Prise en compte des hypothèses de causalité dans l'analyse d'une évolution et l'analyse de la médiation

Les travaux présentés dans ce manuscrit reposent sur un modèle structurel causal décrit par Pearl, combinant le cadre théorique des potential outcomes, les analyses du chemin et modèles d'équations structurelles, et les modèles structurels non paramétriques associés aux graphes acycliques dirigés (DAG). Dans ce modèle causal, nous nous sommes intéressés à l'analyse d'une évolution et à l'analyse de la médiation. L'estimation de l'effet causal d'une exposition (E) sur l'évolution d'un critère de jugement entre le début et la fin d'une étude se fait généralement par un modèle linéaire de l'évolution en fonction de E, ajusté ou non sur la valeur initiale du critère de jugement. Les DAG et l'analyse du chemin ont été utilisés pour représenter le schéma d'étude, les phénomènes de régression à la moyenne et l'évolution naturelle du critère de jugement dans le temps, afin de guider l'analyse dans différentes situations : (1) essais randomisés ; (2) présence de confusion entre E et le critère de jugement ; (3) valeur initiale du critère de jugement influencée par E ; (4) exposition E commençant avant le début de l'étude. Concernant l'analyse de la médiation, les performances de différentes méthodes utilisées pour calculer un effet direct contrôlé entre une exposition initiale X et un critère de jugement Y ont été évaluées dans différents scenarios simulés ainsi que dans une cohorte réelle, en présence de facteurs de confusion intermédiaires entre la variable de médiation M et le critère de jugement Y (eux-mêmes influencés par l'exposition X) : simple ajustement sur la variable de médiation M, méthode de pondération inverse, méthode séquentielle, méthode de g-computation.The work reported in this manuscript is based on a structural causal model described by Pearl as the combination of features of the potential outcome framework of Rubin, path analysis and structural equation modelling, and nonparametric structural models which can be represented by directed acyclic graphs (DAGs). We considered change from baseline analyses and mediation analyses within this structural causal model. When estimating the causal effect of an exposure of interest (E) on change from baseline, a linear regression of change on E, adjusted or unadjusted for the baseline outcome level, is usually computed. DAGs and path analysis were used to represent the design of the study, regression to the mean phenomena and the natural evolution of the outcome over time, in order to guide the statistical analysis in different situations: (i) randomized studies; (ii) confounding between the exposure and the outcome; (iii) when the observed baseline value influences the exposure; (iv) when the exposure starts before the beginning of the study. Regarding mediation analyses, we assessed the performances of different methods to estimate a controlled direct effect between an exposure X and an outcome Y, in the presence of intermediate confounding of the mediator-outcome relationship: simple adjustment for the mediator M, inverse probability of treatment weighting, the sequential g-estimator and g-computation. Estimations have been computed in several simulated data sets as well as real data from a cohort study

MRI of acute osteomyelitis in long bones of children: pathophysiology study.

INTRODUCTION: The classic pathophysiology of acute osteomyelitis in children described by Trueta has a metaphyseal infection as the starting point. This hypothesis was recently brought into question by Labbé's study, which suggested a periosteal origin. Thus, we wanted to study this disease's pathophysiology through early MRI examinations and to look for prognostic factors based on abnormal findings. MATERIAL AND METHODS: This was a prospective, multicentre study that included cases of long bone osteomyelitis in children who underwent an MRI examination within 7days of the start of symptoms and within 24hours of the initiation of antibiotic therapy. We also collected clinical, laboratory and treatment-related data. RESULTS: Twenty patients were included, including one with a bifocal condition. The lower limb was involved in most cases (19/21). Staphylococcus aureus was found most frequently. Metaphyseal involvement was present in all cases. No isolated periosteal involvement was found in any of the cases. No prognostic factors were identified based on the various abnormal findings on MRI. CONCLUSION: Our study supports the metaphyseal origin of acute osteomyelitis in children. LEVEL OF EVIDENCE:II

Correction: Primary and predicted secondary structure of the actinomadura R39 extracellular DD-peptidase, a penicillin-binding protein (PBP) related to the escherichia coli PBP4 (Biochemical Journal(1992)282(786))

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HQET at order 1/m1/m: II. Spectroscopy in the quenched approximation

Using Heavy Quark Effective Theory with non-perturbatively determined parameters in a quenched lattice calculation, we evaluate the splittings between the ground state and the first two radially excited states of the $B_s$ system at static order. We also determine the splitting between first excited and ground state, and between the $B_s^*$ and $B_s$ ground states to order $1/m_b$. The Generalized Eigenvalue Problem and the use of all-to-all propagators are important ingredients of our approach.Comment: (1+18) pages, 3 figures (4 pdf files); pdflatex; v2: corrections to table 1, results unaffecte

SRH and HrQOL: does social position impact differently on their link with health status?

