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Research Synthesis Methods

Michael Borenstein, Julian P T Higgins, Larry V Hedges, Hannah R Rothstein
No abstract text is available yet for this article.
June 20, 2017: Research Synthesis Methods
David C Hoaglin
No abstract text is available yet for this article.
June 20, 2017: Research Synthesis Methods
François Curtin
Clinical trials have different designs: In late stage drug development, the parallel trial design is the most frequent one; however, the crossover design is not rare; different techniques are used to analyse their results. Although both designs measure the same treatment effect, combining parallel and crossover trials in a meta-analysis is not straightforward. We present here a meta-analysis method based on generalised estimating equation (GEE) regression to combine aggregated results of crossover and parallel trials using a marginal estimation approach...
June 5, 2017: Research Synthesis Methods
Dan Jackson, Areti Angeliki Veroniki, Martin Law, Andrea C Tricco, Rose Baker
Network meta-analysis is used to simultaneously compare multiple treatments in a single analysis. However, network meta-analyses may exhibit inconsistency, where direct and different forms of indirect evidence are not in agreement with each other, even after allowing for between-study heterogeneity. Models for network meta-analysis with random inconsistency effects have the dual aim of allowing for inconsistencies and estimating average treatment effects across the whole network. To date, two classical estimation methods for fitting this type of model have been developed: a method of moments that extends DerSimonian and Laird's univariate method and maximum likelihood estimation...
June 5, 2017: Research Synthesis Methods
José Antonio López-López, Wim Van den Noortgate, Emily E Tanner-Smith, Sandra Jo Wilson, Mark W Lipsey
Dependent effect sizes are ubiquitous in meta-analysis. Using Monte Carlo simulation, we compared the performance of 2 methods for meta-regression with dependent effect sizes-robust variance estimation (RVE) and 3-level modeling-with the standard meta-analytic method for independent effect sizes. We further compared bias-reduced linearization and jackknife estimators as small-sample adjustments for RVE and Wald-type and likelihood ratio tests for 3-level models. The bias in the slope estimates, width of the confidence intervals around those estimates, and empirical type I error and statistical power rates of the hypothesis tests from these different methods were compared for mixed-effects meta-regression analysis with one moderator either at the study or at the effect size level...
May 28, 2017: Research Synthesis Methods
Xuanqian Xie, Alison Sinclair, Nandini Dendukuri
BACKGROUND: Streptococcus pneumoniae (SP) pneumonia is often treated empirically as diagnosis is challenging because of the lack of a perfect test. Using BinaxNOW-SP, a urinary antigen test, as an add-on to standard cultures may not only increase diagnostic yield but also increase costs. OBJECTIVE: To estimate the sensitivity and specificity of BinaxNOW-SP and subsequently estimate the cost-effectiveness of adding BinaxNOW-SP to the diagnostic work-up. DESIGN: We fit a Bayesian latent-class meta-analysis model to obtain estimates of BinaxNOW-SP accuracy that adjust for the imperfect accuracy of culture...
May 23, 2017: Research Synthesis Methods
Thomas R Fanshawe, Luke F Shaw, Graeme T Spence
INTRODUCTION: Previous studies suggest that many systematic reviews contain meta-analyses that display temporal trends, such as the first study's result being more extreme than later studies' or a drift in the pooled estimate. We assessed the extent and characteristics of temporal trends using all Cochrane intervention reports published 2008-2012. METHODS: We selected the largest meta-analysis within each report and analysed trends using methods including a Z-test (first versus subsequent estimates); generalised least squares; and cumulative sum charts...
May 11, 2017: Research Synthesis Methods
Sean Harrison, Hayley E Jones, Richard M Martin, Sarah J Lewis, Julian P T Higgins
Meta-analyses combine the results of multiple studies of a common question. Approaches based on effect size estimates from each study are generally regarded as the most informative. However, these methods can only be used if comparable effect sizes can be computed from each study, and this may not be the case due to variation in how the studies were done or limitations in how their results were reported. Other methods, such as vote counting, are then used to summarize the results of these studies, but most of these methods are limited in that they do not provide any indication of the magnitude of effect...
April 28, 2017: Research Synthesis Methods
François Curtin
Meta-analysis can necessitate the combination of parallel and cross-over trial designs. Because of the differences in the trial designs and potential biases notably associated with the crossover trials, one often combines trials of the same designs only, which decreases the power of the meta-analysis. To combine results of clinical trials from parallel and cross-over designs, we extend the method proposed in an accompanying study to account for random effects. We propose here a hierarchical mixed model allowing the combination of the 2 types of trial designs and accounting for additional covariates where random effects can be introduced to account for heterogeneity in trial, treatment effect, and interactions...
April 21, 2017: Research Synthesis Methods
Leonie van Grootel, Floryt van Wesel, Alison O'Mara-Eves, James Thomas, Joop Hox, Hennie Boeije
BACKGROUND: This study describes an approach for the use of a specific type of qualitative evidence synthesis in the matrix approach, a mixed studies reviewing method. The matrix approach compares quantitative and qualitative data on the review level by juxtaposing concrete recommendations from the qualitative evidence synthesis against interventions in primary quantitative studies. However, types of qualitative evidence syntheses that are associated with theory building generate theoretical models instead of recommendations...
