131,891 research outputs found
Comment on 'The latency period of mesothelioma among a cohort of British asbestos workers (1978-2005)': methodological problems with case-only survival analysis.
No full textObjective Bayesian search of Gaussian directed acyclic graphical models for ordered variables with non-local priors
No full textDirected acyclic graphical (DAG) models are increasingly employed in the study of physical and biological systems
to model direct influences between variables. Identifying the graph from data is a challenging endeavor, which can be more
reasonably tackled if the variables are assumed to satisfy a given ordering; in this case we simply have to estimate the presence
or absence of each potential edge. Working under this assumption, we propose an objective Bayesian method for searching the
space of Gaussian DAG models, which provides a rich output from minimal input.We base our analysis on non-local parameter
priors, which are especially suited for learning sparse graphs, because they allow a faster learning rate, relative to ordinary
local parameter priors, when the true unknown sampling distribution belongs to a simple model. We implement an efficient
stochastic search algorithm, which deals effectively with data sets having sample size smaller than the number of variables,
and apply our method to a variety of simulated and real data sets. Our approach compares favorably, in terms of the ROC
curve for edge hit rate versus false alarm rate, to current state-of-the-art frequentist methods relying on the assumption of
ordered variables; under this assumption it exhibits a competitive advantage over the PC-algorithm, which can be considered
as a frequentist benchmark for unordered variables. Importantly, we find that our method is still at an advantage for learning
the skeleton of the DAG, when the ordering of the variables is only moderately mis-specified. Prospectively, our method could
be coupled with a strategy to learn the order of the variables, thus dropping the known ordering assumption
Enhanced objective Bayesian testing for the equality of two proportions
No full textWe develop a new class of prior distributions for Bayesian comparison of nested models, which we call intrinsic moment priors, by combining the well-established notion of intrinsic prior with the recently introduced idea of non-local priors, and in particular of moment priors. Specifically, we aim at testing the equality of two proportions, based on independent samples, and thus focus on discrete data models. Given two nested models, each equipped with a default prior, we first construct a moment prior under the larger model. In this way, the asymptotic learning behavior of the Bayes factor is strengthened, relative to currently used local priors, when the smaller model holds; remarkably, this effect is already apparent for moderate sample sizes. On the other hand, the symptotic learning behavior of the Bayes factor when the larger model holds is unchanged. However, without appropriate tuning, a moment prior does not provide enough evidence for the larger model when the sample size is small and the data only moderately support the smaller one. For this reason, we apply to the moment prior an intrinsic prior procedure, which amounts to pulling the moment prior towards the subspace specified by the smaller model; we provide general guidelines for determining the training sample size necessary to implement this step. Thus, by joining the virtues of moment and intrinsic priors, we obtain an enhanced objective Bayesian testing procedure: i) our evidence for small samples is broadly comparable to that given by current objective methods; ii) we achieve a superior learning performance as the sample size increases (when the smaller model holds). We first illustrate our methodology in a running Bernoulli example, where we test a sharp null hypothesis, then we implement our procedure to test the equality of two proportions. A detailed analysis of the properties of our method, including a comparison with standard intrinsic priors, is presented together with an application to a collection of real-world 2 by 2 tables involving a sensitivity analysis and a crossvalidation study.<br/
Determinants of Seeking Treatment for Cocaine Abuse: A Case-Control Study
No full textThe objective of this study, which targeted long-term socially integrated cocaine users (in powder form, no heroin), was to analyze potential determinants of request for treatment for primary cocaine abuse. Two hundred and twenty-three cases (users who sought treatment for primary cocaine abuse) and 223 controls (users who did not seek treatment) were interviewed in Italy. A semistructured interview was created. Conditional logistic regression models were used. Cases had begun consuming illicit substances later, started using cocaine quicker, had high-risk drinking habits, had more intense recent use of cocaine, and used alone and at work. Some of the motivations of use that characterize subjects who seek treatment (to experience a 'high', disinhibition, avoidance, and to feel more confident) seem specifically to obtain immediate gratification, without concern for future consequences. Variability in cocaine abusers seeking treatment has been a long-recognized feature of this population and the results show that the appropriate target population (cocaine users experiencing problems and using more frequently) is reached by treatment services
