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Research Synthesis Methods

Miriam Luhnen, Barbara Prediger, Edmund A M Neugebauer, Tim Mathes
INTRODUCTION: The number of systematic reviews of health economic evaluations (SR-HEs) is increasing. We aimed at providing a detailed overview of the characteristics and applied methods in recently published SR-HEs. METHODS: We searched MEDLINE (03/2017) for SR-HEs published since 2015 using validated search filters. We included studies that performed a systematic review of full economic evaluations and searched at least one electronic database. We extracted data in a standardized, beforehand piloted form that was deduced from the items of the PRISMA and CHEERS checklists...
February 13, 2019: Research Synthesis Methods
G J Melendez-Torres, Katy Sutcliffe, Helen E D Burchett, Rebecca Rees, James Thomas
Qualitative comparative analysis (QCA) was originally developed as a tool for cross-national comparisons in macrosociology, but its use in evaluation and evidence synthesis of complex interventions is rapidly developing. QCA is theory-driven and relies on Boolean logic to identify pathways to an outcome (e.g. is the intervention effective or not?). We use the example of two linked systematic reviews on weight management programmes (WMPs) for adults-one focusing on user views (a 'views synthesis') and one focusing on the effectiveness of WMPs incorporating dietary and physical activity-to demonstrate how a synthesis of user views can supply a working theory to structure a QCA analysis...
February 8, 2019: Research Synthesis Methods
Lifeng Lin
Assessing publication bias is a critical procedure in meta-analyses for rating the synthesized overall evidence. Because statistical tests for publication bias are usually not powerful and only give P values that inform either the presence or absence of the bias, examining the asymmetry of funnel plots has been popular to investigate potentially missing studies and the direction of the bias. Most funnel plots present treatment effects against their standard errors, and the contours depicting studies' significance levels have been used in the plots to distinguish publication bias from other factors (such as heterogeneity and subgroup effects) that may cause the plots' asymmetry...
January 21, 2019: Research Synthesis Methods
Elizabeth Tipton, James E Pustejovsky, Hedyeh Ahmadi
Having surveyed the history and methods of meta-regression in a previous paper,1 in this paper we review which and how meta-regression methods are applied in recent research syntheses. To do so, we reviewed studies published in 2016 across four leading research synthesis journals: Psychological Bulletin, the Journal of Applied Psychology, Review of Education Research, and the Cochrane Library. We find that the best practices defined in the previous review are rarely carried out in practice. In light of the identified discrepancies, we consider how to move forward, first by identifying areas where further methods development is needed to address persistent problems in the field, and second by discussing how to more effectively disseminate points of methodological consensus...
January 7, 2019: Research Synthesis Methods
Robin Kosch, Klaus Jung
Research synthesis, e.g. by meta-analysis, is more and more considered in the area of high-dimensional data from molecular research such as gene and protein expression data, especially because most studies and experiments are performed with very small sample sizes. In contrast to most clinical and epidemiological trials, raw data is often available for high-dimensional expression data. Therefore, direct data merging followed by a joint analysis of selected studies can be an alternative to meta-analysis by p-value or effect size merging, or more generally spoken, the merging of results...
December 27, 2018: Research Synthesis Methods
Elizabeth Tipton, James E Pustejovsky, Hedyeh Ahmadi
At the beginning of the development of meta-analysis, understanding the role of moderators was given the highest priority, with meta-regression provided as a method for achieving this goal. Yet in current practice, meta-regression is not as commonly used as anticipated. This paper seeks to understand this mismatch by reviewing the history of meta-regression methods over the past 40 years. We divide this time span into four periods and examine three types of methodological developments within each period: technical, conceptual, and practical...
December 27, 2018: Research Synthesis Methods
Robbie C M van Aert, Marcel A L M van Assen, Wolfgang Viechtbauer
The effect sizes of studies included in a meta-analysis do often not share a common true effect size due to differences in for instance the design of the studies. Estimates of this so-called between-study variance are usually imprecise. Hence, reporting a confidence interval together with a point estimate of the amount of between-study variance facilitates interpretation of the meta-analytic results. Two methods that are recommended to be used for creating such a confidence interval are the Q-profile and generalized Q-statistic method that both make use of the Q-statistic...
December 27, 2018: Research Synthesis Methods
Allard J van Altena, Rene Spijker, Sílvia Delgado Olabarriaga
Systematic reviews are a cornerstone of today's evidence-informed decision making. With the rapid expansion of questions to be addressed and scientific information produced, there is a growing workload on reviewers, making the current practice unsustainable without the aid of automation tools. While many automation tools have been developed and are available, uptake seems to be lagging. For this reason, we set out to investigate the current level of uptake and what the potential barriers and facilitators are for the adoption of automation tools in systematic reviews...
December 18, 2018: Research Synthesis Methods
Katerina Papadimitropoulou, Theo Stijnen, Olaf M Dekkers, Saskia le Cessie
The vast majority of meta-analyses uses summary/aggregate data retrieved from published studies in contrast to meta-analysis of individual participant data (IPD). When the outcome is continuous and IPD are available, linear mixed modelling methods canbe employed in a one-stage approach. This allows for flexible modelling of within-study variability and between-study effects and accounts for the uncertainty in the estimates of between-study and within-study residual variances. However, IPD are seldom available...
