IntroductionLe cancer colorectal est la 2ème cause de mortalité par cancer en France (HAS, 2013) mais aussi le 3ème cancer le plus fréquent (INCa, 2014). Un dépistage organisé existe depuis 2008, pourtant, les taux de participation restent faibles : 33,5% en France (Santé Publique France, 20018). D’après la littérature, les principaux freins à la participation au dépistage sont le manque de confiance envers le système de soins (Clavarino et al, 2004) ; l’embarras, l’inconfort et le déplaisir accompagnant les procédures des tests (Varela et al, 2010) ; ou encore le manque de temps. Enfin, le manque de recommandations de la part du médecin représente l’un des freins les plus importants (Walsh et al, 2010 ; Powell et al, 2009). Le test Hémoccult II, utilisé dans le cadre du dépistage organisé jusqu’en mars 2015, a été remplacé par un nouveau test immunologique, jugé plus sensible, plus spécifique et plus fiable par la communauté médicale (INCa, 2014).Objectifs et méthodeAu regard des faibles taux de dépistage et des principaux freins identifiés dans la littérature, ce travail de thèse a pour but d’analyser les déterminants de la participation au dépistage à la fois du point de vue des patients mais aussi des médecins généralistes. De plus, il apparaît nécessaire d’évaluer les enjeux de l’arrivée du nouveau test immunologique.Ce travail doctoral est basé sur la technique de la triangulation (théorique, méthodologique et des données). Plus précisément, deux cadres théoriques validés et reconnus en psychologie sociale de la santé ont été mobilisés, à savoir la Théorie des Représentations Sociales (Moscovici, 1984), et la Théorie du Comportement Planifié (Ajzen et al, 1991), permettant l’adoption d’une approche compréhensive aussi bien que prédictive du dépistage. Trois études ont ainsi été développées :- Une étude qualitative par entretiens semi-directifs, menée auprès de 17 médecins généralistes, ayant pour but d’appréhender leurs représentations sociales du dépistage du cancer colorectal ainsi que la manière dont celui-ci peut s’ancrer dans leur pratique de recommandation ;- Une étude qualitative par focus groups, menée auprès de 29 participants issus de la population générale dont l’objectif était d’appréhender leurs représentations sociales du dépistage du cancer colorectal ainsi que les freins et facilitateurs à son adhésion.- Une étude quantitative par questionnaires, menée auprès de 160 participants issus de la population générale, visant à identifier les principaux prédicteurs de l’intention et du comportement de dépistage du cancer colorectal.Principaux résultatsL’analyse des entretiens a révélé une incohérence entre le rôle que les médecins pensent devoir jouer auprès des patients dans la prévention et le dépistage, et la réalité de leur pratique qui ne leur laisse que peu de temps à y consacrer. L’analyse des focus groups a révélé que les principaux freins à la participation au dépistage sont : le manque d’accessibilité du test (nécessité de consulter le médecin généraliste pour obtenir le kit de dépistage), une faible préoccupation pour la prévention, mais aussi le fait que le cancer colorectal se réfère à une partie du corps liée à un tabou, et considérée comme sale. Enfin, l’analyse des questionnaires a permis d’identifier plusieurs variables ayant une influence sur l’intention et le comportement de dépistage, à savoir : le comportement antérieur de dépistage, la fréquence de dépistage, le déni, la proximité sociale, les normes sociales et le contrôle comportemental perçu. Les analyses ont particulièrement mis en avant l’importance du contrôle comportemental perçu, pouvant agir directement sur le comportement sans passer par l’intention.ConclusionLes conclusions révèlent la pertinence d’allier une approche compréhensive à une approche prédictive. Nos perspectives proposent la mise en place d’interventions visant à améliorer le niveau de contrôle perçu de la population générale face à ce dépistage. / IntroductionColorectal cancer is the second leading cause of cancer deaths in France (HAS, 2013) but also the third most common cancer (INCa, 2014). An organized screening programme has been put in place since 2008, but participation rates remain low: 33.5% in France (Santé Publique France, 2018). According to the literature, the main barriers to participation in screening are the lack of confidence in the health care system (Clavarino et al, 2004) ; embarrassment, discomfort and dissatisfaction accompanying testing procedures (Varela et al, 2010); or lack of time. Finally, the lack of general practitioners’ recommendations is one of the most significant obstacles (Walsh et al, 2010, Powell et al, 2009). The Hemoccult II test, used as part of organized screening until March 2015, was replaced by a new immunological test, considered more sensitive, more specific and more reliable by the medical community (INCa, 2014).Objectives and methodFaced with the low screening rates and main obstacles identified in the literature, this thesis aims at analyzing the determinants of screening participation, with both patient and general practitioner points of view. Moreover, it appears necessary to evaluate issues with the arrival of the new immunological test.This doctoral work is based on the technique of triangulation (theoretical, methodological and data triangulation). More precisely, two validated and recognized theoretical frameworks in health and social psychology were employed, namely the Theory of Social Representations (Moscovici, 1984), and the Theory of Planned Behaviour (Ajzen et al, 1991), allowing the adoption of a comprehensive approach as well as a predictive approach to studying screening participation. Three studies have been set up:- A qualitative study through semi-structured interviews, conducted with 17 general practitioners, aimed at understanding their social representations of colorectal cancer screening and how it can be anchored in their practice of recommendation;- A qualitative study by focus groups, conducted with 29 participants from the general population. The objective was to apprehend their social representations of colorectal cancer screening as well as the obstacles and facilitators to screening participation.- A quantitative study by questionnaire, including 160 participants from the general population, endeavours to identify the key predictors of colorectal cancer screening intention and behaviour.Main resultsThe analysis of interviews revealed an inconsistency between the role general practitioners think they should play with patients in prevention and screening, and the reality of their practice which leaves them insufficient time to devote to it. The focus group analysis revealed that the main barriers to participation in screening are: the lack of accessibility of the test (needing to consult the general practitioner in order to obtain the screening kit), a low concern for prevention, but also the fact that colorectal cancer refers to a body part that is deemed taboo, and considered “dirty”. Finally, the analysis of questionnaires allowed the identification of several variables influencing intention and behaviour of screening, namely: previous screening behaviour, frequency of screening, denial, social proximity, social norms and perceived behavioural control. Analysis particularly emphasized the value of perceived behavioural control, which can directly influence behaviour without going through intention.ConclusionResults reveal the relevance of combining a comprehensive approach with a predictive approach. Our perspectives suggest the implementation of interventions aimed at improving the perceived level of control of the general population faced with this screening.

