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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
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
Daisuke Yoneoka, Masayuki Henmi
Recently, the number of regression models has dramatically increased in several academic fields. However, within the context of meta-analysis, synthesis methods for such models have not been developed in a commensurate trend. One of the difficulties hindering the development is the disparity in sets of covariates among literature models. If the sets of covariates differ across models, interpretation of coefficients will differ, thereby making it difficult to synthesize them. Moreover, previous synthesis methods for regression models, such as multivariate meta-analysis, often have problems because covariance matrix of coefficients (i...
December 16, 2016: Research Synthesis Methods
Samson Henry Dogo, Allan Clark, Elena Kulinskaya
Temporal changes in magnitude of effect sizes reported in many areas of research are a threat to the credibility of the results and conclusions of meta-analysis. Numerous sequential methods for meta-analysis have been proposed to detect changes and monitor trends in effect sizes so that meta-analysis can be updated when necessary and interpreted based on the time it was conducted. The difficulties of sequential meta-analysis under the random-effects model are caused by dependencies in increments introduced by the estimation of the heterogeneity parameter τ(2) ...
December 8, 2016: Research Synthesis Methods
Alexander M Schoemann
Meta-analysis is a popular and flexible analysis that can be fit in many modeling frameworks. Two methods of fitting meta-analyses that are growing in popularity are structural equation modeling (SEM) and multilevel modeling (MLM). By using SEM or MLM to fit a meta-analysis researchers have access to powerful techniques associated with SEM and MLM. This paper details how to use one such technique, multiple group analysis, to test categorical moderators in meta-analysis. In a multiple group meta-analysis a model is fit to each level of the moderator simultaneously...
December 2016: Research Synthesis Methods
Amy Y Tsou, Jonathan R Treadwell
BACKGROUND: Systematic review (SR) abstracts are important for disseminating evidence syntheses to inform medical decision making. We assess reporting quality in SR abstracts using PRISMA for Abstracts (PRISMA-A), Cochrane Handbook, and Agency for Healthcare Research & Quality guidance. METHODS: We evaluated a random sample of 200 SR abstracts (from 2014) comparing interventions in the general medical literature. We assessed adherence to PRISMA-A criteria, problematic wording in conclusions, and whether "positive" studies described clinical significance...
December 2016: Research Synthesis Methods
Mai T Pham, Lisa Waddell, Andrijana Rajić, Jan M Sargeant, Andrew Papadopoulos, Scott A McEwen
BACKGROUND: The rapid review is an approach to synthesizing research evidence when a shorter timeframe is required. The implications of what is lost in terms of rigour, increased bias and accuracy when conducting a rapid review have not yet been elucidated. METHODS: We assessed the potential implications of methodological shortcuts on the outcomes of three completed systematic reviews addressing agri-food public health topics. For each review, shortcuts were applied individually to assess the impact on the number of relevant studies included and whether omitted studies affected the direction, magnitude or precision of summary estimates from meta-analyses...
December 2016: Research Synthesis Methods
David C Hoaglin
No abstract text is available yet for this article.
December 2016: Research Synthesis Methods
S M Goring, P Gustafson, Y Liu, S Saab, S K Cline, R W Platt
In a network meta-analysis, comparators of interest are ideally connected either directly or via one or more common comparators. However, in some therapeutic areas, the evidence base can produce networks that are disconnected, in which there is neither direct evidence nor an indirect route for comparing certain treatments within the network. Disconnected networks may occur when there is no accepted standard of care, when there has been a major paradigm shift in treatment, when use of a standard of care or placebo is debated, when a product receives orphan drug designation, or when there is a large number of available treatments and many accepted standards of care...
December 2016: Research Synthesis Methods
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