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Research Synthesis Methods

Yuan Zhang, Elie A Akl, Holger J Schünemann
Systematic reviews are essential to produce trustworthy guidelines. To assess the certainty of a body of evidence included in a systematic review the Grading of Recommendations Assessment, Development and Evaluation (GRADE) working group has developed an approach that is currently used by over 100 organisations, including the World Health Organization and the Cochrane Collaboration. GRADE provides operational definitions and instructions to rate the certainty of the evidence for each outcome in a review as high, moderate, low, or very low for the effects of interventions, prognostic estimates, values and preferences, test accuracy and resource utilization...
July 14, 2018: Research Synthesis Methods
María Rubio-Aparicio, José Antonio López-López, Julio Sánchez-Meca, Fulgencio Marín-Martínez, Wolfgang Viechtbauer, Wim Van den Noortgate
The random-effects model, applied in most meta-analyses nowadays, typically assumes normality of the distribution of the effect parameters. The purpose of this study was to examine the performance of various random-effects methods (standard method, Hartung´s method, profile likelihood method and bootstrapping) for computing an average effect size estimate and a confidence interval (CI) around it, when the normality assumption is not met. For comparison purposes, we also included the fixed-effect model. We manipulated a wide range of conditions, including conditions with some degree of departure from the normality assumption, using Monte Carlo simulation...
July 10, 2018: Research Synthesis Methods
José A López-López, Matthew J Page, Mark W Lipsey, Julian P T Higgins
Systematic reviews often encounter primary studies that report multiple effect sizes based on data from the same participants. These have the potential to introduce statistical dependency into the meta-analytic data set. In this paper we provide a tutorial on dealing with effect size multiplicity within studies in the context of meta-analyses of intervention and association studies, recommending a three-step approach. The first step is to define the research question and consider the extent to which it mainly reflects interest in mean effect sizes (which we term a 'convergent' approach) or an interest in exploring heterogeneity (which we term a 'divergent' approach)...
July 3, 2018: Research Synthesis Methods
Piotr Przybyła, Austin J Brockmeier, Georgios Kontonatsios, Marie-Annick Le Pogam, John McNaught, Erik von Elm, Kay Nolan, Sophia Ananiadou
Screening references is a time-consuming step necessary for systematic reviews and guideline development. Previous studies have shown that human effort can be reduced by using machine-learning software to prioritise large reference collections such that the majority of relevant references are identified before screening is completed. We describe and evaluate RobotAnalyst, a web-based software system that combines text-mining and machine-learning algorithms for organising references by their content and actively prioritising them based on a relevancy classification model trained and updated throughout the process...
June 28, 2018: Research Synthesis Methods
Joy Leahy, Aisling O'Leary, Nezam Afdhal, Emma Gray, Scott Milligan, Malte H Wehmeyer, Cathal Walsh
The use of Individual Patient Data (IPD) in Network Meta Analysis (NMA) is becoming increasingly popular. However, as most studies do not report IPD, most NMAs are carried out using aggregate data (AD) for at least some, if not all, of the studies. We investigate the benefits of including varying proportions of IPD studies in an NMA. Several models have previously been developed for including both AD and IPD in the same NMA. We carried out a simulation study based on these models to examine the impact of additional IPD studies on the accuracy and precision of the estimates of both the treatment effect and the covariate effect...
June 20, 2018: Research Synthesis Methods
Evangelos Kontopantelis
BACKGROUND: Individual patient data (IPD) meta-analysis allows for the exploration of heterogeneity and can identify subgroups that most benefit from an intervention (or exposure), much more successfully than meta-analysis of aggregate data. One-stage or two-stage IPD meta-analysis is possible, with the former using mixed-effects regression models and the latter obtaining study estimates through simpler regression models before aggregating using standard meta-analysis methodology. However, a comprehensive comparison of the two methods, in practice, is lacking...
