Irradiation of blood components with ionizing radiation generated by a specific device is recommended to prevent transfusion-associated graft-versus-host disease. However, a lin- ear accelerator can also be used in the absence of such a device, which is the case of the blood bank facility studied herein. In order to evaluate the quality of the irradiated packed red blood cells, this study aimed to determine whether the procedure currently employed in the facility is effective in inhibiting the proliferation of T lymphocytes without damaging blood components. The proliferation of T lymphocytes, plasma potassium levels, and the degree of hemolysis were evaluated and compared to blood bags that received no irradiation. Packed red blood cell bags were irradiated at a dose of 25 Gy in a linear accelerator. For this purpose, a container was designed to hold the bags and to ensure even distribution of irradiation as evaluated by computed tomography and dose-volume histogram. Irradiation was observed to inhibit the proliferation of lymphocytes. The percentage of hemolysis in irradiated bags was slightly higher than in non-irradiated bags (p-value >0.05), but it was always less than 0.4% of the red cell mass. Although potassium increased in both groups, it was more pronounced in irradiated red blood cells, especially after seven days of storage, with a linear increase over storage time. The findings showed that, at an appropriate dosage and under validated conditions, the irradiation of packed red blood cells in a linear accelerator is effective, inhibiting lymphocyte proliferation but without compromising the viability of the red cells.

El texto analiza el artículo 11 de la Declaración Universal sobre Bioética y Derechos Humanos de la Unesco que trata del principio de la no-discriminación y la no-estigmatización. Ambos conceptos están relacionados con el tema de la dignidad humana, al mismo tiempo en que la discriminación es parte inherente del estigma; no existe estigma si no hay discriminación. En este contexto, el trabajo pretende estudiar la relación entre estigma, discriminación y el HIV/Sida. El estudio defiende que para soltar las amarras que prenden los sujetos que están presos a ellas es necesario cuestionar las propias fuerzas más amplias - sociales, culturales, políticas y económicas - que estructuran el estigma, la estigmatización y la discriminación como procesos sociales directamente ligados a la producción y la reproducción de las desigualdades estructurales.

The text examines the article 11 of the Universal Declaration on Bioethics and Human Rights of UNESCO that deals with the principle of non-discrimination and non-stigmatization. Both concepts are related to the theme of human dignity, while discrimination is an inherent part of stigma: stigma does not exist if there is no discrimination. In this context, this paper aims to study the relationship between stigma, discrimination and HIV/AIDS. The study argues that to loosen the bonds that hold the subjects that are attached to them is necessary questioning the broader forces - social, cultural, political and economic - that structure stigma, stigmatization and discrimination as social processes directly linked to production and reproduction of structural inequalities.

O texto analisa o artigo 11 da Declaração Universal sobre Bioética e Direitos Humanos da UNESCO que trata do principio da não-discriminação e não-estigmatização. Ambos os conceitos estão relacionados com o tema da dignidade humana, ao mesmo tempo que a discriminação é parte inerente do estigma: não existe estigma se não houver discriminação. Neste contexto, o trabalho objetiva estudar a relação entre estigma, discriminação e o HIV/Aids. O estudo defende que para soltar as amarras que prendem os sujeitos que estão presos a elas é necessário questionar as próprias forças mais amplas - sociais, culturais, políticas e econômicas - que estruturam o estigma, a estigmatização e a discriminação como processos sociais diretamente ligados à produção e reprodução de desigualdades estruturais.

OBJETIVO: Vários aloanticorpos irregulares antieritrocitários, produzidos por sensibilizações a antígenos estranhos durante gestações ou transfusões, possuem importância clínica por provocarem hemólise no feto ou recém-nascido e/ou no receptor de sangue. Diante disso, fizemos uma análise prospectiva exclusiva de pacientes atendidos nos serviços de emergência clínica e cirúrgica, correlacionando as aloimunizações aos dados clínicos e epidemiológicos. MÉTODOS: Amostras sanguíneas de 143 pacientes, com pesquisa inicial de anticorpos negativa, foram coletadas até 15 meses após transfusões de concentrados de hemácias (CH), submetidas a Pesquisas de Anticorpos Irregulares (PAI) e, quando o resultado fosse positivo, à identificação e titulação seriada do(s) aloanticorpo(s). Para comparar proporções, foi empregado Teste Exato de Fisher e Odds Ratio. RESULTADOS: Dos pacientes estudados, 15 (10,49%) produziram aloanticorpos em um período de seis meses, com o título decaindo e negativando até 15 meses em 60% dos aloimunizados. Os aloanticorpos anti-K e os dirigidos contra antígenos do sistema Rh foram os mais frequente, o maior título foi de 1:32 (anti-K) e houve evidente correlação com o número de transfusões. CONCLUSÃO: Diante da alta ocorrência de aloanticorpos antieritrocitários de importância clínica em indivíduos transfundidos em serviço de emergência clínica e cirúrgica, propomos estender a fenotipagem e compatibilização pré-transfusional para os antígenos C, c, E, e (sistema Rh) e K (sistema Kell) para todos os pacientes com cirurgias programadas e/ou com eventos clínicos agudos que não necessitem de transfusões emergenciais.

