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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
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
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...
January 6, 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
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
Eiji Sadashima, Satoshi Hattori, Kunihiko Takahashi
In prognostic studies, a summary statistic such as a hazard ratio is often reported between low-expression and high-expression groups of a biomarker with a study-specific cutoff value. Recently, several meta-analyses of prognostic studies have been reported, but these studies simply combined hazard ratios provided by the individual studies, overlooking the fact that the cutoff values are study-specific. We propose a method to summarize hazard ratios with study-specific cutoff values by estimating the hazard ratio for a 1-unit change of the biomarker in the underlying individual-level model...
December 2016: Research Synthesis Methods
Joanne E McKenzie, G Peter Herbison, Jonathan J Deeks
When meta-analysing intervention effects calculated from continuous outcomes, meta-analysts often encounter few trials, with potentially a small number of participants, and a variety of trial analytical methods. It is important to know how these factors affect the performance of inverse-variance fixed and DerSimonian and Laird random effects meta-analytical methods. We examined this performance using a simulation study. Meta-analysing estimates of intervention effect from final values, change scores, ANCOVA or a random mix of the three yielded unbiased estimates of pooled intervention effect...
December 2016: Research Synthesis Methods
Kirsty M Rhodes, Rebecca M Turner, Julian P T Higgins
This paper investigates how inconsistency (as measured by the I(2) statistic) among studies in a meta-analysis may differ, according to the type of outcome data and effect measure. We used hierarchical models to analyse data from 3873 binary, 5132 continuous and 880 mixed outcome meta-analyses within the Cochrane Database of Systematic Reviews. Predictive distributions for inconsistency expected in future meta-analyses were obtained, which can inform priors for between-study variance. Inconsistency estimates were highest on average for binary outcome meta-analyses of risk differences and continuous outcome meta-analyses...
December 2016: Research Synthesis Methods
Christopher H Schmid
No abstract text is available yet for this article.
October 17, 2016: Research Synthesis Methods
Perke Jacobs, Wolfgang Viechtbauer
Meta-analyses are often used to synthesize the findings of studies examining the correlational relationship between two continuous variables. When only dichotomous measurements are available for one of the two variables, the biserial correlation coefficient can be used to estimate the product-moment correlation between the two underlying continuous variables. Unlike the point-biserial correlation coefficient, biserial correlation coefficients can therefore be integrated with product-moment correlation coefficients in the same meta-analysis...
September 15, 2016: Research Synthesis Methods
Meg Bennetts, Ed Whalen, Sima Ahadieh, Joseph C Cappelleri
Although well developed to assess efficacy questions, meta-analyses and, more generally, systematic reviews, have received less attention in application to safety-related questions. As a result, many open questions remain on how best to apply meta-analyses in the safety setting. This appraisal attempts to: (i) summarize the current guidelines for assessing individual studies, systematic reviews, and network meta-analyses; (ii) describe several publications on safety meta-analytic approaches; and (iii) present some of the questions and issues that arise with safety data...
September 9, 2016: Research Synthesis Methods
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