Original Article Titers of ABO antibodies in group O blood donors Natalia Dallaval Galvão de França Mônica Caamaño Cristovão Poli Patrícia Guilhem de Almeida Ramos Cláudia Strang da Rocha Borsoi Rafael Colella Banco de Sangue de São Paulo, São Paulo, SP, Brazil Conflict-of-interest disclosure: The authors declare no competing financial interest Submitted: 6/2/2010 Accepted: 4/13/2011 Corresponding author: Natalia Dallaval Galvão de França Rua Itapura, 181 apto 04 – Vila Alpina 09090-320 – Santo André, SP, Brazil dallaval1@hotmail.com www.rbhh.org or www.scielo.br/rbhh DOI: 10.5581/1516-8484.20110073 Background: Plasma components of group O blood donations are rarely submitted to ABO antibody titrations even though it is well known that passively acquired antibodies may destroy the recipient`s own red cells and tissue grafts. Objective: Thus, group O donations stratified by gender and age were randomly titrated to identify the best source of products for apheresis and exsanguinous transfusion. Methods: Samples from 603 blood donors were tested by ABO antibody titration using the conventional tube technique at room temperature. ABO antibody levels higher than 64 were considered high. After correction for gender, statistical analyses were performed using the Fisher exact and Kruskal-Wallis tests. Results: Most donors in the blood bank were male (65.7%). ABO antibody titers ranged from 1 to 2048. The estimations of prevalence for the titers were: anti-A,B < 128 = 86.9% and > 128 = 2.16%; Anti-A > 128 = 9.29% and anti-B > 128 = 4.81%. Low mean titers for both anti-A and anti-B antibodies were found in over 50-year-old men (p-value = 0.040). High anti-B antibody levels were found in young women (p-value = 0.002). Conclusion: This study confirms that over 50-year-old O group men should be selected as blood donors in non-identical ABO transfusion situations. Also, titration of ABO antibodies in blood banks will increase safety in non-identical ABO transfusions. Keywords: ABO Blood-Group System; Blood donors; Blood transfusion; Blood group antigens; Blood platelets/immunology; Agglutination tests/methods; Agglutinins; Antigen-antibody reactions Introduction One century after the discovery of the ABO blood group system, most currently used techniques in blood banks are still based on the principle of interactions between antigen and antibody and subsequent agglutination of red blood cells. Tests that identify the antibody indicate the probable specificity of the antibody, but whether an antibody will destroy red blood cells bearing the corresponding antigen depends of various conditions. The concept of compatibility encompasses much more than crossmatching.(1) The use of O blood group transfusions to patients of all groups has continued since the Second World War; nevertheless the transfusion of group O plasma to group A recipients sometimes causes severe red cell destruction. Acute hemolysis has been reported following transfusion of non-iso group single donor platelet (PLT) concentrates and may be more common than is appreciated. Other effects of incompatible plasma include hemoglobinemia, jaundice, progressive anemia, spontaneous agglutination, positive direct antiglobulin test and increased osmotic fragility of the patient's red cells.(2) Levels of A and B antibodies appear to be influenced mainly by environmental factors and anti-A and anti-B molecules may be IgM, IgG or IgA. Some sera contain all three classes and non-stimulated individuals are predominantly IgM. Changes in the characteristics of anti-A or anti-B occur as a result of further immunization with pregnancy or by incompatible transfusions. They are serologically detectable through increases in titers, agglutinin avidity and hemolytic activity and have greater activity at 37ºC. Such "immune" sera are generally difficult to inhibit with saliva or with A or B substances. Sera from group O people contain two separable antibodies, anti-A and anti-B and a cross- reacting antibody called anti-A,B (mostly IgG).(3) It is a challenge to understand how the role of ABO antibodies influences the fate of organ grafts after transplantation. Japanese groups have pre-transplant preparative regimens that include titration, immunosuppression and splenectomy associated to a therapeutic plasma exchange (TPE) program. However, there is only limited basic research within this area and a lack of standardized clinical protocols for TPE.(4) On the other hand, in transfusion medicine, from 10 to 40 percent of all PLTs transfusions in the United Rev Bras Hematol Hemoter. 2011;33(4):259-62 259