April 21, 2017: Research Synthesis Methods
Dan Jackson, Rebecca Turner
One of the reasons for the popularity of meta-analysis is the notion that these analyses will possess more power to detect effects than individual studies. This is inevitably the case under a fixed-effect model. However, the inclusion of the between-study variance in the random-effects model, and the need to estimate this parameter, can have unfortunate implications for this power. We develop methods for assessing the power of random-effects meta-analyses, and the average power of the individual studies that contribute to meta-analyses, so that these powers can be compared...
April 4, 2017: Research Synthesis Methods
Hanna Olofsson, Agneta Brolund, Christel Hellberg, Rebecca Silverstein, Karin Stenström, Marie Österberg, Jessica Dagerhamn
BACKGROUND: One time-consuming aspect of conducting systematic reviews is the task of sifting through abstracts to identify relevant studies. One promising approach for reducing this burden uses text mining technology to identify those abstracts that are potentially most relevant for a project, allowing those abstracts to be screened first. OBJECTIVES: To examine the effectiveness of the text mining functionality of the abstract screening tool Rayyan. User experiences were collected...
April 4, 2017: Research Synthesis Methods
Mi-Ok Kim, Xia Wang, Chunyan Liu, Kathleen Dorris, Maryam Fouladi, Seongho Song
Phase I trials aim to establish appropriate clinical and statistical parameters to guide future clinical trials. With individual trials typically underpowered, systematic reviews and meta-analysis are desired to assess the totality of evidence. A high percentage of zero or missing outcomes often complicate such efforts. We use a systematic review of pediatric phase I oncology trials as an example and illustrate the utility of advanced Bayesian analysis. Standard random-effects methods rely on the exchangeability of individual trial effects, typically assuming that a common normal distribution sufficiently describes random variation among the trial level effects...
June 2017: Research Synthesis Methods
Simon Briscoe, Chris Cooper, Julie Glanville, Carol Lefebvre
No abstract text is available yet for this article.
March 7, 2017: Research Synthesis Methods
Brittany U Burda, Elizabeth A O'Connor, Elizabeth M Webber, Nadia Redmond, Leslie A Perdue
BACKGROUND: Systematic reviewers often encounter incomplete or missing data, and the information desired may be difficult to obtain from a study author. Thus, systematic reviewers may have to resort to estimating data from figures with little or no raw data in a study's corresponding text or tables. METHODS: We discuss a case study in which participants used a publically available Web-based program, called webplotdigitizer, to estimate data from 2 figures. We evaluated and used the intraclass coefficient and the accuracy of the estimates to the true data to inform considerations when using estimated data from figures in systematic reviews...
March 7, 2017: Research Synthesis Methods
Michael Borenstein, Julian P T Higgins, Larry V Hedges, Hannah R Rothstein
When we speak about heterogeneity in a meta-analysis, our intent is usually to understand the substantive implications of the heterogeneity. If an intervention yields a mean effect size of 50 points, we want to know if the effect size in different populations varies from 40 to 60, or from 10 to 90, because this speaks to the potential utility of the intervention. While there is a common belief that the I(2) statistic provides this information, it actually does not. In this example, if we are told that I(2) is 50%, we have no way of knowing if the effects range from 40 to 60, or from 10 to 90, or across some other range...
March 2017: Research Synthesis Methods
G J Melendez-Torres, A O'Mara-Eves, J Thomas, G Brunton, J Caird, M Petticrew
Using Toulmin's argumentation theory, we analysed the texts of systematic reviews in the area of workplace health promotion to explore differences in the modes of reasoning embedded in reports of narrative synthesis as compared with reports of meta-analysis. We used framework synthesis, grounded theory and cross-case analysis methods to analyse 85 systematic reviews addressing intervention effectiveness in workplace health promotion. Two core categories, or 'modes of reasoning', emerged to frame the contrast between narrative synthesis and meta-analysis: practical-configurational reasoning in narrative synthesis ('what is going on here? What picture emerges?') and inferential-predictive reasoning in meta-analysis ('does it work, and how well? Will it work again?')...
March 2017: Research Synthesis Methods
Tim Friede, Christian Röver, Simon Wandel, Beat Neuenschwander
Meta-analyses in orphan diseases and small populations generally face particular problems, including small numbers of studies, small study sizes and heterogeneity of results. However, the heterogeneity is difficult to estimate if only very few studies are included. Motivated by a systematic review in immunosuppression following liver transplantation in children, we investigate the properties of a range of commonly used frequentist and Bayesian procedures in simulation studies. Furthermore, the consequences for interval estimation of the common treatment effect in random-effects meta-analysis are assessed...
March 2017: Research Synthesis Methods
Ian Shrier, Tasha Beretvas
No abstract text is available yet for this article.
January 23, 2017: Research Synthesis Methods
Madeleine Ballard, Paul Montgomery
OBJECTIVE: To assess the conditions under which employing an overview of systematic reviews is likely to lead to a high risk of bias. STUDY DESIGN: To synthesise existing guidance concerning overview practice, a scoping review was conducted. Four electronic databases were searched with a pre-specified strategy (PROSPERO 2015:CRD42015027592) ending October 2015. Included studies needed to describe or develop overview methodology. Data were narratively synthesised to delineate areas highlighted as outstanding challenges or where methodological recommendations conflict...
January 10, 2017: Research Synthesis Methods
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