BACKGROUND: Several irregular red blood cell alloantibodies, produced by alloimmunization of antigens in transfusions or pregnancies, have clinical importance because they cause hemolysis in the fetus and newborn and in transfused patients. OBJECTIVE: a prospective analysis of patients treated by the surgical and clinical emergency services of Hospital de Clínicas of the Universidade Federal do Triângulo Mineiro (HC/UFTM), Brazil was performed to correlate alloimmunization to clinical and epidemiological data. METHODS: Blood samples of 143 patients with initial negative antibody screening were collected at intervals for up to 15 months after the transfusion of packed red blood cells. Samples were submitted to irregular antibody testing and, when positive, to the identification and serial titration of alloantibodies. The Fisher Exact test and Odds Ratio were employed to compare proportions. RESULTS: Fifteen (10.49%) patients produced antibodies within six months of transfusion. However, for 60% of these individuals, the titers decreased and disappeared by 15 months after transfusion. Anti-K antibodies and alloantibodies against antigens of the Rh system were the most common; the highest titer was 1:32 (anti-K). There was an evident correlation with the number of transfusions. CONCLUSIONS: Given the high incidence of clinically important red blood cell alloantibodies in patients transfused in surgical and clinical emergency services, we suggest that phenotyping and pre-transfusion compatibilization for C, c, E, e (Rh system) and K (Kell system) antigens should be extended to all patients with programmed surgeries or acute clinical events that do not need emergency transfusions.

OBJECTIVE: Iron deficiency is the most common cause of anemia and one of the main factors in the clinical deferral of blood donors. This fact prompted the current study that aimed to determine the prevalence and etiology of anemia in blood donor candidates and to evaluate the hematological screening technique used for the exclusion of these donors. METHODS: This was a prospective study that compared two groups (Anemic and Non-anemic). Initially screening for anemia was performed by manually measuring hemoglobin (Bioclin® Kit); the results were subsequently compared with an automated screening method (Coulter T-890). The etiology was investigated by hemoglobin electrophoresis in alkaline and acid pH, Hb A2 dosage and measurement of the ferritin concentration by immunoagglutination. Differences and associations of interest were analyzed using the Yates and McNemar's Chi-square tests and the Fisher, Mann-Whitney, Wilcoxon and Kruskal-Wallis tests. RESULTS: The deferral rate due to anemia was 4.2%; iron deficiency was identified in 37.5% and beta thalassemia in 9.3% of the excluded candidates. There was a significant discrepancy between the two techniques used to measure hemoglobin with 38.1% of initially deferred donors presenting normal hemoglobin levels by the automated method. CONCLUSION: The results show a high rate of blood donors being deferred for anemia and confirm that iron deficiency is the most prevalent cause. The discrepancies found by comparing screening methods suggest that hemoglobin and hematocrit levels should be confirmed before deferring a donor due to anemia; this may increase supplies in blood banks.

OBJECTIVES: To identify the occurrence and the causes of platelet refractoriness in oncohematologic patients. INTRODUCTION: Platelet refractoriness (unsatisfactory post-transfusion platelet increment) is a severe problem that impairs the treatment of oncohematologic patients and is not routinely investigated in most Brazilian services. METHODS: Forty-four episodes of platelet concentrate transfusion were evaluated in 16 patients according to the following parameters: corrected count increment, clinical conditions and detection of anti-platelet antibodies by the platelet immunofluorescence test (PIFT) and panel reactive antibodies against human leukocyte antigen class I (PRA-HLA). RESULTS: Of the 16 patients evaluated (median age: 53 years), nine (56%) were women, seven of them with a history of pregnancy. An unsatisfactory increment was observed in 43% of the transfusion events, being more frequent in transfusions of random platelet concentrates (54%). Platelet refractoriness was confirmed in three patients (19%), who presented immunologic and non-immunologic causes. Alloantibodies were identified in eight patients (50%) by the PIFT and in three (19%) by the PRA-HLA. Among alloimmunized patients, nine (64%) had a history of transfusion, and three as a result of pregnancy (43%). Of the former, two were refractory (29%). No significant differences were observed, probably as a result of the small sample size. CONCLUSION: The high rate of unsatisfactory platelet increment, refractoriness and alloimmunization observed support the need to set up protocols for the investigation of this complication in all chronically transfused patients, a fundamental requirement for the guarantee of adequate management.

