As micobactérias compreendem um grupo de organismos que são heterogêneos em termos de metabolismo, crescimento, nicho ambiental, epidemiologia, patogenicidade, distribuição geográfica e associação com doenças. O diagnóstico micobacteriológico é atualmente um desafio aos laboratórios. Com a descrição de novas espécies de micobactérias nos últimos anos, tem sido cada vez mais difícil identificar com precisão estas espécies. Uma questão básica na identificação em micobactérias é a diferenciação entre o Complexo Mycobacterium tuberculosis e as Micobactérias Não Causadoras de Tuberculose (MNT); no entanto tem sido cada vez mais importante a diferenciação das MNT. Em virtude das semelhanças fenotípicas e genotípicas, é necessário a aplicação e desenvolvimento de metodologias que melhor caracterizem as MNT para que seja possível determinar de forma mais precisa a prevalência das diferentes espécies. Além disso, diferentes espécies de MNT podem apresentar diferenças no perfil de sensibilidade às drogas terapêuticas, sendo que a identificação precisa é crucial para a adoção de terapia medicamentosa adequada. O objetivo deste trabalho foi caracterizar os isolados de MNT através da comparação entre duas técnicas moleculares, a técnica de PRA-hsp65 e um kit comercial GenoType® Mycobacterium CM, usando o método de sequenciamento do gene hsp65 como padrãoouro. Foram analisadas 96 isolados e a concordância entre os resultados do PRA-hsp65 e do GenoType® Mycobacterium CM foi de 92%. O método molecular PRA-hsp65 mostrou-se eficaz na identificação das espécies em 91% das amostras e o GenoType® Mycobacterium CM em 92%. Em relação aos custos referentes aos dois métodos, foi possível estabelecer que o PRA-hsp65 apresentou um valor final consideravelmente inferior ao do GenoType® Mycobacterium CM. No entanto, a técnica comercial necessita um prazo mais curto (2 dias) para ser realizada em comparação com a técnica PRA-hsp65 (requer 5 dias). Na nossa avaliação, a aplicabilidade do PRA-hsp65 aumenta a qualidade e rapidez do resultado final, já que se mostrou discriminatório, de baixo custo e relativamente de fácil execução na identificação de micobactérias. É possível concluir que ambas as técnicas moleculares avaliadas neste estudo apresentaram uma ótima capacidade de identificação de MNT, sendo que a implementação destas técnicas dependerá das características dos diferentes laboratórios bem como as necessidades clínicas das diferentes instituições. / Mycobacteria comprise a group of organisms that are heterogeneous in terms of metabolism, growth, environmental niche, epidemiology, pathogenicity, geographic distribution and disease association. The laboratory diagnosis of mycobacteria is currently a challenge to laboratories. Due to the increased description of new species of mycobacteria in recent years it is becoming difficult to accurately identify these species. A basic question in the identification of mycobacteria is the differentiation between Mycobacterium tuberculosis and the Non-Tuberculous Mycobacteria (NTM); however it has been increasingly important to differentiate the NTM species. Due to the fact that there are phenotypic and genotypic similarities, it is necessary to apply and develop methodologies to better characterize the NTM to be able to determine more accurately the prevalence of different species. Furthermore, different NTM species may differ in the profile of sensitivity to therapeutic drugs, and accurate identification is crucial for the adoption of appropriate drug therapy. The objective of this study was to characterize NTM isolates by comparing two molecular techniques, the technique of PRA-hsp65 (PCR-Restriction Enzyme Analysis) and a commercial kit GenoType® Mycobacterium CM, using the sequencing the hsp65 gene as gold standard. We analyzed 96 samples and the concordance between the results of the PRA-hsp65 and the GenoType® Mycobacterium CM was 92%. The PRA-hsp65 molecular method proved to be effective in 91% of species identification and the GenoType® Mycobacterium CM in 92%. Regarding costs for the two methods, we could establish that the PRA-hsp65 had a final value considerably lower than the GenoType® Mycobacterium CM. However, the commercial technique requires a shorter period (2 days) to be performed in comparison with the technique PRA-hsp65 (requires five days). In our evaluation, the applicability of the PRA-hsp65 increases the quality and speed of the final result (in relation to traditional phenotypic identification or outsourcing in referral centers), and proved to be discriminatory, inexpensive and relatively easy to perform the identification of mycobacteria. Finally, we conclude that both molecular techniques evaluated in this study showed a great capacity for identification of NTM and that the implementation of these techniques. However, depend on the characteristics of different laboratories as well as the clinical needs of different institutions.