Noninvasive ventilation in chest trauma: Systematic review and meta-analysis
No full textPurpose: Single studies of Noninvasive Ventilation (NIV) in the management of acute respiratory failure in chest trauma patients have produced controversial findings. The aim of this study is to critically review the literature to investigate whether NIV reduces mortality, intubation rate, length of stay and complications in patients with chest trauma, compared to standard therapy. Methods: We performed a systematic review and meta-analysis of randomized controlled trials, prospective and retrospective observational studies, by searching PubMed, EMBASE and bibliographies of articles retrieved. We screened for relevance studies that enrolled adults with chest trauma who developed mild to severe acute respiratory failure and were treated with NIV. We included studies reporting at least one clinical outcome of interest to perform a meta-analysis. Results: Ten studies (368 patients) met the inclusion criteria and were included for the meta-analysis. Five studies (219 patients) reported mortality and results were quite homogeneous across studies, with a summary relative risk for patients treated with NIV compared with standard care (oxygen therapy and invasive mechanical ventilation) of 0.26 (95 % confidence interval 0.09-0.71, p = 0.003). There was no advantage in mortality of continuous positive airway pressure over noninvasive pressure support ventilation. NIV significantly increased arterial oxygenation and was associated with a significant reduction in intubation rate, in the incidence of overall complications and infections. Conclusions: These results suggest that NIV could be useful in the management of acute respiratory failure due to chest trauma. © 2013 Springer-Verlag Berlin Heidelberg and ESICM
Diagnosi precoce del cancro del polmone in lavoratori esposti a cancerogeni
No full textFollowing the publication of results of NLST (National Lung Screening Trial, USA) and ELCAP (Early Lung Cancer Action Project, USA), lung cancer screening with low-dose computed tomography (LDCT) in high-risk subjects has been recommended in North-America. Conversely, the European Community has been waiting for further evidence. The recently concluded Dutch-Belgian Lung Cancer Screening trial (NELSON) confirmed the efficacy of LDCT screening in reducing lung cancer mortality. Two recent studies in the USA and Italy showed positive results in occupational settings among workers formerly exposed to asbestos. The available evidence seems to suggest the need to implement lung cancer screening programs among heavy smokers and workers substantively exposed to occupational carcinogens also in Europe, following common, standardized procedures, as indicated in a recent European position statement
Historical Trend of Exposure to Perfluoroalkyl Surfactants PFOA, ADV, and cC6O4 and its Management in Two Perfluoroalkyl Polymers Plants, Italy
No full textObjectives Perfluoroalkyl acid surfactants are used in the chemical industry for the synthesis of perfluoroalkyl polymers. In one Italian fluoropolymer plant and in the research and innovation center, two major perfluoroalkyl surfactants have been historically used: PFOA and ADV and a third, cC(6)O(4) substituted PFOA from mid-2013. This work is summarizing occupational exposure to these chemicals in the period 2004-2021, assessed by biological monitoring. Moreover, taking advantage of the phasing out of PFOA, the elimination kinetics of PFOA in humans is investigated. Methods Workers exposed to PFOA (from beginning of the sixties to 2013), ADV (since 1996), and/or cC(6)O(4) (since 2012) in the production of fluoropolymers, in the synthesis, research, and analysis, were periodically surveyed from 2004, measuring the concentration of perfluoroalkyl acid surfactants in serum. Workers of the same plants, not directly exposed, were surveyed as well. Applying the first-order kinetics model, the half-life of PFOA was calculated. Results 809 Workers were investigated with measurements of PFOA (n = 3692), ADV (n = 4288) and cC(6)O(4) (n = 2272) in serum. In the production plant, median PFOA ranged from 1900 to 14 mu g/l from 2004 to 2021; median ADV ranged from 434 to 86 mu g/l from 2011 to 2021. For cC(6)O(4) the detection percentage ranged from 9 to 47%; in detected samples median cC(6)O(4) ranged from 3 to 16 mu g/l in the period 2013-2021. Adopted mitigation measurements included: the phasing out of PFOA, the improvement of the plastomer and elastomer post-treatments; the reinforcement of the staff involved in prevention. Decreasing trends were observed for all chemicals along years (P value for linear trend of means < 0.01). For PFOA, a half-life of 3.16 (95% CI 2.98-3.37) years was calculated. Conclusions In the study plants, several initiatives to reduce exposure and the risk associated with perfluoroalkyl surfactants were undertaken; results of biomonitoring show that they were effective, with a 5- to 136-fold reduction in the concentration of perfluoroalkyl compounds in the serum of workers
Rapid drink challenge and multiple rapid swallowing : Reproducibility of esophageal function assessment
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