Current literature lacks longitudinal understandings of the association between childhood sexual/physical violence, alcohol use, depressive symptoms, and indiscriminant sexual behaviors among young women, as well as the racial/ethnic differences in these associations. Therefore, using the 1994-2008 National Longitudinal Study of Adolescent Health, this study examined a) heterogeneous growth trajectories of problem alcohol use during the transition from adolescents to young adulthood and the impact of childhood sexual/physical violence on drinking trajectories, b) the long-term impact of childhood sexual/physical violence on alcohol use and depressive symptoms, and c) the structural associations between childhood sexual/physical violence and indiscriminant sexual behaviors by examining alcohol use and depressive symptoms as mediators between White and African-American women. First, with 1,702 women, LCGM was used to identify trajectories of problem alcohol use using the first three waves. Four trajectories of problem alcohol use emerged: stable abstainers; decliners (moderate-low); incliners (low-moderate); and rapid incliners (low-high). From the bivariate level analyses, in reference to stable abstainers, White women who experienced childhood sexual/physical violence were more likely to be rapid incliners (low-high). Second, with 1,756 women, autoregressive cross-lagged path models were performed to test longitudinal associations between childhood sexual/physical violence, problem alcohol use, and depressive symptoms of White and African-American women. Both groups demonstrated significant association between childhood sexual/physical violence and subsequent development of depressive symptoms, while only White women demonstrated significant association with subsequent problem alcohol use. Third, with 1,388 women, SEM and multigroup SEM were used to test pathways between childhood sexual/physical violence and indiscriminant sexual behaviors for White and African-American women. SEM indicates that problem alcohol use and depressive symptoms mediated the proposed relationship. Multigroup SEM indicates that, for White women, both problem alcohol use and depressive symptoms mediated the association between childhood sexual/physical violence and indiscriminant sexual behaviors, while only depressive symptoms mediated the proposed association for African-American women. These findings highlight the importance of designing and providing effective prevention and treatment programs for women who experienced childhood sexual/physical violence to interrupt subsequent problem alcohol use, depressive symptoms, and indiscriminant sexual behaviors. / text

This study was part of a larger multi-informant longitudinal study with a sample of 319 children (52% male, 48% female) ages 4-12 (mean= 7 years 9 months) whose parents had recently filed for divorce. Three annual waves of data from four informants were used for analysis: child self-report, mother, teacher, and observer report. The purpose of the study was to add to the understanding of multi-informant research and children’s psycho-social well-being. The first goal was to determine the consensus of children’s psycho-social well-being scores within informant across time, within child across informant, and between children over time. The second goal was to determine factors that contribute to the levels of consensus, such as, child gender, child age, child ethnicity, and length of parents’ separation, maternal baseline depressive symptoms score, and timing of the teacher questionnaire. The third goal was to determine if children could be classified into meaningful psycho-social well-being groups. Lastly, a visual diagnostic tool, the “patchwork”, was created using a random sample of eight prototypical cases of group membership based on predicted probabilities. This tool displayed the four informants scores, and child and informant characteristics. A single measure of child psycho-social well-being was created for each informant to compare rater consensus in hierarchical linear modeling. Latent class analysis was used to determine groupings. The HLM results indicate that 53% of the variance is within informants across time, 31% is within child across raters, and only 16% is between child over time. As expected, results showed more consensus of informants’ scores among girls than boys, the greatest consensus for children in middle childhood over other age groups, among Non-Hispanic White children compared to other ethnicities, and among spring reports than fall reports from teachers. Maternal baseline depressive symptoms score was significantly related to level of consensus of reporters, with greatest consensus when mother’s baseline depressive symptoms scores are at the mean (15.47). Mother’s scores of children’s psycho-social well-being decrease from highest scores of when baseline depressive symptoms score is 0, decreasing -.02 with each point increase in baseline depressive symptoms score. The results of the latent class analysis show two latent classes with maternal baseline depressive symptoms as a covariate best fit the data, one class with psycho-social well-being scores above the mean (N=258), and one with scores below the mean (N=61). Baseline data alone sufficiently models these groups and is chosen for parsimony over latent transition analysis. In sum, this study demonstrated benefits of multi-method multi-informant research, while acknowledging the strengths and biases that influence informant consensus of children’s psycho-social well being / text

No description available.