<p>Abstract</p> <p>Background</p> <p>Self-rated Health (SRH) and health-related quality of life (HRQoL) are used to evaluate health disparities. Like all subjective measures of health, they are dependent on health expectations that are associated with socioeconomic characteristics. It is thus needed to analyse the influence played by socioeconomic position (SEP) on the relationship between these two indicators and health conditions if we aim to use them to study health disparities. Our objective is to assess the influence of SEP on the relationship between physical health status and subjective health status, measured by SRH and HRQoL using the SF-36 scale.</p> <p>Methods</p> <p>We used data from the French National Health Survey. SEP was assessed by years of education and household annual income. Physical health status was measured by functional limitations and chronic low back pain.</p> <p>Results</p> <p>Regardless of their health status, people with lower SEP were more likely than their more socially advantaged counterparts to report poor SRH and poorer HRQoL, using any of the indicators of SEP. The negative impact of chronic low back pain on SRH was relatively greater in people with a high SEP than in those with a low SEP. In contrast, chronic low back pain and functional limitations had less impact on physical and mental component scores of quality of life for socially advantaged men and women.</p> <p>Conclusions</p> <p>Both SRH and HRQoL were lower among those reporting functional limitations or chronic low back pain. However, the change varied according SEP and the measure. In relative term, the negative impact of a given health condition seems to be greater on SRH and lower on HRQoL for people with higher SEP in comparison with people with low SEP. Using SRH could thus decrease socioeconomic differences. In contrast using HRQoL could increase these differences, suggesting being cautious when using these indicators for analyzing health disparities.</p

Pandemic A/H1N1v influenza 2009 in hospitalized children: a multicenter Belgian survey

<p>Abstract</p> <p>Background</p> <p>During the 2009 influenza A/H1N1v pandemic, children were identified as a specific "at risk" group. We conducted a multicentric study to describe pattern of influenza A/H1N1v infection among hospitalized children in Brussels, Belgium.</p> <p>Methods</p> <p>From July 1, 2009, to January 31, 2010, we collected epidemiological and clinical data of all proven (positive H1N1v PCR) and probable (positive influenza A antigen or culture) pediatric cases of influenza A/H1N1v infections, hospitalized in four tertiary centers.</p> <p>Results</p> <p>During the epidemic period, an excess of 18% of pediatric outpatients and emergency department visits was registered. 215 children were hospitalized with proven/probable influenza A/H1N1v infection. Median age was 31 months. 47% had ≥ 1 comorbid conditions. Febrile respiratory illness was the most common presentation. 36% presented with initial gastrointestinal symptoms and 10% with neurological manifestations. 34% had pneumonia. Only 24% of the patients received oseltamivir but 57% received antibiotics. 10% of children were admitted to PICU, seven of whom with ARDS. Case fatality-rate was 5/215 (2%), concerning only children suffering from chronic neurological disorders. Children over 2 years of age showed a higher propensity to be admitted to PICU (16% vs 1%, p = 0.002) and a higher mortality rate (4% vs 0%, p = 0.06). Infants less than 3 months old showed a milder course of infection, with few respiratory and neurological complications.</p> <p>Conclusion</p> <p>Although influenza A/H1N1v infections were generally self-limited, pediatric burden of disease was significant. Compared to other countries experiencing different health care systems, our Belgian cohort was younger and received less frequently antiviral therapy; disease course and mortality were however similar.</p

On the Functional Significance of the P1 and N1 Effects to Illusory Figures in the Notch Mode of Presentation

The processing of Kanizsa figures have classically been studied by flashing the full “pacmen” inducers at stimulus onset. A recent study, however, has shown that it is advantageous to present illusory figures in the “notch” mode of presentation, that is by leaving the round inducers on screen at all times and by removing the inward-oriented notches delineating the illusory figure at stimulus onset. Indeed, using the notch mode of presentation, novel P1and N1 effects have been found when comparing visual potentials (VEPs) evoked by an illusory figure and the VEPs to a control figure whose onset corresponds to the removal of outward-oriented notches, which prevents their integration into one delineated form. In Experiment 1, we replicated these findings, the illusory figure was found to evoke a larger P1 and a smaller N1 than its control. In Experiment 2, real grey squares were placed over the notches so that one condition, that with inward-oriented notches, shows a large central grey square and the other condition, that with outward-oriented notches, shows four unconnected smaller grey squares. In response to these “real” figures, no P1 effect was found but a N1 effect comparable to the one obtained with illusory figures was observed. Taken together, these results suggest that the P1 effect observed with illusory figures is likely specific to the processing of the illusory features of the figures. Conversely, the fact that the N1 effect was also obtained with real figures indicates that this effect may be due to more global processes related to depth segmentation or surface/object perception

A first update on mapping the human genetic architecture of COVID-19

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Rôle du contexte géographique et social sur la précocité d'accès au diagnostic de démence en consultation mémoire (étude d'une population de patients vus en consultation mémoire dans trois hôpitaux de la région Poitou-Charentes)

POITIERS-BU Médecine pharmacie (861942103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF