of this study was to evaluate the correlation between the results of these two tests. The impact of each type of prophylaxis on the platelet inventory management and the ability of the qualitative hemolysin test to prevent red cell sensitization after the transfusion of incompatible units were also studied.MethodsA total of 246 donor blood samples were evaluated using both isohemagglutinin titers and the qualitative hemolysin test, and the results were statistically compared. Subsequently, 600 platelet units were tested using the hemolysin assay and the percentage of units unsuitable for transfusion was compared to historical data using isohemagglutinin titers (cut-off: 100). Moreover, ten patients who received units with minor ABO incompatibilities that were negative for hemolysis according to the qualitative hemolysin test were evaluated regarding the development of hemolysis and red cell sensitization (anti-A or anti-B).ResultsIsohemagglutinin titration and the results of qualitative hemolysin test did not correlate. The routine implementation of the qualitative hemolysin test significantly increased the percentage of platelet units found unsuitable for transfusions (15–65%; p-value <0.001). Furthermore the qualitative hemolysin test did not prevent red blood cell sensitization in a small exploratory analysis.ConclusionQualitative hemolysin test results do not correlate to those of isohemagglutinin titers and its implementation as the prophylaxis of choice for hemolysis associated with plasma-incompatible platelet transfusions lacks clinical support of safety and significantly affects platelet inventory management.
The strategy of checking D- donors with RHD PCR followed by exclusion of RHD*Ψ allele has proved efficient in identifying weak-D and DEL phenotype in the Brazilian population.
MMA can be used to evaluate the ability of RBC autoantibodies to mediate overt hemolysis. It can be especially useful to determine the role played by cold and warm auto-antibodies in mixed auto-immune hemolytic disease, helping to define the best treatment option.
Background High-throughput molecular assays are essential tools for the search of rare blood donors.Aims and methods To evaluate a fully automated workflow designed for genotyping blood donors' red blood cell (RBC) and platelets (PTL) antigens using the OpenArray Real-time PCR system.Results 5487 blood donors were genotyped using the proposed strategy in two steps: (1) nucleic acid purification in the QIASymphony â equipment and (2) genotyping of the most important RBC and PTL antigens by a customized assay designed for the OpenArray Real-time PCR system. 142 662 single nucleotide polymorphisms were genotyped with 99Á6% of accuracy in 15 work-days. Software was created for the purpose of data interfacing and organization of a database to be used in a regular basis to find compatible blood for alloimmunized patients.
ConclusionsThe proposed fully automated genotyping strategy is accurate, fast and suitable for meeting the needs of a laboratory of molecular immunohematology.
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