Gilberto A. Pereira

Socioepidemiological screening of serologically ineligible blood donors due to Chagas disease for the definition of inconclusive cases

Epidemiological screening combined with serological tests has become an important tool at blood banks for the characterization of donors with or without Trypanosoma cruzi infection. Thus, the objective of the present study was to describe the sociodemographic and epidemiological characteristics of blood donors with non-negative serology for T. cruzito determine possible risk factors associated with serological ineligibility. Sociodemographic and epidemiological data were collected by analysis of patient histories and interviews. The data were analyzed descriptively using absolute and relative frequencies and odds ratio (OR) evaluation. The frequency of serological ineligibility was 0.28%, with a predominance of inconclusive reactions (52%) and seropositivity among first-time donors (OR = 607), donors older than 30 years (OR = 3.7), females (OR = 1.9), donors from risk areas (OR = 4) and subjects living in rural areas (OR = 1.7). The risk of seropositivity was higher among donors who had contact with the triatomine vector (OR = 11.7) and those with a family history of Chagas disease (OR = 4.8). The results demonstrate the value of detailed clinical-epidemiological screening as an auxiliary tool for serological definition that, together with more specific and more sensitive laboratory methods, will guarantee a higher efficacy in the selection of donors at blood centres.

Epidemiological profile of hepatitis C in blood donors at the Uberaba Regional Blood Center

The aim of the present study was to outline the serological profile of hepatitis C among blood donors seen at the Uberaba Regional Blood Center, Hemominas Foundation, over the last 14 years. The frequency of hepatitis C was compared between first-time and repeat donors and the epidemiological characteristics of those with positive and indeterminate ELISA anti-HCV (third and fourth generation) were analyzed based on the donor histories kept in the archives of the Uberaba Regional Blood Center. The serological ineligibility rate was 0.3%, with higher prevalence in the group of first-time donors. We did not find any significant differences regarding age, skin color, marital status or place of residence between eligible and ineligible donors; however, the frequency of positive serology was higher among men. The lower (0.3%) rate of ineligibility due to hepatitis C that was observed at the Uberaba Regional Blood Center, in relation to most Brazilian blood centers, is probably due to the large number of repeat donors (83.3%). This reinforces the importance of achieving donor commitment for increasing transfusion safety.

Decline in the prevalence of HTLV-1/2 among blood donors at the Regional Blood Center of the City of Uberaba, State of Minas Gerais, from 1995 to 2008

INTRODUCTION A retrospective study was conducted in order to assess the prevalence and factors associated with seropositivity for HTLV-1/2 between 1995 and 2008 in Uberaba Regional Blood Center, and to describe the seropositive blood donors in relation to gender, age, marital status, skin color and origin. METHODS Descriptive statistical analysis, chi-square tests and odds ratios were produced to compare proportions, along with scatter charts with linear correlation coefficients. RESULTS Among the donors tested, the prevalence of seropositivity for HTLV was found to be 0.02%, with indeterminate results in 0.09%. There was a significant reduction in seropositivity for HTLV between 2002 and 2008, compared with the period from 1995 to 2001. Among the seropositive individuals, females were significantly predominant. CONCLUSIONS The gradual decrease in seropositivity over this period was attributed to the permanent exclusion of seropositive repeat donors and improvement in the clinical screening methods and serological tests over the years, with a positive impact on transfusion safety.INTRODUCAO: Estudo retrospectivo com o objetivo de avaliar a prevalencia e fatores associados a soropositividade para o HTLV-1/2, no periodo de 1995 a 2008, no Hemocentro Regional de Uberaba e descrever os doadores soropositivos quanto ao genero, idade, estado civil, cor de pele e procedencia. METODOS: Foram realizados analise estatistica descritiva, testes qui-quadrado e odds ratio para comparacao de proporcoes e grafico de dispersao com coeficiente de correlacao linear. RESULTADOS: Dentre x doadores testados, foi encontrada a prevalencia de sorologia positiva para o HTLV de 0,02% e indeterminada de 0,09%. Houve uma reducao significativa da sorologia positiva para HTLV, no periodo de 2002 a 2008, em comparacao ao periodo de 1995 a 2001. Dentre os soropositivos, observou predominio significante no genero feminino. CONCLUSOES: Imputamos a queda gradativa de soropositividade no periodo a exclusao permanente dos doadores de repeticao soropositivos e ao aprimoramento dos metodos de triagem clinica e dos testes sorologicos ao longo dos anos com reflexos positivos na seguranca transfusional.