Using the E. coli vaccine as a case study, this thesis examines the factors affecting the adoption of technologies with positive spillover (externality) effects related to food safety. Positive spillovers occur when the benefits from a technological innovation extend beyond the firm (farm) adopting the technology or they do not flow to the adopter. If there are insufficient incentives for the firm to adopt the new technology, adoption levels are sub-optimal, resulting in forgone benefits to society. These benefits include the avoidance of potential health costs, productivity loss and premature death costs as a result to exposure to E. coli O157:H7. Therefore, if the market incentives to adopt the technology are strengthened, adoption levels of the technology could reach socially optimal levels resulting in an improvement in food safety. This has been the case in the Canadian cattle industry, where the uptake of the E. coli vaccine by cow-calf producers has been very low. As such, a number of potential incentives to increase adoption of the vaccine were identified and assessed through a survey of cow-calf producers on the Prairies. Data from the survey were analyzed using a stated preference methodology, Best-Worst Scaling, and Latent Class cluster analysis. A Binary Probit Model was also used to examine the factors affecting willingness to adopt the vaccine. The results suggest that a significant number of producers were not aware of the existence of the E. coli vaccine. In addition, producers were most likely to be influenced in their adoption decisions by market/supply chain oriented incentives and government intervention incentives in the form of subsidies. On the other hand, incentives that were least likely to influence cow-calf producers’ decisions to adopt included government intervention through recommending use of vaccine and neighbours (other cow-calf producers) adopting the vaccine. The Latent Class cluster analysis revealed the existence of three unique producer clusters with different attitudes towards these incentives. Several socio-demographic variables and individual characteristics utilized in the Probit analysis were found to be determinants of a producer’s willingness to adopt an E. coli vaccine. The implications of this research are such that producer education and awareness campaigns may be utilized as tools for disseminating information on food safety technologies such as the E. coli vaccine. Furthermore, the market/supply chain incentives may be used to form potential market-based solutions to address the current low adoption rates. The existence of three unique producer clusters suggest that a one-size fits all strategy to encourage the adoption of the E. coli vaccine might be difficult to implement and thus a more targeted approach may be a feasible alternative.

New Zealand is internationally renowned for having some of the finest and most challenging trout fishing in the world. However, due to continuing development and angling pressure many fishing sites are showing signs of environmental degradation and over fishing. This trend is almost certain to continue into the future given continued population and economic growth. Understanding the determinants of site choice, preference heterogeneity and anglers’ substitution patterns is fundamentally important to fishery managers who have the difficult task of maintaining quality angling experiences on a number of fishing sites, managing angling pressure and maintaining license sales. Recent advances in simulation techniques and computational power have improved the capability of discrete choice models to reveal preference heterogeneity and complex substitution patterns among individuals. This thesis applies and evaluates a number of state-of-the-art discrete choice models to study angler site choice in New Zealand. Recreation specialisation theory is integrated into the analysis to enhance the behavioural representation of the statistical models. A suite of models is presented throughout the empirical portion of this thesis. These models demonstrate different ways and degrees of explaining preference heterogeneity as well as identifying anglers’ substitution patterns. The results show that North Canterbury anglers’ preferences vary considerably. Resource disturbances such as riparian margin erosion, reduced water visibility and declines in catch rates can cause significant declines in angler use of affected sites, and at the same time non-proportional increases in the use of unaffected sites. Recreation specialisation is found to be closely related to the types of fishing site conditions, experiences and regulations preferred by anglers. Anglers’ preference intensities for fishing site attributes, such as catch rates, vary across different types of fishing sites. This location specific preference heterogeneity is found to be related to specialisation. Overall, the empirical findings indicate that conventional approaches to modelling angler site choice which do not incorporate a strong understanding of angler preference heterogeneity can lead to poorly representative models and suboptimal management and policy outcomes.

