1,721,055 research outputs found
Graphical sensitivity analysis with different methods of imputation for a trial with probable non-ignorable missing data
No full textGraphical sensitivity analyses have recently been recommended for clinical trials with non-ignorable missing binary outcome. We demonstrate an adaptation of this methodology for a continuous outcome of a trial of three cognitive-behavioural therapies for mild depression in primary care, in which one arm had unexpectedly high levels of missing data. Fixed value and multiple imputation from a normal distribution (assuming either varying mean and fixed SD, or fixed mean and varying SD) were used to obtain contour plots of the contrast estimates with their P values superimposed; their confidence interval; and the root mean square error. Imputation was based on both the outcome value alone, or on change from baseline. The plots showed fixed value imputation to be more sensitive than imputing from a normal distribution, but the normally distributed imputations were subject to sampling noise. The contours of the sensitivity plots were close to linear in appearance with the slope approximately equal to the ratio of the proportions of subjects with missing data in each trial arm
The analysis of continuous outcomes in multi-centre trials with small centre sizes
No full textThe standard analysis of clinical trials stratified by centre is to include centres as fixed effects, but if many centres contribute small numbers of patients, this approach results in a loss of power. Assuming no treatment by centre interaction, we used simulation to examine power and coverage of confidence intervals from three approaches to the analysis of continuous outcome in multi-centre trials: ignoring centres, including centres as fixed effects, and including them as random effects. The simulation incorporated eight sizes of centre effects; randomization in blocks of size 2 or 4; and two sample sizes, namely 100 and 200 patients per treatment arm in a parallel groups design. All simulated data sets included many centres with few subjects. The three different approaches were unbiased and had similar coverage. Fixed effects analysis was less powerful, particularly when centre effects were small. Incorporating block randomization with larger block size increased non-orthogonality in the design, contributing to loss of power. Where centre effects are small and recruitment in many centres is low, the approaches of ignoring centres or incorporating them as random effects have better performance than the traditional fixed effects analysis
Relationship between process and outcome in stroke care
No full textBackground and Purpose: Better processes in stroke care are assumed to lead to better stroke outcomes. We sought to test whether current measures of stroke process are related to measures of stroke outcome.Methods: This was a prospective study of consecutive patients with acute stroke admitted to each of the 3 general hospitals in 1 region who were followed up for 12 months after hospital discharge. Process was measured by use of the Royal College of Physicians Stroke Audit Package, and outcomes were measured with a range of disability, health status, handicap, and independence measures, as well as mortality.Results: One hundred eighty-one patients were recruited. There was evidence for a relationship between some process variables and outcomes at hospital discharge, but the relationships were generally weak. None of the process variables remained in regression models of functional outcomes at 12 months. The hospital with the best process scores had the worst case mix-adjusted outcomes.Conclusions: The link between stroke process and outcome, through the use of currently available measures of process such as the Royal College of Physicians Stroke Audit Package, is not straightforward. Ongoing work may clarify some of these issues and provide guidance to stroke clinicians on how best to improve existing services
Self-valuation and societal valuations of health state differ with disease severity in chronic and disabling conditions
No full textObjectives: We sought to determine the relationship between self-reported ratings of health-related quality of life (HRQoL) by people with 3 chronic and disabling conditions and population estimates of those health states and to model factors that might explain the disagreement between these 2 ratings. Research Design: A cross-sectional postal survey was sent in which each participant completed a set of questionnaires addressing HRQoL. Data from self-valuation on a visual analog scale (VAS) was compared with a population-based VAS-equivalent valuation, using the EQ-5D instrument. Different ways of scaling the 2 VAS scores were also explored. Data were analyzed using descriptive statistics and analysis of covariance. Subjects: A community sample of 1036 people took part in the study (rheumatoid arthritis n = 142, stroke n = 585, multiple sclerosis n = 309). Measurement instrument: The EQ-5D health state profile and accompanying visual analog scale were used.Results: Self-ratings were significantly different than the population-based ratings, and agreement was poor, both on the original scale of the data and by analyses of rescaled data. On the original scales the mean difference was 0.13 (95% confidence interval 0.117-0.143). Diagnosis, health state severity, and its square explained 35.3% of the variation in the differences between self and population ratings with a curvilinear relationship suggesting that the differences increased as the health state worsened, but at a decreasing rate as health state severity increased.Conclusions: This study provides evidence that EQ-5D population valuation estimates of treatment benefit for people with disabling and chronic conditions may well be inaccurate representations of the degree of change actually experienced by the individual with the condition. The varying magnitude of difference between the 2 forms of valuation has important implications for interpreting shifts in health status valuation following interventions for these populations
Community ambulation after stroke: how important and obtainable is it an what measures appear predictive?
No full textOBJECTIVES: To assess how important community ambulation is to stroke survivors and to assess the relation between the level of community ambulation achieved and other aspects of mobility.DESIGN: A multicenter observational survey.SETTING: Community setting in New Zealand.PARTICIPANTS: One hundred fifteen stroke survivors living at home were referred from physical therapy (PT) services at 3 regional hospitals at the time of discharge and were assessed within 1 week after returning home. Another 15 people with stroke who did not require further PT when discharged were assessed within 2 weeks after they returned home to provide insight into community ambulation status for those without mobility impairment, as recognized by health professionals.INTERVENTIONS: Not applicable.MAIN OUTCOME MEASURES: Self-reported levels of community ambulation ascertained by questionnaire, gait velocity (m/min), Functional Ambulation Categories (FAC) score, and Rivermead Mobility Index (RMI) score.RESULTS: Mean gait velocity for the participants was 53.9 m/min (95% confidence interval [CI], 52.3-61.1) mean treadmill distance was 165.5 m (95% CI, 141.6-189.5); median RMI score was 14; and median FAC score was 6. Mobility scores for the 15 people who did not require PT were within the normal range. Based on self-reported levels of ambulation, 19 (14.6%) participants were unable to leave the home unsupervised, 22 (16.9%) were walking as far as the letterbox, 10 (7.6%) were limited to walking within their immediate environment, and 79 (60.7%) could access shopping malls and/or places of interest. Participants with different levels of community ambulation showed a significant difference in gait velocity (P<.001). The ability to "get out and about" in the community was considered to be either essential or very important by 97 subjects (74.6%). CONCLUSIONS: Community ambulation is a meaningful outcome after stroke. However, despite good mobility outcomes on standardized measures for this cohort of home-dwelling stroke survivors, nearly one third were not getting out unsupervised in the community. Furthermore, gait velocity may be a measure that discriminates between different categories of community ambulation. These findings may have implications for PT practice for people with mobility problems after stroke
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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