Despite major advances in Brazilian blood transfusion therapy with a growing number of scientific publications, an increased number of repeat donors and a decline in serological ineligibility, a lack of conformity in the application of pre-transfusion tests that may compromise transfusion safety is still observed at transfusion agencies in the fringes of the blood transfusion therapy system. Additionally, although high rates of platelet transfusion refractoriness and significant rates of alloimmunization have been demonstrated in the international literature, few Brazilian centers have been concerned with the study of platelet alloimmunization and even fewer centers have evaluated the efficacy of platelet concentrate transfusion. As more than one million Brazilians, including many repeat blood donors, are listed in the National Bone Marrow Donor Registry (Redome), why not grant transfusion therapy services access to the HLA typing of these blood and marrow donors after obtaining their consent? And why not make use of the Redome data to evaluate the HLA compatibility of donors for alloimmunized patients who are candidates for bone marrow transfusion and who have already been typed? These measures, together with the identification of ABO and HPA antigens, will permit a complete assessment of platelet immunology, will guarantee the transfusion safety of this blood component, and will put Brazil at the same level as the so-called developed countries in terms of transfusion medicine.

A terapêutica transfusional é uma das mais importantes intervenções da medicina. Sendo a transfusão de sangue um procedimento complexo, não isento de riscos e frequente no Centro de Terapia Intensiva - CTI, torna-se essencial uma atuação profissional competente. O objetivo deste estudo é descrever a formação dos profissionais médicos e de enfermagem que atuam em CTI, relacionada à prática transfusional. A pesquisa foi realizada em um hospital universitário localizado no Triângulo Mineiro. Foi aplicado um instrumento estruturado e confeccionado para conhecer a participação dos profissionais na prática transfusional e qual a sua abordagem no processo de formação. Referem participar do processo transfusional 64% dos profissionais de saúde, os quais se sentem informados sobre o assunto. No entanto, 54% não participaram de atualização, 73% não participaram de programas de capacitação e 89% receberam informação sobre alguns aspectos da transfusão através de aulas teóricas. Considerando os resultados, torna-se necessário rever o processo de formação destes profissionais, bem como dos programas de capacitação sobre medicina transfusional oferecidos pelas instituições.

Transfusion therapy is one of the most important interventions in medicine. However, blood transfusion is a complex proceeding, which is not devoid of risk but as it is common in the Intensive Care Unit (ICU), professional experience is essential. The objective of this study is to describe the level of instruction of medical and nursing professionals who work with transfusions in the Intensive Care Unit. This study was carried out in a University Hospital located in the Triângulo Mineiro region. A structured instrument was developed and applied to discover the professionals' participation in the transfusion practice and their approach to the process of instruction. About 64% of healthcare professionals participate in the transfusion process, all of whom felt they were informed about this subject. However, 54% did not participate in recycling training courses, 73% did not participate in training programs and 89% received information on some theoretical aspects of transfusion in classes. In light of the results, it is important to review the education of these professionals, as well as training programs on transfusion medicine offered by institutions.

O objetivo deste trabalho foi caracterizar a qualidade de vida de pacientes hemofílicos em acompanhamento ambulatorial em serviço especializado. Foi feita abordagem quantitativa da qualidade de vida (QV) de pacientes hemofílicos acompanhados em ambulatório de hematologia de um hemocentro regional. A coleta de dados foi realizada por meio de entrevistas utilizando-se o Whoqol-bref e questionário adicional com variáveis sociodemográficas e clínico-epidemiológicas. Para análise dos dados utilizaram-se o Epi-info 6.04d e o SPSS, cujos resultados foram expressos através de distribuição simples, medidas de tendência central e dispersão, proporções e correlação de Pearson entre facetas e domínios. Foram entrevistados 23 pacientes, com média de idade de 21 anos; todos moravam com familiares, 47,8% eram residentes na cidade sede do hemocentro. Do total, 78,3% eram solteiros, 69,6% estudavam, sendo que 45,5% possuíam o 1º grau incompleto e 82,6% não trabalhavam. A maioria (91,3%) possuía hemofilia A. Quanto à avaliação da QV, 47,8% responderam ser boa e 55% possuíam um bom nível de satisfação com a saúde. O domínio psicológico apresentou o maior escore médio e o menor foi o do domínio meio ambiente. Com esse estudo conseguiu-se salientar a magnitude de alguns problemas dos hemofílicos.