Submitted by Maria Creuza Silva (mariakreuza@yahoo.com.br) on 2015-07-14T19:35:02Z No. of bitstreams: 1 TESE GISEL FATORE. 2015.pdf: 3095009 bytes, checksum: becebe9f8956330c8c568ff335a8e172 (MD5) / Approved for entry into archive by Maria Creuza Silva (mariakreuza@yahoo.com.br) on 2015-07-14T20:45:28Z (GMT) No. of bitstreams: 1 TESE GISEL FATORE. 2015.pdf: 3095009 bytes, checksum: becebe9f8956330c8c568ff335a8e172 (MD5) / Made available in DSpace on 2015-07-14T20:45:28Z (GMT). No. of bitstreams: 1 TESE GISEL FATORE. 2015.pdf: 3095009 bytes, checksum: becebe9f8956330c8c568ff335a8e172 (MD5) / A asma é uma doença urbana complexa com múltiplos fatores associados ao seu desenvolvimento e remissão. Muitos fatores de risco para a doença foram identificados, e existe um debate sobre a contribuição dos fatores psicossociais na gênese da asma. A discriminação racial configura-se como um importante estressor psicossocial com efeitos negativos sobre a saúde. No entanto, os efeitos da discriminação sobre a asma infantil não tem sido investigados. Este estudo teve como objetivo analisar o efeito da exposição à discriminação em mulheres sobre a prevalência de asma nas crianças. Trata-se de um estudo transversal sobre a população integrante do programa Social Changes Asthma and Allergy in Latin America (SCAALA) em Salvador. A tese foi desenvolvida sob a forma de quatro artigos, tendo o primeiro como objetivo avaliar a confiabilidade e estrutura dimensional do “Experiência de Discriminação” (Experience of Discrimination - EOD), um instrumento de mensuração das experiências de discriminação desenvolvido nos Estados Unidos. Identificaram-se dois indicadores de discriminação: a experiência de discriminação e a preocupação com discriminação, com parâmetros aceitáveis de ajuste para o EOD no contexto brasileiro. O segundo artigo mensurou a prevalência de discriminação auto relatada utilizando analise de classes latentes. Os indivíduos foram classificados perfis de discriminação alto e baixo. A frequência das classes expostas à discriminação ou preocupadas com discriminação mostraram-se altas, principalmente no que respeita ao emprego e trabalho, com a cor da pele como um importante preditor das experiências relatadas. Já o terceiro artigo analisou o efeito da discriminação sobre a prevalência de transtornos mentais comuns nas mulheres participantes do estudo, evidenciando maiores prevalências de TMC entre aquelas mulheres que referiram alto grau de exposição à discriminação ou preocupação com discriminação. O suporte social moderou a associação entre preocupação com discriminação e sofrimento mental. Finalmente, o quarto artigo estimou o efeito da discriminação referida pelas mães sobre a prevalência de asma nos filhos. Os resultados corroboraram a hipótese de que a exposição à discriminação racial nas mães se associa com sintomas asmáticos nas crianças, e com o fenótipo atópico. Em acordo com nossa hipótese de estudo, mães com sintomas psicológicos foram mais propensas a ter filhos com sintomas asmáticos quando expostas a discriminação que àquelas sem sintomas. Os achados deste estudo destacam a importância de estudar a discriminação racial no contexto brasileiro. Embora esses resultados necessitem ser confirmados em estudos longitudinais, contribuirão com a compreensão de uma doença complexa como a asma em crianças.