December 6, 2018: Research Synthesis Methods
Xinru Li, Elise Dusseldorp, Jacqueline J Meulman
In meta-analytic studies, there are often multiple moderators available (e.g., study characteristics). In such cases, traditional meta-analysis methods often lack sufficient power to investigate interaction effects between moderators, especially high-order interactions. To overcome this problem, meta-CART was proposed: an approach that applies classification and regression trees (CART) to identify interactions, and then subgroup meta-analysis to test the significance of moderator effects. The aim of this study is to improve meta-CART upon two aspects: 1) to integrate the two steps of the approach into one; 2) to consistently take into account the fixed-effect or random-effects assumption in both the the interaction identification and testing process...
December 3, 2018: Research Synthesis Methods
Teegwendé V Porgo, Susan L Norris, Georgia Salanti, Leigh F Johnson, Julie A Simpson, Nicola Low, Matthias Egger, Christian L Althaus
Mathematical modelling studies are increasingly recognised as an important tool for evidence synthesis and to inform clinical and public health decision-making, particularly when data from systematic reviews of primary studies do not adequately answer a research question. However, systematic reviewers and guideline developers may struggle with using the results of modelling studies, due at least in part to the lack of a common understanding of concepts and terminology between evidence synthesis experts and mathematical modellers...
December 3, 2018: Research Synthesis Methods
James E Pustejovsky, Melissa Rodgers
Publication bias and other forms of outcome reporting bias are critical threats to the validity of findings from research syntheses. A variety of methods have been proposed for detecting selective outcome reporting in a collection of effect size estimates, including several methods based on assessment of asymmetry of funnel plots, such as Egger's regression test, the rank correlation test, and the Trim-and-Fill test. Previous research has demonstated that Egger's regression test is mis-calibrated when applied to log-odds ratio effect size estimates, due to artifactual correlation between the effect size estimate and its standard error...
December 2, 2018: Research Synthesis Methods
Carolyn Spry, Monika Mierzwinski-Urban
OBJECTIVE: The objective of this study was to investigate the impact of the peer review of literature search strategies prepared in support of rapid reviews. METHODS: A sample of 200 CADTH rapid reviews was selected. For each rapid review meeting the inclusion criteria, the pre-peer-reviewed and corresponding post-peer-reviewed search strategies were run, and the search results were compared. Bibliographic records retrieved solely by the post-peer-reviewed search strategy and included in the rapid review report were identified as representing "included studies...
December 2018: Research Synthesis Methods
Howard Thom, Ian R White, Nicky J Welton, Guobing Lu
Network meta-analysis compares multiple treatments from studies that form a connected network of evidence. However, for complex networks, it is not easy to see if the network is connected. We use simple techniques from graph theory to test the connectedness of evidence networks in network meta-analysis. The method is to build the adjacency matrix for a network, with rows and columns corresponding to the treatments in the network and entries being one or zero depending on whether the treatments have been compared or not, and with zeros along the diagonal...
November 7, 2018: Research Synthesis Methods
Sarah Donegan, Sofia Dias, Nicky J Welton
When numerous treatments exist for a disease (treatments 1, 2, 3 etc.), network meta-regression (NMR) examines whether each relative treatment effect (e.g. mean difference for 2 vs. 1, 3 vs. 1, 3 vs. 2 etc.) differs according to a covariate (e.g. disease severity). Two consistency assumptions underlie NMR: consistency of the treatment effects at the covariate value zero and consistency of the regression coefficients for the treatment by covariate interaction. The NMR results may be unreliable when the assumptions do not hold...
October 26, 2018: Research Synthesis Methods
Isabelle Albert, David Makowski
The mixed treatment comparison (MTC) method has been proposed to combine results across trials comparing several treatments. MTC allows coherent judgments on which of the treatments is the most effective. It produces estimates of the relative effects of each treatment compared with every other treatment by pooling direct and indirect evidence. In this article, we explore how this methodological framework can be used to rank a large number of agricultural crop species from yield data collected in field experiments...
October 24, 2018: Research Synthesis Methods
Jens Jap, Ian J Saldanha, Bryant T Smith, Joseph Lau, Christopher H Schmid, Tianjing Li
INTRODUCTION: During systematic reviews, data abstraction is labor- and time-intensive and error-prone. Existing data abstraction systems do not track specific locations and contexts of abstracted information. To address this limitation, we developed a software application, the Data Abstraction Assistant (DAA), and surveyed early users about their experience using DAA. FEATURES OF DAA: We designed DAA to encompass three essential features: (1) a platform for indicating the source of abstracted information; (2) compatibility with a variety of data abstraction systems; and (3) user-friendliness...
October 16, 2018: Research Synthesis Methods
Suzy Paisley, Margaret J Foster
No abstract text is available yet for this article.
October 16, 2018: Research Synthesis Methods
Andrew Booth
No abstract text is available yet for this article.
September 24, 2018: Research Synthesis Methods
Adam R Hafdahl
This ninth 'Article Alert' installment's print component presents 200 methodological articles about research synthesis published in 2014, all grouped by type of contribution and assigned descriptive keywords. More than 5300 articles, book chapters, and other types of work from 2004-2008 and 2014 have been added to the archive component since the eighth installment. The online Supporting Information provides this and all previous installments' print- and archive-component records, most with a DOI name or other online identifier...
September 9, 2018: Research Synthesis Methods
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