The purpose of this study was to explore and describe the experiences of Grade 5 learners after being taught Natural Sciences by means of an enriched curriculum in the Win-LIFE (Wellness in Lifestyle, Intake, Fitness and Environment intervention) project. My focus thus fell on learners’ voices and perceptions, and more specifically with regard to the knowledge and skills that they gained in the Natural Sciences subject, as a result of a health-promotion intervention. For this purpose, I relied on Bronfenbrenner’s Bio-Ecological model (2005) as theoretical framework, and explored the learners’ experiences in a specific sub-system, being the Natural Sciences classroom and curriculum. I furthermore aimed to gain insight into how this can potentially be applied to other systems such as their home environments and personal lives. I used the interpretivist paradigm as meta-theory and followed a qualitative approach. I selected a case study design, applying Participatory Reflection and Action (PRA) principles, thereby aligning my study’s design to the broader research project for data generation and documentation I relied on multiple data generation sources, such as PRA-based workshops/discussions, observation, field notes, visual data documentation techniques and reflective journals to generate and document data. Following inductive thematic analysis three main themes and related subthemes emerged. Firstly, the experiential learning approach that was followed when implementing the intervention had positive outcomes in terms of learners’ attitudes toward learning, their commitment and self-confidence to make contributions in class, and their experiences of the learning process. Secondly, learners gained the necessary knowledge and skills of the Grade 5 Natural Sciences curriculum, and valued the practical experiences they acquired. In addition to their newly gained knowledge and skills being retained after a year, they finally also transferred the content to their parents, caregivers and family members, and reportedly applied what they had learned at home in their personal lives. Based on the findings of the study I can conclude that the learners experienced the enriched Natural Sciences curriculum in a positive manner and that their experiences resulted in positive outcomes and benefits for themselves and also those in their immediate environment. / Dissertation (MEd)--University of Pretoria, 2017. / Educational Psychology / MEd / Unrestricted

Rezension zum Reprint des ersten litauischen Buches Catechismvsa pra∫ty Szadei, erschienen zum 450-jährigen Jubiläums des Werkes

No description available.

Safety and risk assessment are key priorities for nuclear power plants. Probabilistic risk assessment (PRA) is a method for quantitative evaluation of accident risk, in particular severe nuclear core damage and the associated release of radioactive materials into the environment. The reliability and certainty of PRA have at times been questioned, especially when real-world observations have indicated that the frequency of nuclear accidents is higher than the probabilities predicted by PRA. This thesis provides a philosophical review of the epistemic uncertainties in PRA, using the Fukushima Daiichi accident of March 2011 as a case study. The thesis provides an overview of the PRA model structure, its key elements, and possible sources of uncertainty, in an attempt to understand the deviation between the real frequency of nuclear core-melt accidents and the probabilities predicted by PRA.The analyses in this thesis address several sources of epistemic uncertainty in PRA. Analyses of the PRA approach reveal the difficulty involved in covering all possible initiating events, all component and system failures, as well as their possible combinations in the risk evaluations. This difficulty represents the source of a characteristic epistemic uncertainty, referred to as completeness uncertainty. Analyses from the case study (the Fukushima Daiichi accident) illustrate this difficulty, as the PRA failed to identify a combined earthquake and tsunami, with the resultant flooding and consequent power failure and total blackout, as an initiating causal event in its logic structure.The analyses further demonstrate how insufficient experience and knowledge, as well as a lack of empirical data, lead to incorrect assumptions, which are used by the model as input parameters to estimate the probabilities of accidents. With limited availability of input data, decision-makers rely upon the subjective judgements and individual experiences of experts, which adds a further source of epistemic uncertainty to the PRA, usually referred to as input parameter uncertainty. As a typical example from the case study, the Fukushima Daiichi accident revealed that the PRA had underestimated the height of a possible tsunami. Consequently, the risk mitigation systems (e.g. the barrier seawalls) built to protect the