Les études diagnostiques correspondent à l’ensemble des études cliniques qui ont pour objectif l’évaluation d’un nouveau test diagnostique. Dans la démarche d’évaluation, l’étape centrale est l’évaluation de la performance du nouveau test par estimation de sa sensibilité et de sa spécificité. De manière classique, la performance du nouveau test est évaluée par comparaison à un test de référence supposé parfait, appelé un « gold standard » qui permet la connaissance du statut réel de chaque sujet vis-à-vis de la pathologie étudiée. Cependant, dans de très nombreuses situations cliniques, différentes difficultés existent : l’absence de gold standard parfait, l’impossibilité de réalisation du gold standard à tous les sujets, la dépendance des résultats des tests réalisés, la variabilité de la sensibilité et/ou de la spécificité du test en fonction de certaines conditions de réalisation, la multiple réalisation du test dans le temps ou sa multiple interprétation.Une revue méthodologique systématique a été effectuée pour faire l’état des lieux des méthodes d’inférence bayésienne disponibles dans les études diagnostiques et de leur utilisation en pratique. Le focus sur les méthodes bayésiennes a été retenu du fait de leurs avantages théoriques contrastant avec leur relative sous-utilisation dans le domaine médicale. Actuellement, de nombreuses méthodes ont été proposées pour répondre à ces différentes difficultés, avec des développements très complexes en cas de combinaison de plusieurs difficultés dans une même situation. Nous avons ainsi pu établir une cartographie des combinaisons de méthodes disponibles. Cependant leur utilisation en clinique reste encore limitée, même si elle est en augmentation ces dernières années.En pratique, nous avons été confrontés à la problématique du diagnostic de pneumopathie à Pneumocystis jirovecii (PJ) (champignon ubiquitaire opportuniste responsable de mycose profonde chez les patients immunodéprimés). Dans ce projet, nous disposions des résultats de quatre techniques de PCR (Polymerase chain reaction) différentes mais sans gold standard, avec la difficulté supplémentaire de dépendance conditionnelle entre les tests du fait du principe commun à l’origine de ces quatre tests. Deux développements ont été réalisés en parallèle pour répondre à cette problématique : d’une part, un travail sur les méthodes d’élicitation des informations a priori adaptées spécifiquement aux études diagnostiques, et d’autre part, un travail de mise en œuvre d’un modèle statistique adapté à la problématique de quatre tests dépendants en l’absence de gold standard. En l’absence de données informatives dans la littérature, l’élicitation des a priori, étape obligatoire pour l’utilisation des méthodes d’inférence bayésienne, est réalisée par l’interrogation d’experts du domaine. Notre travail a consisté en une adaptation des méthodes existantes, disponibles dans le domaine des essais cliniques, spécifiquement aux études diagnostiques pour obtenir des a priori informatifs. Cette méthode a été appliquée à notre cas des PCR diagnostiques pour PJ. L’estimation des performances diagnostiques des tests en l’absence de gold standard repose de manière efficiente sur les modèles à classes latentes. Trois modèles ont été développés pour le cas de deux tests diagnostiques : un modèle à indépendance conditionnelle, un modèle à dépendance conditionnelle à effets fixes et un modèle à dépendance conditionnelle à effets aléatoires. Nous proposons dans cette thèse une adaptation de ces trois modèles à la situation de quatre tests diagnostiques avec une formulation des paramètres permettant une interprétation clinique des covariances entre les tests dans un souci de transmission des méthodes de la théorie à la pratique. Une application et une comparaison de ces modèles ont été faites pour l’estimation des sensibilités et spécificités des quatre techniques de PCR à PJ en utilisant les a priori informatifs obtenus auprès des experts. / Diagnostic studies include all clinical studies the aim of which is the evaluation of a new diagnostic test. In the evaluation process, the main step is the evaluation of the performance of the new test i.e. its sensitivity and specificity. Usually, the performance of a new test is assessed by comparison to a test of reference which is supposed to be perfect, i.e. a "gold standard", and specifies the actual patient’s status for the disease of interest (“Diseased” or “Not-Diseased” status). However, in many clinical situations, different pitfalls exist such as (i) a gold standard is not available, (ii) the gold standard is not applicable to all patients, (iii) a conditional dependence exists between test results, (iv) the performance of a test is not constant and depends on the conditions of achievement of the test, (v) the tests are repeated in time or by several machines or read by several readers, together with multiple interpretation of the results. A systematic