The objective of this work was to characterize the quality of life of hemophilic patients being followed up in a specialized service. A cross-sectional study of hemophilic patients in a Regional Blood Bank of Brazil was carried out to evaluate their quality of life. The data were obtained by interviews employing the WHO QOL-brief questionnaire, which was analyzed using SPSS and Epi-info 6.04d computer programs. Twenty-three male patients with a mean age of 21 years old were interviewed. All reported that they live with their families, 47.8% were residents in Uberaba, 78.3% were single, 69.6% were students with 45.5% having a low level of education and 82.6% did not work. Of the 23 cases, 91.3% had hemophilia A. In respect to quality of life, 47.8% responded that their quality of life was good and 55% had a good level of satisfaction with their health. The psychological dominion presented the highest average score and the environment presented the lowest. This study highlights the magnitude of some problems of hemophilic patients.

Como o controle de qualidade dos concentrados de plaquetas (CP), feito na data de seu vencimento, não possibilita distinguir o momento e o procedimento que determina a eventual redução de sua qualidade, decidimos investigar, separadamente, a influência da coleta, da produção e da estocagem sobre a qualidade deste hemocomponente. Foram avaliados, em 33 CP randômicos, diariamente, durante cinco dias, os seguintes parâmetros: a agregação, o número de plaquetas e leucócitos, a pO2 e pCO2, o pH, sódio e potássio, a presença de swirling, grumos, hemácias e lipemia e cultura para bactérias. Observamos maior queda da agregação plaquetária com pares de agonistas durante a produção dos CP (de 99,4% para 59,8%, p<0,01), seguida de queda gradativa durante a estocagem, atingindo 40,4% no quinto dia. Durante o período de estocagem observamos também: 1. queda gradativa da concentração de plaquetas (p<0,05), porém com valores sempre maiores que 5x10(10)/70 mL; 2. diminuição da concentração de leucócitos (p<0,05); 3. aumento da pO2 e queda da pCO2 (p<0,05); 4. aumento do pH (p<0,05 a partir do quarto dia) e da concentração de sódio e de potássio (em geral p<0,05); 5. swirling em todos os CP, grumos plaquetários em apenas um e ausência de hemácias e de lipemia em todos; e 6. negatividade das culturas para bactérias. Os resultados demonstram que as alterações foram mais evidentes no processo de produção e sugerem que o controle de qualidade dos CP deve contemplar da coleta ao final do período de estocagem.

As quality control of platelet concentrates obtained at the expiration date does not distinguish between the different stages that may cause reductions in quality, such as collection and storage, we decided to separately investigate the influence of collection, processing and storage on the quality of these blood components. This study evaluated 33 random platelet concentrates daily for five days for the following parameters: aggregation, number of platelets and leukocytes, PO2 and PCO2, pH, sodium and potassium, the presence of swirling, platelet clots, red blood cells and lipemia, and bacteria culture. We observed a greater decrease in platelet aggregation with pairs of agonists during the production of platelet concentrates (from 99.4% to 59.8%, p<0.05), followed by a gradual drop during storage reaching 40.4% on day five. During storage the following were also observed: 1. a gradual drop of platelet concentration (p<0.05) although the values always remained higher than 5x1010/70 mL; 2. a decrease in leukocyte concentration (p<0.05); 3. increases in pO2 and decreases in pCO2 (p<0.05); 4. increase in the pH (p<0.05 from day 4) and in concentrations of sodium and potassium (in general p<0.05); 5. swirling in all platelet concentrations, platelet clots in only one and absence of red blood cells and lipemia in all; and 6. negative cultures for bacteria. The results showed more apparent changes in the production process and suggest that the quality control of platelet concentrations should encompass all stages, from collection to the end of the storage period.