power plant were inadequate due to incorrect input data.Poor assumptions may also result in improper modeling of failure modes and sequences in the PRA logic structure, which makes room for an additional source of epistemic uncertainty referred to as model uncertainty. For instance, the Fukushima Daiichi accident indicated insufficient backup of the power supply, because the possibility of simultaneous failure of several emergency diesel generators was assumed to be negligibly small. However, that was exactly what happened when 12 out of the 13 generators failed at the same time as a result of flooding.Furthermore, the analyses highlight the difficulty of modeling the human interventions and actions, in particular during the course of unexpected accidents, taking into account the physiological and psychological effects on the cognitive performance of humans, which result in uncertain operator interventions. This represents an additional source of epistemic uncertainty, usually referred to as uncertainty in modeling human interventions. As a result, there may be an increase in the probability of human error, characterized by a delay in making a diagnosis, formulating a response and taking action. Even this statement confirms the complexity of modelling human errors. In the case of the Fukushima Daiichi accident, lack ofvsufficient instructions for dealing with this "unexpected" accident made the coordination of operators' interventions almost impossible.Given the existence of all these sources of epistemic uncertainty, it would be reasonable to expect such a detected deviation between the real frequency of nuclear core-melt accidents and the probabilities predicted by PRA.It is, however, important to highlight that the occurrence of the Fukushima Daiichi accident could lie within the uncertainty distribution that the PRA model predicted prior to the accident. Hence, from the probabilistic point of view, the occurrence of a single unexpected accident should be interpreted with care, especially in political and commercial debates. Despite the limitations that have been highlighted in this thesis, the model still can provide valuable insights for systematic examination of safety systems, risk mitigation approaches, and strategic plans aimed at protecting the nuclear power plants against failures. Nevertheless, the PRA model does have development potentials, which deserves serious attention. The validity of calculated frequencies in PRA is restricted to the parameter under study. This validity can be improved by adding further relevant scenarios to the PRA, improving the screening approaches and collecting more input data through better collaboration between nuclear power plants world-wide. Lessons learned from the Fukushima Daiichi accident have initiated further studies aimed at covering additional scenarios. In subsequent IAEA safety report series, external hazards in multi-unit nuclear power plants have been considered. Such an action shows that PRA is a dynamic approach that needs continuous improvement toward better reliability.

No description available.

No description available.

A aloimunização contra antígenos plaquetários é um dos grandes desafios no tratamento de pacientes refratários à transfusão de plaquetas. OBJETIVOS: avaliar o desempenho de metodologias mais utilizadas em laboratórios de referência internacional para a pesquisa de anticorpos plaquetários (PAP); verificar a prevalência destes anticorpos na nossa população; avaliar se as transfusões estão causando aloimunização, e se estes aloanticorpos apresentam importância clínica. MATERIAIS E MÉTODOS: foram testadas amostras PRÉ e PÓS transfusionais em três grupos de pacientes sendo grupo 1 com patologias onco-hematológicas, grupo 2 com patologias não tumorais e grupo 3 composto dos mesmos tipos de pacientes do grupo 2 mas que não receberam transfusão (grupo controle). Numa primeira fase foi realizado estudo retrospectivo com amostras de soro congeladas no período de 1996 a 2001. A segunda fase consistiu em estudo prospectivo com amostras coletadas dos pacientes durante sua internação, no período de 2004 a 2006. Quatro diferentes metodologias foram testadas: imunofluorescência indireta por citometria de fluxo (PIFT), imobilização de antígenos plaquetários utilizando anticorpos monoclonais (MAIPA), teste de microlinfocitotoxicidade (LCT) e uma nova metodologia, conhecida como FLOW PRA&#8482;. Na fase 1 foram analisados 87 pacientes, e na fase 2, 96 pacientes, separados nos três grupos respectivamente. Na segunda fase do estudo, foi realizado o incremento da contagem corrigida de plaquetas (ICCp) para todos os pacientes que receberam transfusão de plaquetas. Para esta avaliação um novo grupo de pacientes (n=40) foi adicionado ao estudo, devido ao pequeno número encontrado na segunda fase. RESULTADOS: as metodologias testadas apresentaram diferenças nas freqüências dos anticorpos detectados, porém as