methodological review has been performed to inventory all Bayesian inference methods available in the field of diagnostic studies and their use in practice. The focus on Bayesian methods was based on the theoretical advantages of these methods contrasting with their relative underutilization in the medical field. Finally, several interesting methods have been proposed to address methodological issues of diagnostic studies, with very complex developments when several issues were combined in the same clinical situation. We propose to map the development methods and combinations that have already been done or not. However, their clinical use is still limited, although it has increased in recent years.In practice, we met the problem of the diagnosis of pneumonia due to Pneumocystis jirovecii (PJ). PJ is an ubiquitous opportunistic fungus leading to deep mycosis in immunocompromised patients. In this study, the results of four PCR (polymerase chain reaction) assays were available, but without any gold standard, and the supplementary difficulty of conditional dependence between tests because the four tests were based on the same principle. Two works were performed in parallel to address this issue: on one hand, an adaptation of methods to elicit prior information specifically in diagnostic studies, and on the other hand, the implementation of specific Bayesian statistical models adapted to the context of four-dependent tests in the absence of gold standard. When informative information is not available in the literature, the elicitation of priors, the mandatory first step of a Bayesian inference, is carried out by registering experts’ beliefs in the field. Our work consisted in an adaptation of existing methods, available in clinical trials, specifically for diagnostic studies to obtain informative priors. We then applied this method to our four PJ PCR assays. Estimation of the diagnostic test performance in absence of gold standard is efficiently based on latent class models (LCM). Three LCM were developed for the case of two diagnostic tests: a simple LCM assuming conditional independence between tests, a fixed effects LCM and a random effects LCM providing an adjustment for conditional dependence between tests. We extended these three models to a situation where four diagnostic tests are involved and proposed a formulation that enables an interpretation of between tests covariances in a clinical perspective in order to bind theory to practice. These models were then applied and compared in an estimation study of the sensitivities and specificities of the four PJ PCR assays, by using informative priors obtained from experts.

Introduction: Mood disorders are a serious burden on Canadians. Physical and sedentary activity are easily modifiable risk factors for many diseases. An association with depression could have important implications Objective: To investigate any cross-sectional or longitudinal association between physical activity, sedentary activity, and depression in the National Longitudinal Survey of Children and Youth (NLSCY). Methods: These studies used both a stacked cross-sectional and a trajectory/latent class analysis design Univariate and multivariate multinomial logistic regressions were used to assess the relationship between physical and sedentary activity and depression using the emotional disorder-anxiety scale for children and youth available in the NLSCY. Results: When accounting for covariates, physically inactive respondents had increased odds of higher depressive symptom scores. Sedentary activity was only statistically significantly associated with depressive symptoms in the cross-sectional design. Conclusions: Physical inactivity is significantly associated to depressive symptomatology. The relationship between sedentary activity and depression is inconclusive.

Traditional latent class analysis (LCA) considers entropy R2 as the only measure of effect size. However, entropy may not always be reliable, a low boundary is not agreed upon, and good separation is limited to values of greater than .80. As applications of LCA grow in popularity, it is imperative to use additional sources to quantify LCA classification accuracy. Greater classification accuracy helps to ensure that the profile of the latent classes reflect the profile of the true underlying subgroups. This Monte Carlo study compared the quantification of classification accuracy and confidence intervals of three effect sizes, entropy R2, I-index, and Cohen’s d. Study conditions included total sample size, number of dichotomous indicators, latent class membership probabilities (γ), conditional item-response probabilities (ρ), variance ratio, sample size ratio, and distribution types for a 2-class model. Overall, entropy R2 and I-index showed the best accuracy and standard error, along with the smallest confidence interval widths. Results showed that I-index only performed well for a few cases.