May 22, 2018: Research Synthesis Methods
Yu-Xuan Su, Yu-Kang Tu
Network meta-analysis compares multiple treatments in terms of their efficacy and harm by including evidence from randomized controlled trials. Most clinical trials use parallel design, where patients are randomly allocated to different treatments and receive only one treatment. However, some trials use within person designs such as split-body, split-mouth and cross-over designs, where each patient may receive more than one treatment. Data from treatment arms within these trials are no longer independent, so the correlations between dependent arms need to be accounted for within the statistical analyses...
May 22, 2018: Research Synthesis Methods
Juan Víctor Ariel Franco, Virginia Laura Garrote, Camila Micaela Escobar Liquitay, Valeria Vietto
OBJECTIVE: Search strategies are essential for the adequate retrieval of studies in a systematic review (SR). Our objective was to identify problems in the design and reporting of search strategies in a sample of new Cochrane SRs first published in The Cochrane Library in 2015. STUDY DESIGN AND SETTING: We took a random sample of 70 new Cochrane SRs of interventions published in 2015. We evaluated their design and reporting of search strategies using the recommendations from the Cochrane Handbook for Systematic Reviews of Interventions, the Methodological Expectations of Cochrane Intervention Reviews, and the Peer Review of Electronic Search Strategies evidence-based guideline...
May 15, 2018: Research Synthesis Methods
S C Freeman, D Fisher, J F Tierney, J R Carpenter
BACKGROUND: Stratified medicine seeks to identify patients most likely to respond to treatment. Individual participant data (IPD) network meta-analysis (NMA) models have greater power than individual trials to identify treatment-covariate interactions (TCIs). Treatment-covariate interactions contain "within" and "across" trial interactions, where the across-trial interaction is more susceptible to confounding and ecological bias. METHODS: We considered a network of IPD from 37 trials (5922 patients) for cervical cancer (2394 events), where previous research identified disease stage as a potential interaction covariate...
May 8, 2018: Research Synthesis Methods
Claire Watkins, Iain Bennett
In studies with time-to-event data, outcomes may be reported as hazard ratios (HR) or binomial counts/proportions at a specific time point. If the intent is to synthesise evidence by performing a meta-analysis or network meta-analysis (NMA) using the HR as the measure of treatment effect, studies that only report binomial data cannot be included in the network. Methods for converting binomial data to HRs were investigated, so that studies reporting binomial data only could be included in a network of HR data...
April 29, 2018: Research Synthesis Methods
Adam R Hafdahl
This eighth installment of 'Article Alerts' includes a print component with 200 methodological articles about research synthesis published in 2013. Since the preceding installment, more than 3400 articles, dissertations, book chapters, and other types of work in this methodological domain have been added to the archive component, all from 2009 to 2013. The online Supporting Information now includes over half of the parent compilation's more than 26 000 records: 1000 from the print component and more than 13 000 from the archive component...
June 2018: Research Synthesis Methods
Nazila Alinaghi, W Robert Reed
This paper studies the performance of the FAT-PET-PEESE (FPP) procedure, a commonly employed approach for addressing publication bias in the economics and business meta-analysis literature. The FPP procedure is generally used for 3 purposes: (1) to test whether a sample of estimates suffers from publication bias, (2) to test whether the estimates indicate that the effect of interest is statistically different from zero, and (3) to obtain an estimate of the mean true effect. Our findings indicate that the FPP procedure performs well in the basic but unrealistic environment of fixed effects, where all estimates are assumed to derive from a single population value and sampling error is the only reason for why studies produce different estimates...
June 2018: Research Synthesis Methods
O O Babatunde, V Tan, J L Jordan, K Dziedzic, C A Chew-Graham, C Jinks, J Protheroe, D A van der Windt
BACKGROUND & AIMS: Barriers to dissemination and engagement with evidence pose a threat to implementing evidence-based medicine. Understanding, retention, and recall can be enhanced by visual presentation of information. The aim of this exploratory research was to develop and evaluate the accessibility and acceptability of visual summaries for presenting evidence syntheses with multiple exposures or outcomes to professional and lay audiences. METHODS: "Evidence flowers" were developed as a visual method of presenting data from 4 case scenarios: 2 complex evidence syntheses with multiple outcomes, Cochrane reviews, and clinical guidelines...
June 2018: Research Synthesis Methods
Lifeng Lin, Haitao Chu
In medical sciences, a disease condition is typically associated with multiple risk and protective factors. Although many studies report results of multiple factors, nearly all meta-analyses separately synthesize the association between each factor and the disease condition of interest. The collected studies usually report different subsets of factors, and the results from separate analyses on multiple factors may not be comparable because each analysis may use different subpopulation. This may impact on selecting most important factors to design a multifactor intervention program...
June 2018: Research Synthesis Methods
Sarah Donegan, Sofia Dias, Catrin Tudur-Smith, Valeria Marinho, Nicky J Welton
BACKGROUND: Meta-regression results must be interpreted taking into account the range of covariate values of the contributing studies. Results based on interpolation or extrapolation may be unreliable. In network meta-regression (NMR) models, which include covariates in network meta-analyses, results are estimated using direct and indirect evidence; therefore, it may be unclear which studies and covariate values contribute to which result. We propose graphs to help understand which trials and covariate values contribute to each NMR result and to highlight extrapolation or interpolation...
June 2018: Research Synthesis Methods
Ani Movsisyan, Jane Dennis, Eva Rehfuess, Sean Grant, Paul Montgomery
INTRODUCTION: Rating the quality of a body of evidence is an increasingly common component of research syntheses on intervention effectiveness. This study sought to identify and examine existing systems for rating the quality of a body of evidence on the effectiveness of health and social interventions. METHODS: We used a multicomponent search strategy to search for full-length reports of systems for rating the quality of a body of evidence on the effectiveness of health and social interventions published in English from 1995 onward...
June 2018: Research Synthesis Methods
Xin Victoria Wang, Bernard Cole, Marco Bonetti, Richard D Gelber
We recently developed a method called Meta-STEPP based on the fixed-effects meta-analytic approach to explore treatment effect heterogeneity across a continuous covariate for individual time-to-event data arising from multiple clinical trials. Meta-STEPP forms overlapping subpopulation windows (meta-windows) along a continuous covariate of interest, estimates the overall treatment effect in each meta-window using standard fixed-effects method, plots them against the continuous covariate, and tests for treatment-effect heterogeneity across the range of covariate values...
June 2018: Research Synthesis Methods
Chris Cooper, Rebecca Lovell, Kerryn Husk, Andrew Booth, Ruth Garside
BACKGROUND: We undertook a systematic review to evaluate the health benefits of environmental enhancement and conservation activities. We were concerned that a conventional process of study identification, focusing on exhaustive searches of bibliographic databases as the primary search method, would be ineffective, offering limited value. The focus of this study is comparing study identification methods. We compare (1) an approach led by searches of bibliographic databases with (2) an approach led by supplementary search methods...
June 2018: Research Synthesis Methods
Burak Kürsad Günhan, Tim Friede, Leonhard Held
Network meta-analysis (NMA) is gaining popularity for comparing multiple treatments in a single analysis. Generalized linear mixed models provide a unifying framework for NMA, allow us to analyze datasets with dichotomous, continuous or count endpoints, and take into account multiarm trials, potential heterogeneity between trials and network inconsistency. To perform inference within such NMA models, the use of Bayesian methods is often advocated. The standard inference tool is Markov chain Monte Carlo (MCMC), which is computationally expensive and requires convergence diagnostics...
June 2018: Research Synthesis Methods
Danielle L Burke, Joie Ensor, Kym I E Snell, Danielle van der Windt, Richard D Riley
Percentage study weights in meta-analysis reveal the contribution of each study toward the overall summary results and are especially important when some studies are considered outliers or at high risk of bias. In meta-analyses of test accuracy reviews, such as a bivariate meta-analysis of sensitivity and specificity, the percentage study weights are not currently derived. Rather, the focus is on representing the precision of study estimates on receiver operating characteristic plots by scaling the points relative to the study sample size or to their standard error...
June 2018: Research Synthesis Methods
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