Made available in DSpace on 2016-12-23T13:55:59Z (GMT). No. of bitstreams: 1 Giuliana Schmidt Franca Fonseca.pdf: 1055751 bytes, checksum: 050d4de10b5fae8001c2b5f264473b60 (MD5) Previous issue date: 2013-08-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O diagnóstico de rotina da leishmaniose visceral (LV) humana é usualmente baseado em parâmetros clínicos e epidemiológicos, associado a exames parasitológicos e/ou imunológicos. Tendo em vista que a doença é fatal se não tratada, a busca por métodos diagnósticos mais efetivos, que sejam de fácil execução, simples, acessíveis, menos invasivos, e rápidos, se faz necessário, diminuindo o tempo de obtenção dos resultados. Portanto, neste estudo foi avaliado o desempenho de diferentes métodos já utilizados na rotina ou propostas como ferramentas alternativas para o diagnóstico da LV, incluindo o exame direto de punção de medula óssea, a reação de imunofluorescência indireta (RIFI), o teste rápido com rK39 (Kalazar Detect®), a ELISA com antígeno solúvel de L. chagasi e a imunofluorescência baseada em citometria de fluxo (FC-AFPA). Para isso foram avaliadas 77 amostras biológicas (punção de medula óssea e soro) de pacientes com diagnóstico clínico de LV, tratados e curados. A sensibilidade dos testes avaliados foi de 48% para o exame parasitológico direto, 74% para RIFI, 79% para o teste rápido com rK39, 88% para o teste ELISA-ASL e 94% para a FC-AFPA. A análise comparativa dos testes avaliados demonstrou que há maior concordância entre os testes sorológicos entre si, do que entre os testes sorológicos e o exame direto, devido a sua baixa sensibilidade. Foi também realizada a comparação entre os resultados dos testes sorológicos em relação ao resultado do teste parasitológico direto. Entretanto, nossos resultados mostraram que o desempenho dos testes foi semelhante independente do resultado do exame direto. Além disso, nosso estudo avaliou o desempenho de dois algoritmos para diagnóstico da LV baseados apenas em testes sorológicos. O primeiro deles utilizando a RIFI como teste de inicial, uma vez que este teste é disponibilizado pelo Ministério da Saúde (MS) para os laboratórios de referência em diagnóstico de LV e um segundo utilizando o teste rápido rK39, que tem sido recentemente sugerido como teste de triagem pelo MS. A análise dos dados demonstrou que o algoritmo para o diagnóstico da LV humana que apresentou melhor desempenho, ou seja, todos os casos foram detectados, foi aquele que utilizou o teste rápido como teste inicial, seguido de FC-AFPA / The routine diagnosis of human visceral leishmaniasis (VL) is usually based on clinical and epidemiologic parameters associated to parasitological and/or immunological tests. Being a fatal disease if not treated, the search for more effective, easy to perform, simple, affordable, and fast diagnostic methods, is necessary, decreasing the time to obtain results. Therefore, in this study the performance of different methods already used in the routine or proposed as alternative tools to the diagnose of VL was evaluated, which included the direct parasite detection (DPD) on bone marrow aspirates, indirect immunofluorescent assay (IFA), rK39 rapid test (Kalazar Detect®), ELISA test using L.chagasi soluble antigen, and immunofluorescence by flow cytometry (FC-AFPA). Seventy-seven biological specimens (bone marrow and serum) from patients with clinical diagnosis of VL, treated, and cured were assessed. The sensitivity of evaluated tests was 48% for DPD, 74% for IFA, 79% for rK39 rapid test, 88% for ELISA-SLA, and 94% for FC-AFPA. The comparative analysis demonstrated higher concordance among serological tests in comparison to serological tests and DPD, due to the low sensitivity of the latter. It was also done the comparison between the results of serological tests and direct examination. However, our results showed that the performance of tests was similar regardless of DPD results. In addition, our study evaluated the performance of two algorithms for the diagnosis of VL based only on serological tests. The first of them using IFA as a initial test, since this is the test provided by the Ministry of Health (MH) for reference laboratories for diagnosis of VL, and a second algorithm using the rK39 rapid test, that has recently been suggested as a screening test by the MH. It was demonstrated that the algorithm presenting the best performance, that is, all the cases were detected, was the one using rapid test as initial test followed by FC-AFPA