Rift Valley fever (RVF) is a mosquito-borne zoonotic disease caused by a virus of the family Bunyaviridae, genus Phlebovirus. It is responsible for extensive outbreaks of disease in livestock in Africa with significant mortality and economic impact. Virus neutralization is considered the gold standard for confirming Rift Valley fever virus (RVFV) infection but the procedure is time consuming and expensive. Real-time reverse transcription-polymerase chain reaction (rRT-PCR), histopathology, and immunohistochemistry (IHC) are the diagnostic methods most often used in South Africa to confirm or exclude a diagnosis of RVF in necropsied animals. Validated estimates of diagnostic accuracy of these tests, in naturally infected livestock, however, have not been published. The objective of this study was to estimate the diagnostic sensitivity and specificity of rRT-PCR, histopathology, and IHC using Bayesian latent class methods in the absence of a gold standard. A secondary objective was to estimate stratum-specific values based on species, age, degree of specimen autolysis, and the presence/absence of tissue pigments. The Sensitivity (Se) and Specificity (Sp) of qRT-PCR were 97.4% (95% credibility interval (CI): 95.2% - 98.8%) and 71.7% (95% CI: 65% - 77.9%) respectively. The extraordinary analytical sensitivity of PCR makes this test very susceptible to false positive reactions, and thus reduced specificity. This is more likely during large-scale epidemics due to crosscontamination of specimens at necropsy facilities or testing laboratories. The Se and Sp of histopathology were 94.6% (95% CI: 91% - 97.2%) and 92.3% (95% CI: 87.6% - 95.8%) respectively. Single cases of RVF could be confused with acute poisoning with plants, bacterial septicaemias, and viral diseases such as infectious bovine rhinotracheitis and Wesselsbron disease. Most of these conditions, however, can be excluded using histological examination of the liver, special stains, bacterial culture, and toxicological or serological investigations. The Se and Sp of IHC were 97.6% (95% CI: 93.9% - 99.8%) and 99.4% (95% CI: 96.9% - 100%) respectively. Immunohistochemistry is highly specific because characteristic positive immunolabelling of the cytoplasm of hepatocytes can be correlated with the presence of hepatocellular injury typical for RVFV infection. False negative results are sometimes obtained with IHC because of reader error or loss of the antigenic epitopes due to advanced autolysis. Scant positive immunolabelling might be missed or viral proteins might be absent from sections of liver with advanced hepatocellular damage. The stratified analysis suggested differences in test accuracy in foetuses and severely autolysed specimens. The Sp of histopathology in foetuses (83.0%) was 9.3% lower than the value obtained for the sample population (92.3%). Lesions in some foetuses are more subtle and the typical eosinophilic intranuclear inclusions are often difficult to detect. In severely autolysed specimens, the Se of IHC decreased by 16.1% and the Sp of rRT-PCR by 17.4%. There is no plausible biological explanation for this decrease in the Sp of rRTPCR since the RNA of RVFV is resistant to degradation in autolysed tissues. Conversely, the antibody used to detect RVFV using IHC detects epitopes raised against nucleoproteins of the virus and it is possible that viral proteins become too widely dispersed and/or degraded in autolysed tissues to detect by light microscopy. It is possible that the marked decrease in Se of histopathology and IHC in severely autolysed specimens caused an apparent decrease in Sp of rRT-PCR, due to the latent class method. In conclusion, the high estimated Sp (99.4%) of IHC and the low Sp of rRT-PCR (71.3%) suggests that the definitive diagnosis or exclusion of RVF should not rely on a single PCR test and that IHC would be an effective confirmatory test for rRT-PCR positive field cases necropsied during an epidemic. Immunohistochemistry results from severely autolysed specimens, however, should be interpreted with caution and aborted foetuses in areas endemic for RVF should be screened using a variety of tests. The diagnostic Se and Sp of histopathology was much higher than expected confirming the value of routine post mortem examinations and histopathology of liver specimens. The most feasible RVF testing option in areas that do not have suitably equipped PCR laboratories, and where disease is often not detected in livestock until after human cases have been diagnosed, would be routine histopathology screening with IHC confirmation. Key Words: Rift Valley fever; Rift Valley fever virus; Bayesian; latent-class model; real-time reverse transcription-polymerase chain reaction; immunohistochemistry; histopathology; diagnosis; sensitivity; specificity. / Dissertation (MSc)--University of Pretoria, 2014. / gm2014 / Paraclinical Sciences / unrestricted