Background/Objectives: Red blood cell (RBC) alloimmunization is a significant challenge in transfusion medicine, particularly among transfusion-dependent patients, such as those with thalassemia. It arises from the production of antibodies against non-self RBC antigens and can lead to complications like hemolytic transfusion reactions. This study aimed to evaluate the prevalence, specificity, and clinical implications of RBC alloimmunization at the University Clinical Center of Serbia (UCCS), emphasizing transfusion-dependent populations. Methods: This retrospective study analyzed 27,530 transfusion records at UCCS between January 2023 and January 2024. Pre-transfusion testing included ABO and RhD typing, irregular antibody screening, and crossmatching. Data from 630 patients with positive antibody screening were reviewed. Alloantibody specificity was determined using indirect antiglobulin tests and advanced phenotyping methods. Results: Among 27,530 patients, 630 (2.29%) tested positive for irregular antibodies, predominantly males (57.14%) with a mean age of 49.6 years. Alloantibodies were detected in 70.47% of cases, most commonly targeting Rh (53.35%) and Kell (17.15%) systems. Anti-E (27.93%) and anti-D (18.02%) were the most frequent antibodies. Multiple alloantibodies were identified in 18.41% of patients, posing challenges for blood compatibility. In a total of 495 patients with thalassemia, antibodies were found in 9.69%. Alloimmunization was significantly associated with higher numbers of transfusions and pregnancies (p < 0.05). Conclusions: Our findings indicate that alloimmunization is predominantly associated with Rh and Kell antigens, suggesting that implementing targeted antigen matching may reduce the frequency of alloimmunization. While our study does not directly assess the impact of genotypic matching, the prior literature supports its role in enhancing transfusion safety, particularly for high-risk populations like thalassemia patients.

This research explores the association between ABO blood groups and susceptibility to SARS-CoV-2 infection, analyzing Convalescent COVID-19 plasma (CCP) donors (n = 500) and healthy whole blood donors (BDs) (n = 9678) during the pandemic (1 May 2020 to 30 April 2021). A comparison is made with pre-pandemic BDs (n = 11,892) from 1 May 2018 to 30 April 2019. Significant differences in blood group distribution are observed, with blood group A individuals being three times more likely to be CCP donors. Conversely, blood groups B, O, and AB are less associated with CCP donation. Notably, blood group O is more prevalent among regular BDs, suggesting potential resistance to SARS-CoV-2 infection. This study underscores variations in blood group distribution during the pandemic compared to pre-pandemic periods. The findings support previous research indicating a link between blood group antigens and viral susceptibility, including SARS-CoV-2. Understanding these associations has implications for public health strategies, with potential for predicting COVID-19 outcomes and transmission patterns. Further research is crucial to explore molecular and immunological mechanisms, providing valuable insights for targeted preventive strategies and personalized healthcare in managing the impact of COVID-19.

Introduction. Daratumumab is a monoclonal antibody targeting CD38, commonly used in the treatment of newly diagnosed and relapsed multiple myeloma. The expression of CD38 on red blood cells poses a challenge as anti-CD38 can interact with red blood cells during the indirect antiglobulin test, complicating pre-transfusion testing and delaying the availability of antigen-negative blood units. Case Report. The first case involved a 49-year-old woman with anemia secondary to multiple myeloma, who had received treatment with Darzalex? three months prior. The second case was a 66-year-old woman with relapsed multiple myeloma, undergoing treatment with Darzalex?, who required a blood transfusion as part of her therapeutic protocol. Both patients? blood samples demonstrated complications during pre-transfusion testing, including panagglutination of red blood cells during the indirect antiglobulin test, affecting both antibody screening and cross-matching procedures. Following treatment of the red blood cells with Dithiothreitol, the indirect antiglobulin test results were rendered negative. However, since dithiothreitol destroys the Kell blood group antigen, both patients received Rh- and Kell-matched blood units to ensure compatibility. Conclusion. Dithioerythritol remains the most commonly available and effective method for resolving pre-transfusion testing issued in patients undergoing anti-CD38 monoclonal antibody therapy. Ensuring antigen matching patient for clinically significant blood group antigens between patient and donor red blood cells is crucial. Future efforts should focus on enhancing coordination between clinical teams and blood transfusion laboratories, developing unified guidelines, and investing in advanced testing modalities to overcome these transfusion challenges.

Introduction. Wra is an antigen of the Diego blood group system. Anti-Wra antibody can be found in the sera of healthy individuals (naturally occurring anti-Wra) or can be immunostimulated after transfusion or after exposure to foreign erythrocytes during pregnancy. Commercial anti-body identification panels do not routinely contain Wra antigen-positive erythrocytes. We present two cases of patient blood management in complex situations, such as antibody appearance to low-frequency Wra antigen. Case report. In the first presented patient, who received multiple blood transfusions, anti-Wra antibody was detected while solving cross-match incompatibility. In the second patient, anti-Wra antibody was identified during routine antierythrocyte antibody screening during pregnancy. Immunohematological testing included blood typing and antibody screening, cross-matching, antibody identification, indirect antiglobulin test (IAT), and direct antiglobulin test (DAT). Column agglutination technology with microtubes containing gel and standard tube test methodology were used in IAT and DAT. Conclusion. Due to the limitations of the screening test in detecting antibodies to clinically significant low-frequency blood group antigens, such as Wra, the recommendation when selecting erythrocytes or transfusion is to use units that are cross-match compatible by the IAT test at 37?C. In the case of anti-Wra antibody, as well as in cases of other antibodies to low-frequency antigens, immunohematology findings should be confirmed in a national or international reference laboratory that has the structure, organization, as well as technical and professional capacities to provide this service.