A leucemia/linfoma de células T do adulto é um distúrbio linfoproliferativo de linfócitos T maduros associado à infecção pelo vírus linfotrópico de células T humanas tipo I (HTLV-I). A leucemia/linfoma de células T do adulto tem polimorfismo clínico e laboratorial, que a classifica em quatro subgrupos distintos entre si: smoldering, crônica, aguda e linfomatosa. Apresentamos neste artigo, dois casos de leucemia/linfoma de células T do adulto, respectivamente, nas formas aguda e linfomatosa da doença. O caso 1: uma paciente de 35 anos apresentava distensão abdominal com hepato-esplenomegalia, adenomegalia, lesões cutâneas, anticorpos anti-HTLV-I positivo e leucocitose com presença de flower cell. O caso 2: homem de 38 anos, internado com linfadenomegalia generalizada, anticorpos anti-HTLV-I positivo, hipercalcemia e lesões osteolíticas. Neste artigo correlacionamos os achados clínicos e laboratoriais destes dois casos com dados da literatura.

Adult T-cell leukemia/lymphoma is a lymphoproliferative disorder of mature T lymphocytes associated with infection with human T-cell lymphotrophic virus type I (HTLV-I). Adult T-cell leukemia/lymphoma is characterized by clinical and laboratory polymorphism that allows it to be classified into four distinct subgroups: smoldering, chronic, acute and lymphomatous types. We present here two cases of adult T-cell leukemia/lymphoma, respectively in the acute and lymphomatous forms of the disease. Case 1 was a 35-year-old woman who presented abdominal distension accompanied by hepatosplenomegaly, adenomegaly, skin lesions, positivity for anti-HTLV-I antibodies and leukocytosis with the presence of flower cells. Case 2 was a 38-year-old man who was admitted with generalized lymphadenomegaly, positivity for anti-HTLV-I antibodies, hypercalcemia and osteolytic lesions. In this paper, we correlate the clinical-laboratory findings of these two cases with data in the literature.

O objetivo deste estudo foi avaliar a ativação plaquetária através da P-selectina e o conteúdo de PDGF-AB e TGFbeta1, nos pacientes com esquistossomose que desenvolveram fibrose (F3), naqueles que não tiveram esta manifestação (F0) e nos controles (C). Os resultados mostraram que a percentagem de P-selectina nas plaquetas sem estímulo de agonistas foi de 10,6% nos F3; 11,1% nos FO, e 6,3% nos C e após a adição de ADP/adrenalina, foi de 44%; 25,3% e 42%, respectivamente. A dosagem do PDGF-AB e TGFbeta1 por plaquetas foi de 11,016ng/dL (F3); 3,172 ng/dL (F0) e 5,01ng/dL (C) e, (0,012ng/dL (F3); 5,27ng/dL (F0) e 4,66ng/dL (C), respectivamente. Em relação à P-selectina, concluímos que as plaquetas dos pacientes com esquistossomoses, apesar de estarem pré ativadas, mantiveram-se responsivas aos agonistas. O TFGbeta1 não apresentou diferença entre os três grupos, enquanto o PDGF-AB foi significantemente maior no grupo F3, sugerindo a participação deste no desenvolvimento da fibrose.

The aim of this study was to evaluate platelet activation through P-selectin, and PDGF-AB and TGFbeta1 content, in schistosomiasis patients who developed fibrosis (F3) and who did not present this (F0), and in a control group (C). The results showed that the percentage of P-selectin in platelets without agonist stimulation was 10.6% in F3, 11.1% in F0 and 6.3% in C. After the addition of ADP/adrenaline, the percentages were 44%, 25.3% and 42%, respectively. The PDGF-AB and TGFbeta1 contents per platelet were 11,016ng/dl (F3), 3,172ng/dl (F0) and 5.01ng/dl (C) and 0,012ng/dl (F3), 5.27ng/dl (F0) and 4.66ng/dl (C), respectively. Concerning the P-selectin, we can conclude that platelets from patients with schistosomiasis continued to be responsive to agonists, despite being pre-activated. There were no differences in TGFbeta1 between the groups, but the PDGF-AB content was significantly higher in F3. This suggests that PDGF-AB may have some participation in the development of fibrosis.