Etiology of anemia of blood donor candidates deferred by hematologic screening

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 McNemars 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.

The Long-Term Bivariate Survival FGM Copula Model: An Application to a Brazilian HIV Data

In this paper we propose a new bivariate long-term distribu- tion based on the Farlie-Gumbel-Morgenstern copula model. The proposed model allows for the presence of censored data and covariates in the cure parameter. For inferential purpose a Bayesian approach via Markov Chain Monte Carlo (MCMC) is considered. Further, some discussions on the model selection criteria are given. In order to examine outlying and inuential ob- servations, we develop a Bayesian case deletion inuence diagnostics based on the Kullback-Leibler divergence. The newly developed procedures are illustrated on articial and real HIV data.

Perfil do doador de sangue autoexcluído no Hemocentro Regional de Uberaba-MG (HRU) no período de 1996 a 2006

Candidatos a doacao sao submetidos a triagem clinica e sorologica para minimizar o risco de transmissao de doencas via transfusao. Uma de suas limitacoes e a janela imunologica, que possibilita a transfusao de sangue contaminado. O objetivo deste trabalho foi avaliar o indice de autoexclusao de acordo com idade, genero, estado civil, cor e tipo de doacao, as variacoes anuais de autoexcluidos e sua eficacia em evitar a transfusao de sangue contaminado. Os dados foram analisados atraves do teste qui-quadrado, odds ratio e regressao linear. De 1996 a 2006, o Hemocentro Regional de Uberaba (HRU) coletou 176.097 bolsas de sangue, das quais 2,72% foram desprezadas por autoexclusao, com significativo predominio de homens, maiores de 29 anos, solteiros, nao brancos e primeira doacao (p<0,0001). Observou-se associacao entre fidelizacao e autoexclusao, sugerindo que maior fidelizacao contribui para menor autoexclusao. A sorologia positiva para HIV1 (0,35%) e HIV2 (0,23%) foi significativamente maior nos autoexcluidos (p<0,0001), significância nao observada para HCV (0,52%) (p=0,24). Nos nao autoexcluidos, estes percentuais foram de 0,15%, 0,03% e 0,41%, respectivamente. A maior frequencia de autoexclusao em homens maiores de 29 anos, solteiros e nao brancos esta de acordo, em parte, com o perfil do doador do HRU. O decrescimo de 1996 a 2001 e explicado por fatores comportamentais como criacao do Centro de Testagem Anonima e maior fidelizacao dos doadores ao longo dos anos. A maior frequencia de positividade nos autoexcluidos e tres soroconversoes em doacoes subsequentes reforcam a importância dessa ferramenta na diminuicao do risco de janela imunologica.

Freqüência de anticorpos irregulares em politransfundidos no Hemocentro Regional de Uberaba-MG, de 1997 a 2005

Testing of the pre-transfusional blood phenotype, which has been carried out at the Regional Blood Bank in Uberaba since 1996, is an important procedure to improve safety of blood transfusions. This study aims to describe the frequency of irregular red blood cell antibodies in multiple-transfused patients from 1997 to 2005. In a retrospective study, data from all alloimmunized patients were collected from the blood bank files. Descriptive statistical analysis was performed and a comparison of proportions was made using the Z test. Alloimmunization was observed in 173 (0.75%) of the 23,220 transfused patients, with an average of 5.7 transfusions per patient. The frequency of the Rh and Kell systems jointly was over 70%. The proportion of anti-D was significantly higher in women (p<0.05) and no difference was noted in the Rh system between Caucasians and non-Caucasians. Seventy percent (70%) of the patients were over 30 years of age. Out of the 73 patients with registered diseases, 39.73% had acute anemias, 31.51% chronic anemias and 28.77% oncological or onco-hematologic diseases. Approximately 70% of antibodies were discovered before the 10th transfusion. The low frequency of alloimmunization observed at the Regional Blood Bank of Uberaba reinforces the importance of pre-transfusional blood phenotype screening for all multiple-transfused patients as well as its adoption as a common practice in all hemotherapy center.

