1,721,008 research outputs found
Assessment of channeling bias among initiators of glucose-lowering drugs: A UK cohort study [Corrigendum]
No full textAnkarfeldt MZ, Thorsted BL, Groenwold RHH, et al. Clin Epidemiol. 2017;9:19–30. On page 23, Figure 1 Notes section was marked incorrectly. The correct Notes should read as follows:Figure 1 Propensity score over time for GLP-1 versus basal insulin initiators.Notes: Blue: insulin, red: GLP-1.Abbreviation: GLP-1, glucagon-like peptide-1 analogs. On page 24, Figure 2 Notes section was marked incorrectly. The correct Notes should read as follows:Figure 2 Propensity score over time for DPP-4i versus sulfonylurea initiators.Notes: Blue: sulfonylurea, red: DPP-4i.Abbreviation: DPP-4i, dipeptidyl peptidase-4 inhibitors. On Page 3 of Supplementary materials, Figure S2 caption was shown incorrectly. The correct caption should read as follows:Figure S2 Histograms of propensity score over time. Intention-to-treat and perprotocol cohorts of all identified initiators of GLP-1 and insulin, and DPP-4i and sulfonylurea, respectively. Blue: insulin and sulfonylurea initiators, respectively. Red: GLP-1 and DPP-4i initiators, respectively. Despite the above corrections, the interpretation of these figures in the published proof and the Supplementary materials was correct. Read the original articl
Confounding and measurement error correction in epidemiological research
No full textBesides data that is primarily collected for research, in biomedical research, multiple additional sources of data, from e.g. electronic healthcare records, registries, and biobanks, are increasingly being combined into large research databases. Many are convinced of the ample opportunities this will bring for epidemiologic research, for example to study the effects of medical interventions (or treatments) and prediction of their effects. However, much of these secondary or daily care data are not collected specifically for research purposes and arise from daily practice. Here, for example, allocation of treatments is of course not a random process. As a result, obtaining valid and reliable estimates of treatment effects from these additional data sources, will crucially depend on proper consideration of methodological issues such as measurement error and confounding. Essential unanswered questions regarding both of these topics need to be addressed to reduce the risk of bias when conducting research using these additional, secondary databases. The studies presented in this thesis aimed to provide further insight on how to minimize the risk of bias when evaluating the effects of (multiple) treatments using large routine care databases. In particular, methods for confounding and measurement error adjustment were evaluated separately as well as combined. In Chapters 2 and 3 simulation studies showed that propensity score (PS) methods can be considered viable alternatives to regression based methods when adjusting for confounding in multi-treatment settings. Considering the inherent benefits of using PS methods for confounding adjustment, the findings of these two chapters suggest that these methods, and PS adjustment in particular, are appropriate alternatives to traditional logistic regression analysis when profiling many providers or comparing the effectiveness of multiple treatment options. The attention given to measurement error and its impact on estimated causal associations or the validation of clinical prediction models was discussed in Chapters 4 through 6. These three chapters demonstrate that increased awareness about the potentially important, yet often unpredictable, impact of measurement error (in covariates or predictors) is necessary. Together with additional guidance on the use of measurement error correction methods, this may stimulate researchers to account for potential measurement error in medical research. In addition, researchers should be wary that routine healthcare data may contain variables with substantial measurement error. In Chapter 7, methods were compared to adjust for a confounder (specifically disease severity) that is measured differently across centers in multicenter studies of medical treatments. In a simulation study, multiple scenarios were investigated in which the availability of different disease severity measures varied across centers depending on center level characteristics. A method based on multiple imputation of missing confounder information was most accurate in estimating the treatment effect. In Chapter 8, an existing Bayesian sample size estimation method was adapted to facilitate interim sample size re-estimations based on an estimate of the variance of the outcome. Using simulations, it was shown how this method accurately estimated the required sample size while controlling frequentist performance by employing power priors
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Defining the value of observational studies in trauma
No full textThe randomized placebo controlled trial (RCT) is considered the gold standard for clinical research. In an RCT patients are randomized between a treatment and a control group while both the patient and the physician are blinded for the treatment choice. This results in two similar and comparable groups and consequently observed differences in outcome between both groups can be ascribed to the treatment. In observational studies on treatment effect of medical interventions, there is no randomization and blinding of the patient and physician for the treatment choice is not possible. Therefore, an observational study is considered to be subject to bias and results of this type of study are considered less credible for decision making. Observational studies have an important role in reporting of adverse events, long term outcomes, and the effects of new surgical techniques. To study treatment effect, results from observational studies as compared to RCTs, are often better generalizable because of less strict inclusion criteria, have more possibilities such as subgroup analysis, and an observational study is easier, faster and less expensive to perform. These advantages make observational studies an interesting alternative for RCTs, especially in a world with fast technological advancements, continuous implementation of new techniques and limited financial possibilities. In this thesis, three types of comparisons of interventions are identified in trauma surgery with different associated types of bias influencing the observed treatment effect. Evidence is presented and substantiated which shows observational studies to produce similar treatment effects compared to RCTs. This implies research in trauma surgery can be performed more efficient, faster and with less financial funds with better generelizable results. Finally, a prospective observational study protocol is presented which aims to be a framework for future research in trauma surgery
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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