Visando verificar a viabilidade do concentrado de plaquetas, após sua preservação com substâncias, que adicionadas ao sangue sejam capazes de destruir o Trypanosoma cruzi, testamos concentrado de plaquetas estocado com a violeta de genciana e a quinolina WR6026. A viabilidade foi avaliada através da contagem do número de plaquetas, da medida do pH e agregação plaquetária com par de agonistas durante seu período de estocagem. Alterações significativas foram observadas nos concentrados plaquetários tratados com violeta de genciana sugerindo comprometimento da viabilidade plaquetária. Com o WR6026 foram observados valores similares aos controles, abrindo perspectivas para o emprego deste sal na quimioprofilaxia da doença de Chagas transfusional, em regiões altamente endêmicas.

In order to verify the viability of platelet concentrate during its preservation period when added with two trypanosomicidal chemical substances, gentian violet and quinoline WR6026, we tested these concentrates and verified the following parameters: number of platelets, pH and platelet aggregation test with a pair of agonists. Significant alterations were observed in the platelet concentrate treated with gentian violet suggesting important damage to the platelet viability. With WR6026 similar values to the controls were observed, opening new perspectives for the utilization of this salt for the chemoprophylaxis of transfusional Chagas' disease in highly endemic regions.

Relata-se caso de metástases hematogênicas disseminadas e síndrome de Trousseau em mulher branca de 40 anos, portadora de câncer gástrico, apresentando hematoma subdural, equimoses, epistaxes, hemorragia gástrica e metrorragia. Inicialmente submetida à drenagem do hematoma, foi tratada sem sucesso com transfusões de plaquetas, hemácias e plasma crioprecipitado, além de antibióticos. O estudo de necropsia revelou adenocarcinoma gástrico com células em anel de sinete invadindo a serosa, com maciça coagulação intravascular disseminada e embolismo neoplásico sistêmico. Microtrombos hialinos (constituídos de fibrina e plaquetas) antigos e recentes, além de êmbolos tumorais, foram observados na medula óssea, meninges, fígado, pulmões, rins, linfonodos, adrenais, tireóide, coração, pâncreas e ovários (tumor de Krukenberg).

A case of widespread hematogenous metastases and Trousseau's syndrome is reported in a 40 year-old white housewife with gastric cancer, presenting subdural hematoma, ecchymoses, epistaxis, stomach and uterine bleeding. After undergoing hematoma drainage, she was unsuccessfully treated with platelets, red blood cells, plasma cryoprecipitate transfusions, and antibiotics. Necropsy disclosed gastric ring-signet adenocarcinoma invading the serous layer, with massive disseminated intravascular coagulation and systemic neoplastic embolism. Multiple old and recent hyaline (rich in fibrin and platelets) microthrombi, and tumor emboli were observed in the bone marrow, meninges, liver, lungs, kidneys, lymph nodes, adrenals, thyroid, heart, pancreas, and ovaries (Krukenberg tumor).

Estudou-se a distribuição do sistema ABO em 222 controles e em 148 chagásicos crônicos, assintomáticos e sintomáticos, com diferentes formas anatomoclinicas (insuficiência cardíaca congestiva, visceromegalias e morte súbita). O foi calculado a partir de tabelas de contingência e pelo método de Woolf. OX², obtido por estes dois métodos, demonstra que a freqüência do grupo OX² foi significativamente menor nos chagásicos sintomáticos considerados como um todo e naqueles com "megas", em relação aos controles. Nos chagásicos falecidos subitamente observou-se maior freqüência de grupos B que nos controles, sendo o X² significativo apenas quando calculado por tabelas de contingência. A relativa proteção aparentemente conferida aos chagásicos do grupo O, no que se refere à evolução para formas sintomáticas da doença, se explicaria por antigenicidade cruzada entre populações do Trypanosoma cruzi e o sistema ABO ou por outros fatores que se deixam influenciar ou influenciam a distribuição dos grupos sangüíneos.

ABO blood group distribution was studied in 222 Controls and in 148 symptomatic and symptomless patients with chronic Chagas' disease with different anatomo-clinics forms (congestive heart failure, visceromegalias and sudden death). The X² was estimated from contingency table and by Woolfs method. The X² obtained by these two methods showed that the group O frequency was significantly less in the symptomatic chagasic group as a whole and in those with "megas" when compared with the controls. B blood group was observed to be more frequent in chagasics with sudden death but the X² was only significant when calculated for contingency tables. The apparent relative protection confered by the O blood group to chagasics with respect to its evolution to symptomatic forms of the disease, could be explained by cross antigenicity among T. cruzi populations and ABO blood group or by other factors influencing or being influenced by the blood group distribution.