Importância dos testes sorológicos de triagem e confirmatórios na detecção de doadores de sangue infectados pelo vírus da hepatite C

A triagem sorologica de doadores de sangue com baixos indices de prevalencia de infeccao, como no caso da hepatite C (HCV), gera um percentual consideravel de resultados falso-positivos e descarte de bolsas de hemocomponentes frequentemente nao infectados. O objetivo deste estudo foi pesquisar o perfil sorologico e, com base no teste confirmatorio, a ocorrencia de hepatite C nos doadores com sorologia positiva ou indeterminada do Hemocentro Regional de Uberaba (HRU). Os testes confirmatorios foram realizados por meio da deteccao do RNA do HCV no plasma, utilizando-se o metodo RT-PCR qualitativa. Foram realizadas, no periodo de 1992 a 2005, 171.027 doacoes de sangue no HRU, sendo 24,3% de doadores iniciais e 75,7% de retorno. O indice de inaptidao para HCV foi de 0,3% (561 doacoes), sendo que 53,0% destas eram de doadores iniciais e 47,0% de retorno, com prevalencias de 0,5% e 0,2%, respectivamente (p<0,0001). O indice de reacoes inconclusivas foi significativamente maior nos doadores de retorno (p=0,0214). Noventa e oito candidatos foram submetidos a PCR qualitativa e apenas 34 (34,7%) apresentaram resultados positivos, com indice de positividade significativamente menor nos doadores de retorno (p=0,0184) e quase tres vezes menor nos inconclusivos. Assim, verificamos que grande numero de doadores, tanto anti-HCV positivos quanto indeterminados, nao tiveram confirmada a presenca da infeccao pelo HCV, levando-nos a concluir que a inaptidao sorologica para hepatite C no HRU, na maioria das vezes, nao correspondeu a presenca de infeccao viral no doador.

The importance of hemovigilance in the transmission of infectious diseases

Background Hemovigilance is an organized system of surveillance throughout the transfusion chain intended to evaluate information in order to prevent the appearance or recurrence of adverse reactions related to the use of blood products. Objective The aims of this study were to assess the late reporting of incidents related to possible seroconversion in respect to age, marital status and ethnical background, annual variations in late reporting, the number of reports opened and closed, seroconversion of donors and transfusions of blood products within the window period. Methods This retrospective, descriptive study used data on blood donations in the blood bank in Uberaba during the period from 2004 to 2011. Some socio-epidemiological characteristics of the donors and serology test results of donors and recipients were analyzed in respect to the late reporting of incidents related to possible seroconversion. The Chi-square test, odds ratio and a regression model were used for statistical analysis. Results From 2004 to 2011, the blood bank in Uberaba collected 117,857 blood bags, 284 (0.24%) of which were investigated for late reported incidents. The profile of the donors was less than 29 years old, unmarried and non-Whites. Differences in age (p-value < 0.0001), marital status (p-value = 0.0002) and ethnical background (p-value < 0.0001) were found to be statistically significant. There was no statistical difference between men and women (0.24% and 0.23% respectively; p-value = 0.951). The number of late reported incidents increased until 2008 followed by a downward trend until 2011. There were twelve cases of seroconversion in subsequent donations (seven human immunodeficiency virus, four hepatitis B and one hepatitis C) with proven human immunodeficiency virus infection after screening of only one recipient. Conclusion The twelve cases of seroconversion in donors with subsequent infection proven in one recipient underscores the importance of this tool to increase transfusion safety.

A General Latent Class Model for Performance Evaluation of Diagnostic Tests in the Absence of a Gold Standard: An Application to Chagas Disease

We propose a new general Bayesian latent class model for evaluation of the performance of multiple diagnostic tests in situations in which no gold standard test exists based on a computationally intensive approach. The modeling represents an interesting and suitable alternative to models with complex structures that involve the general case of several conditionally independent diagnostic tests, covariates, and strata with different disease prevalences. The technique of stratifying the population according to different disease prevalence rates does not add further marked complexity to the modeling, but it makes the model more flexible and interpretable. To illustrate the general model proposed, we evaluate the performance of six diagnostic screening tests for Chagas disease considering some epidemiological variables. Serology at the time of donation (negative, positive, inconclusive) was considered as a factor of stratification in the model. The general model with stratification of the population performed better in comparison with its concurrents without stratification. The group formed by the testing laboratory Biomanguinhos FIOCRUZ-kit (c-ELISA and rec-ELISA) is the best option in the confirmation process by presenting false-negative rate of 0.0002% from the serial scheme. We are 100% sure that the donor is healthy when these two tests have negative results and he is chagasic when they have positive results.