metodologias MAIPA, PIFT e FLOW PRA&#8482; foram as mais concordantes entre si. A qualidade dos soros utilizados na fase 1 afetou os resultados encontrados devido ao seu prolongado tempo de armazenamento. Porém, este fato foi eliminado na fase 2, quando foram utilizados soros mais recentes. A prevalência de anticorpos encontrada foi de 22,6% nos pacientes do grupo 1 e 31,4% nos pacientes do grupo 2. Para o grupo 3 nenhum novo anticorpo foi detectado. A especificidade dos anticorpos encontrados foi na grande maioria HLA classe I (84%) seguido de anticorpos pan reativos com as glicoproteínas plaquetárias (8%) e anticorpos contra antígenos humanos plaquetários (HPA - 8%). A transfusão sangüínea apresentou associação significativa (p<0,05) com a presença de aloanticorpos somente nos pacientes do grupo 2. Os ICCp dos pacientes que apresentaram PAP reativa foram significantemente menores (p<0,05) que os ICCp dos pacientes que apresentaram PAP não reativas. Os pacientes com PAP reativas, ao receberam transfusões de plaquetas compatíveis passaram a apresentar ICCp semelhantes aos pacientes com PAP não reativa. Ao utilizar-se a refratariedade plaquetária como padrão-ouro para comparar as metodologias testadas verificou-se que não houve diferença entre as mesmas (p<0,05). CONCLUSÕES: A prevalência de anticorpos plaquetários é semelhante à encontrada na literatura. A transfusão estimulou a produção de anticorpos no grupo 2. Os anticorpos identificados apresentam importância clínica afetando o rendimento da transfusão de plaquetas. Devido a maior praticidade da técnica PIFT e dos bons resultados encontrados, sugerimos que esta deva ser utilizada como rotina para PAP em pacientes refratários. / The alloimmunization against platelet antigens is one of the great challenges in the treatment of platelet refractory patients. OBJECTIVES: To evaluate the performance of the most used methodologies for platelet antibodies screening (PAS); to verify the prevalence of these antibodies in our population; to evaluate if transfusions are causing alloimmunization, and if these alloantibodies present clinical importance. MATERIALS AND METHODS: samples were tested before and after transfusions in three groups of patients, Group 1 having onco-hematologic diseases, Group 2 having non-oncologic diseases, and Group 3 consisted of the same type of patients as Group 2 but had not received a transfusion (control group). In the first phase, a retrospective study was performed using frozen sera samples from 1996 to 2001. The second phase consisted of a prospective study with samples collected from patients during their internment, from 2004 to 2006. Four different methodologies were tested: the indirect Platelet Immunofluorescence Test (PIFT), the Monoclonal Antibody Immobilization of Platelet Antigen (MAIPA), the standard Lymphocytotoxicity Test (LCT) and a new methodology, known as FLOW PRA&#8482;. In Phase 1 87 patients were analyzed, and in Phase 2, 96 patients, separated into three groups respectively. In the second phase of the study, the Corrected Count Increment (CCI) was carried out for all patients who had received a platelet transfusion. For this evaluation a new group of patients (n=40) was added to the study, due to the low number found in the second phase. RESULTS: the methodologies presented differences in the frequencies of the detected antibodies; however MAIPA, PIFT and FLOW PRA&#8482; were the ones that were more concordant with each other. The quality of the sera used in Phase 1 affected the results due to long storage time. However, this event was eliminated in phase 2, when more recent sera were used. The prevalence of antibodies was 22.6% in the patients of Group 1 and 31.4% in the patients of Group 2. For Group 3 no new antibody was detected. The specificity of the antibodies was predominantly HLA class I antibodies (84%) followed by pan-reactive antibodies with platelet glycoproteins (8%) and antibodies against Human Platelet Antigen (HPA - 8%). Blood transfusion only presented a significant association (p<0.05) with the presence of alloantibodies in the patients of Group 2. The CCI of the patients who presented platelet antibodies was significantly less (p<0.05) that the CCI of the patients with non-antibodies. Patients with platelet antibodies, who received compatible platelet transfusions, showed similar CCI to the patients with non-reactive antibodies. There was no difference among the methodologies (p>0,05) to identify clinically significant antibodies. CONCLUSIONS: The prevalence of platelet antibodies is similar to that found in published literature. Transfusion stimulated the production of antibodies in group 2. The identified platelet antibodies present clinical importance affecting the efficiency of platelet transfusion. Due to the widespread use of the PIFT technique and the good results found, we suggest that this should be used as routine for PAP in refractory patients.

