Volunteer Bias in Recruitment, Retention, and Blood Sample Donation in a Randomised Controlled Trial Involving Mothers and Their Children at Six Months and Two Years: A Longitudinal Analysis

BACKGROUND: The vulnerability of clinical trials to volunteer bias is under-reported. Volunteer bias is systematic error due to differences between those who choose to participate in studies and those who do not. METHODS AND RESULTS: This paper extends the applications of the concept of volunteer bias by using data from a trial of probiotic supplementation for childhood atopy in healthy dyads to explore 1) differences between a) trial participants and aggregated data from publicly available databases b) participants and non-participants as the trial progressed 2) impact on trial findings of weighting data according to deprivation (Townsend) fifths in the sample and target populations. 1) a) Recruits (n = 454) were less deprived than the target population, matched for area of residence and delivery dates (n = 6,893) (mean [SD] deprivation scores 0.09[4.21] and 0.79[4.08], t = 3.44, df = 511, p<0.001). b) i) As the trial progressed, representation of the most deprived decreased. These participants and smokers were less likely to be retained at 6 months (n = 430[95%]) (OR 0.29,0.13-0.67 and 0.20,0.09-0.46), and 2 years (n = 380[84%]) (aOR 0.68,0.50-0.93 and 0.55,0.28-1.09), and consent to infant blood sample donation (n = 220[48%]) (aOR 0.72,0.57-0.92 and 0.43,0.22-0.83). ii) Mothers interested in probiotics or research or reporting infants' adverse events or rashes were more likely to attend research clinics and consent to skin-prick testing. Mothers participating to help children were more likely to consent to infant blood sample donation. 2) In one trial outcome, atopic eczema, the intervention had a positive effect only in the over-represented, least deprived group. Here, data weighting attenuated risk reduction from 6.9%(0.9-13.1%) to 4.6%(-1.4-+10.5%), and OR from 0.40(0.18-0.91) to 0.56(0.26-1.21). Other findings were unchanged. CONCLUSIONS: Potential for volunteer bias intensified during the trial, due to non-participation of the most deprived and smokers. However, these were not the only predictors of non-participation. Data weighting quantified volunteer bias and modified one important trial outcome. TRIAL REGISTRATION: This randomised, double blind, parallel group, placebo controlled trial is registered with the International Standard Randomised Controlled Trials Register, Number (ISRCTN) 26287422. Registered title: Probiotics in the prevention of atopy in infants and children

Studying Networks Geographically: World Political Regionalization in the United Nations General Assembly (1985–2010)

International audienceThe study of networks from the viewpoint of a geographer does not mean studying geographical networks as technical infrastructures, especially when one is interested in geopolitical phenomena. It means that the relational nature of a given spatial phenomenon seems to demand a specific approach, that is, a network one, and that formalization via a graph (a set of nodes, a set of links between these nodes, and some attributes) allows discovering unrevealed aspects of a sociospatial fact. The study of networks often means adopting an interdisciplinary posture, applying tools and methods developed in other academic fields, and conducting solid conceptual analysis. For instance, whereas distance and centrality are useful concepts in both geography and social network analysis, their definition and implications for research remain quite different and need to be adapted from one academic field to another to remain efficient and relevant. This chapter presents results on the political regionalization process on a world scale, a process understood as the reinforcement of supranational structures based on geographical proximity. I presume that political actors, and especially state representatives in intergovernmental organizations, are constrained to work more and more often supranationally because of the globalization process, a process that can be understood neither solely nor primarily as an economic or financial phenomenon but rather as an increase in global issues demanding global responses and a gover-nance shift (e.g., global warming, migrations, and energy). Although much has been published on economic regionalization since the 1990s (e.g., Mansfield & Milner, 1999), the political aspects have been quite neglected, and when they are studied, especially in international relations, the approach is mainly qualitative and purely conceptual (Barnett & Duvall, 2005; Diehl, 2005). The approach investigated in this chapter is taken from the behavioral school of international relations: If political regionalization is occurring, it should be possible to measure it, produce indicators

Acesso à assistência oncológica: mapeamento dos fluxos origem-destino das internações e dos atendimentos ambulatoriais. O caso do câncer de mama Access to cancer care: mapping hospital admissions and high-complexity outpatient care flows. The case of breast cancer

Este estudo analisa o fluxo de pacientes atendidas com câncer de mama, no Brasil, no âmbito do SUS, segundo o tipo de tratamento recebido. Foram identificadas redes de atenção oncológica com base nas informações do Sistema de Informações Hospitalares e do Sistema Informações Ambulatoriais de Alta Complexidade em Oncologia, relativas ao período 2005-2006, utilizando os programas TabWin e TerraView. O atendimento está amplamente distribuído pelo território nacional, com forte concentração nos maiores centros, e indícios de escassez de atendimento mesmo nas regiões onde a oferta de serviços é maior. Grande proporção das pacientes reside a mais de 150km do local de atendimento. A identificação das redes constitui ferramenta com aplicação importante no planejamento e na melhoria da distribuição dos serviços, considerando que o acesso geográfico é relevante para o desfecho do tratamento. A redução das taxas de morbidade e mortalidade depende da identificação precoce, pois, uma vez identificado o caso, o tratamento adequado e ágil concorre para reduzir os impactos da doença.<br>This study analyzes the flow of patients with breast cancer treated in Brazil's Unified National Health System (SUS) by type of treatment (surgery, radiotherapy, and chemotherapy). Hospital and outpatient services networks were identified based on data from the National Information System for Inpatient Care (SIH), and the National Information System for Outpatient Cancer Care, for 2005-2006, using TabWin and TerraView. Health services networks reach most of the country, and few municipalities are not connected to a network. However, treatment is highly concentrated in the largest cities, and even the latter show evidence of service shortages. Furthermore, a large proportion of patients live more than 150km from the respective service. Network identification is important for planning and improving services distribution, since geographic access is a relevant issue for treatment outcome. Reduction of morbidity and mortality requires early identification, and appropriate and prompt treatment can reduce the impacts of the disease

DNA pooling: A tool for large-scale association studies

DNA pooling is a practical way to reduce the cost of large-scale association studies to identify susceptibility loci for common diseases. Pooling allows allele frequencies in groups of individuals to be measured using far fewer PCR reactions and genotyping assays than are used when genotyping individuals. Here, we discuss recent developments in quantitative genotyping assays and in the design and analysis of pooling studies. Sophisticated pooling designs are being developed that can take account of hidden population stratification, confounders and inter-loci interactions, and that allow the analysis of haplotypes.link_to_subscribed_fulltex