Der Inselstaat Fidschi im Südpazifik hat ein ausgeprägtes Landwirtschaftliches Wissenssystem mit einer Reihe privater und staatlicher Institutionen. Im Mittelpunkt der Untersuchung standen die staatlichen Agrarforschungs- und Beratungsabteilungen des Landwirtschaftsministeriums. Mit einem partizipativen Aktionsforschungsansatz wurde untersucht, welchen Beitrag partizipative Methoden zur Verbesserung des Informationsflusses zwischen Bauern und dem Ministerium leisten können, um damit eine systematische Integration der Probleme der Bauern im Wissenssystem zu erreichen. Weiterhin wurde erhoben, welchen Beitrag Plattformen für eine effizientere Arbeit im Ministerium leisten können. Partizipative Methoden (PRA) erwiesen sich als sehr geeignet den Dialog mit den Bauern zu fördern und deren Probleme zu analysieren. Neben den Problemen konnten auch die Potenziale der Betriebe und bäuerliche Lösungsvorschläge gut erfasst werden. Als Ergebnis wurde eine Modell zur systematischen Problemerfassung und Bestimmung von Forschungs- und Beratungsprioritäten erarbeitet. Der Trainingskurs in partizipativen Methoden zeigte folgende Stärken der lokalen Mitarbeiter auf: Organisieren von Untersuchungen, Anwendung partizipativer Methoden im Feld, praktische Implementierung, Visualisierung und Präsentation von Untersuchungsergebnissen. Schwachpunkte wurden hingegen in folgenden Bereichen festgestellt: konzeptionelles Denken, Interpretation und Auswertung der Daten sowie der schriftlichen Abfassung von Ergebnissen. Diese Defizite im konzeptionellen Bereich schränken das mit den Methoden erreichbare Problemlösungspotenzial ein. Weiterbildung der Mitarbeiter und eine Verbesserung der lokalen Agrarausbildung werden benötigt, um das Niveau der wissenschaftlichen Ausbildung anzuheben. Die Untersuchung von vier Projekten zeigte, dass diese als Plattformen gut zur Innovationsentwicklung und eingeschränkt zu deren Verbreitung geeignet waren. Eine ausgewogene Beteiligung aller Akteure zeichnete die erfolgreichste Plattform aus. Als Stärken des Plattformmodells konnten festgehalten werden: bessere Koordination, verbesserte Verbindungen und Schnittstellen, bessere Zusammenarbeit aller Akteure, bessere Aussichten gesetzte Ziele zu erreichen, Vermeidung von Doppelforschung und eine effiziente Ausnutzung der vorhandenen Ressourcen. Schwächen des Modells wurden in folgenden Punkten gesehen: Konsenserzielung, institutionelle Akzeptanz und Mangel an entsprechend ausgebildeten Fachkräften im Ministerium. Drei Jahre nach Beginn der Trainingsmaßnahmen konnte eine teilweise Institutionalisierung von partizipativen Methoden im Ministerium festgestellt werden. Zur weiteren Konsolidierung partizipativer Methoden und Plattformen wird eine Linkage-Abteilung empfohlen. / The small Island country Fiji has an articulated agricultural knowledge system with private and public institutions. The agricultural research and extension departments of the Ministry of Agriculture are the focus of this study. A participatory action research methodology was used to investigate the potential of participatory methods and to improve information flows between farmers and the Ministry in order to achieve a systematic Integration of farmers' problems into the knowledge system. Furthermore, the potential of platforms in improvement of the efficiency of work in the Ministry was studied. Participatory methods proved suitable in improving the dialog with farmers and the analysis of their problems. Besides this, farmers potentials and their ideas for solutions could be assessed. As a result, a model for the systematic compilation of farmers' problems and respective research and extension priorities could be elaborated. The training course on participatory methods revealed the following strength of Ministry staff: organising surveys, field use of tools, presentation and visualisation of findings. Conceptual thinking, analytical skills, interpretation, and report writing skills were identified as weaknesses. These deficits restrict the problem solving potential of participatory methods in the Ministry. Further education of Ministry staff and revised curricula at the local agricultural colleges will be required, to raise the overall level of scientific education. Four projects that were studied as cases for platforms, revealed that platforms were suitable means for promoting innovation development and somewhat less successful for the diffusion of findings. The most successful platform was characterised by a balanced contribution and participation of all actors involved. Strengths of the platform model were identified as such: better co-ordination, improved linkages, better interplay of actors, better means to reach goals, reduced duplication of efforts, and better use of resources. Weaknesses were seen in the need to achieve consensus and co-ordination, the weakening of hierarchical authority due to increased flexibility, and the fact that experienced-trained staff were not available in abundance in the Ministry. Three years after the first introduction of participatory methods in the Ministry, a partial institutionalisation could be observed. For the further consolidation of participatory methods and platforms, a linkage unit for further promotion is recommended.

A aloimunização contra antígenos plaquetários é um dos grandes desafios no tratamento de pacientes refratários à transfusão de plaquetas. OBJETIVOS: avaliar o desempenho de metodologias mais utilizadas em laboratórios de referência internacional para a pesquisa de anticorpos plaquetários (PAP); verificar a prevalência destes anticorpos na nossa população; avaliar se as transfusões estão causando aloimunização, e se estes aloanticorpos apresentam importância clínica. MATERIAIS E MÉTODOS: foram testadas amostras PRÉ e PÓS transfusionais em três grupos de pacientes sendo grupo 1 com patologias onco-hematológicas, grupo 2 com patologias não tumorais e grupo 3 composto dos mesmos tipos de pacientes do grupo 2 mas que não receberam transfusão (grupo controle). Numa primeira fase foi realizado estudo retrospectivo com amostras de soro congeladas no período de 1996 a 2001. A segunda fase consistiu em estudo prospectivo com amostras coletadas dos pacientes durante sua internação, no período de 2004 a 2006. Quatro diferentes metodologias foram testadas: imunofluorescência indireta por citometria de fluxo (PIFT), imobilização de antígenos plaquetários utilizando anticorpos monoclonais (MAIPA), teste de microlinfocitotoxicidade (LCT) e uma nova metodologia, conhecida como FLOW PRA&#8482;. Na fase 1 foram analisados 87 pacientes, e na fase 2, 96 pacientes, separados nos três grupos respectivamente. Na segunda fase do estudo, foi realizado o incremento da contagem corrigida de plaquetas (ICCp) para todos os pacientes que receberam transfusão de plaquetas. Para esta avaliação um novo grupo de pacientes (n=40) foi adicionado ao estudo, devido ao pequeno número encontrado na segunda fase. RESULTADOS: as metodologias testadas apresentaram diferenças nas freqüências dos anticorpos detectados, porém as metodologias MAIPA, PIFT e FLOW PRA&#8482; foram as mais concordantes entre si. A qualidade dos soros utilizados na fase 1 afetou os resultados encontrados devido ao seu prolongado tempo de armazenamento. Porém, este fato foi eliminado na fase 2, quando foram utilizados soros mais recentes. A prevalência de anticorpos encontrada foi de 22,6% nos pacientes do grupo 1 e 31,4% nos pacientes do grupo 2. Para o grupo 3 nenhum novo anticorpo foi detectado. A especificidade dos anticorpos encontrados foi na grande maioria HLA classe I (84%) seguido de anticorpos pan reativos com as glicoproteínas plaquetárias (8%) e anticorpos contra antígenos humanos plaquetários (HPA - 8%). A transfusão sangüínea apresentou associação significativa (p<0,05) com a presença de aloanticorpos somente nos pacientes do grupo 2. Os ICCp dos pacientes que apresentaram PAP reativa foram significantemente menores (p<0,05) que os ICCp dos pacientes que apresentaram PAP não reativas. Os pacientes com PAP reativas, ao receberam transfusões de plaquetas compatíveis passaram a apresentar ICCp semelhantes aos pacientes com PAP não reativa. Ao utilizar-se a refratariedade plaquetária como padrão-ouro para comparar as metodologias testadas verificou-se que não houve diferença entre as mesmas (p<0,05). CONCLUSÕES: A prevalência de anticorpos plaquetários é semelhante à encontrada na literatura. A transfusão estimulou a produção de anticorpos no grupo 2. Os anticorpos identificados apresentam importância clínica afetando o rendimento da transfusão de plaquetas. Devido a maior praticidade da técnica PIFT e dos bons resultados encontrados, sugerimos que esta deva ser utilizada como rotina para PAP em pacientes refratários. / The alloimmunization against platelet antigens is one of the great challenges in the treatment of platelet refractory patients. OBJECTIVES: To evaluate the performance of the most used methodologies for platelet antibodies screening (PAS); to verify the prevalence of these antibodies in our population; to evaluate if transfusions are causing alloimmunization, and if these alloantibodies present clinical importance. MATERIALS AND METHODS: samples were tested before and after transfusions in three groups of patients, Group 1 having onco-hematologic diseases, Group 2 having non-oncologic diseases, and Group 3 consisted of the same type of patients as Group 2 but had not received a transfusion (control group). In the first phase, a retrospective study was performed using frozen sera samples from 1996 to 2001. The second phase consisted of a prospective study with samples collected from patients during their internment, from 2004 to 2006. Four different methodologies were tested: the indirect Platelet Immunofluorescence Test (PIFT), the Monoclonal Antibody Immobilization of Platelet Antigen (MAIPA), the standard Lymphocytotoxicity Test (LCT) and a new methodology, known as FLOW PRA&#8482;. In Phase 1 87 patients were analyzed, and in Phase 2, 96 patients, separated into three groups respectively. In the second phase of the study, the Corrected Count Increment (CCI) was carried out for all patients who had received a platelet transfusion. For this evaluation a new group of patients (n=40) was added to the study, due to the low number found in the second phase. RESULTS: the methodologies presented differences in the frequencies of the detected antibodies; however MAIPA, PIFT and FLOW PRA&#8482; were the ones that were more concordant with each other. The quality of the sera used in Phase 1 affected the results due to long storage time. However, this event was eliminated in phase 2, when more recent sera were used. The prevalence of antibodies was 22.6% in the patients of Group 1 and 31.4% in the patients of Group 2. For Group 3 no new antibody was detected. The specificity of the antibodies was predominantly HLA class I antibodies (84%) followed by pan-reactive antibodies with platelet glycoproteins (8%) and antibodies against Human Platelet Antigen (HPA - 8%). Blood transfusion only presented a significant association (p<0.05) with the presence of alloantibodies in the patients of Group 2. The CCI of the patients who presented platelet antibodies was significantly less (p<0.05) that the CCI of the patients with non-antibodies. Patients with platelet antibodies, who received compatible platelet transfusions, showed similar CCI to the patients with non-reactive antibodies. There was no difference among the methodologies (p>0,05) to identify clinically significant antibodies. CONCLUSIONS: The prevalence of platelet antibodies is similar to that found in published literature. Transfusion stimulated the production of antibodies in group 2. The identified platelet antibodies present clinical importance affecting the efficiency of platelet transfusion. Due to the widespread use of the PIFT technique and the good results found, we suggest that this should be used as routine for PAP in refractory patients.