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Research Synthesis Methods

Hannah Wood, Annette O'Connor, Jan Sargeant, Julie Glanville
INTRODUCTION: Systematic review methods are now being used for reviews of food production, food safety and security, plant health, and animal health and welfare. Information retrieval methods in this context have been informed by human healthcare approaches and ideally should be based on relevant research and experience. OBJECTIVE: This narrative review seeks to identify and summarise current research-based evidence and experience on information retrieval for systematic reviews in food and feed topics...
January 9, 2018: Research Synthesis Methods
Iain Marshall, Anna Noel Storr, Joël Kuiper, James Thomas, Byron C Wallace
Machine learning (ML) algorithms have proven highly accurate for identifying Randomized Controlled Trials (RCTs), but are not used much in practice, in part because the best way to make use of the technology in a typical workflow is unclear. In this work we evaluate ML models for RCT classification (Support Vector Machines [SVMs], Convolutional Neural Networks [CNNs], and ensemble approaches). We trained and optimised SVM and CNN models on the titles and abstracts of the Cochrane Crowd RCT set. We evaluated the models on an external dataset (Clinical Hedges), allowing direct comparison with traditional database search filters...
January 4, 2018: Research Synthesis Methods
Xin Victoria Wang, Bernard Cole, Marco Bonetti, Richard D Gelbera
We recently developed a method called Meta-STEPP [1] 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...
December 27, 2017: 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: (i) an approach led by searches of bibliographic databases to (ii) an approach led by supplementary search methods...
November 29, 2017: 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 (GLMMs) provide a unifying framework for NMA, allow us to analyze datasets with dichotomous, continuous or count endpoints, and take into account multi-arm 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 chainMonte Carlo (MCMC), which is computationally expensive and requires convergence diagnostics...
November 29, 2017: 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 ROC plots by scaling the points relative to the study sample size or to their standard error...
November 7, 2017: Research Synthesis Methods
J Burns, S Polus, L Brereton, J Chilcott, S E Ward, L M Pfadenhauer, E A Rehfuess
We describe a combination of methods for assessing the effectiveness of complex interventions, especially where substantial heterogeneity with regard to the population, intervention, comparison, outcomes and study design of interest is expected. We applied these methods in a recent systematic review of the effectiveness of reinforced home-based palliative care (rHBPC) interventions, which included home-based care with an additional and explicit component of lay caregiver support. We first summarized the identified evidence, deemed inappropriate for statistical pooling, graphically by creating harvest plots...
November 4, 2017: Research Synthesis Methods
Aogán Delaney, Peter A Tamás
Despite recognition that database search alone is inadequate even within the health sciences, it appears that reviewers in fields that have adopted systematic review are choosing to rely primarily, or only, on database search for information retrieval. This commentary reminds readers of factors that call into question the appropriateness of default reliance on database searches particularly as systematic review is adapted for use in new and lower consensus fields. It then discusses alternative methods for information retrieval that require development, formalisation, and evaluation...
November 4, 2017: Research Synthesis Methods
Anthea Sutton, Maria Carmen Galvan De La Cruz, Joanna Leaviss, Andrew Booth
INTRODUCTION: Registration and publication of trial protocols has become increasingly important and a requirement in some sources of funding and publication. Increased access to protocols yields many potential benefits, but there are issues regarding identification of published protocols. The aim of this investigation is to compare methods of retrieval for identifying trial protocols in a systematic review. METHODS: Six stages of searching (checking published trial reports, searching journal websites, Internet searching, trial registers, bibliographic databases, contact with authors) were completed to identify 74 trial protocols...
October 31, 2017: Research Synthesis Methods
Morwenna Rogers, Alison Bethel, Rebecca Abbott
BACKGROUND: Qualitative research in dementia improves understanding of the experience of people affected by dementia. Searching databases for qualitative studies is problematic. Qualitative specific search strategies might help with locating studies. OBJECTIVE: To examine the effectiveness of five strategies across four major databases for retrieving qualitative studies in dementia. examine the effectiveness (sensitivity and precision) of five qualitative strategies on locating qualitative research studies in dementia in four major databases (MEDLINE, EMBASE, PsycINFO and CINAHL) METHODS: Qualitative dementia studies were checked for inclusion on MEDLINE, EMBASE, PsycINFO and CINAHL...
October 28, 2017: Research Synthesis Methods
Wichor M Bramer, Melissa L Rethlefsen, Frans Mast, Jos Kleijnen
OBJECTIVE: To evaluate and validate the time of completion and results of a new method of searching for systematic reviews, the exhaustive search method (ESM), using a pragmatic comparison. METHODS: Single-line search strategies were prepared in a text document. Term completeness was ensured with a novel optimization technique. Macros in MS Word converted the syntaxes between databases and interfaces almost automatically. We compared search characteristics, such as number of search terms and databases, and outcomes, such as number of included and retrieved references and precision, from ESM searches and other Dutch academic hospitals identified by searching PubMed for systematic reviews published between 2014 and 2016...
October 26, 2017: Research Synthesis Methods
John W Stevens, Christine Fletcher, Gerald Downey, Anthea Sutton
A network meta-analysis allows a simultaneous comparison between treatments evaluated in RCTs that share at least one treatment with at least one other study. Estimates of treatment effects may be required for treatments across disconnected networks of evidence, which requires a different statistical approach and modelling assumptions to account for imbalances in prognostic variable and treatment effect modifiers between studies. In this paper, we review and discuss methods for comparing treatments evaluated in studies which form disconnected networks of evidence...
October 26, 2017: Research Synthesis Methods
Simon Briscoe
The literature searches which are used to identify studies for inclusion in a systematic review should be comprehensively reported. This ensures that the literature searches are transparent and reproducible, which is important for assessing the strengths and weaknesses of a systematic review and re-running the literature searches when conducting an update review. Web searching using search engines and the websites of topically relevant organisations is sometimes used as a supplementary literature search method...
October 24, 2017: Research Synthesis Methods
Evan Mayo-Wilson, Tianjing Li, Nicole Fusco, Kay Dickersin
Data for individual trials included in systematic reviews may be available in multiple sources. For example, a single trial might be reported in two journal articles and three conference abstracts. Because of differences across sources, source selection can influence the results of systematic reviews. We used our experience in the Multiple Data Sources in Systematic Reviews (MUDS) study, and evidence from previous studies, to develop practical guidance for using multiple data sources in systematic reviews. We recommend: (1) Specify which sources you will use...
October 23, 2017: Research Synthesis Methods
Chuan Hong, Richard D Riley, Yong Chen
Multivariate meta-analysis, which jointly analyzes multiple and possibly correlated outcomes in a single analysis, is becoming increasingly popular in recent years. An attractive feature of the multivariate meta-analysis is its ability to account for the dependence between multiple estimates from the same study. However, standard inference procedures for multivariate meta-analysis require the knowledge of within-study correlations, which are usually unavailable. This limits standard inference approaches in practice...
October 21, 2017: Research Synthesis Methods
Annika Hoyer, Stefan Hirt, Oliver Kuss
Systematic reviews and meta-analyses are the cornerstones of evidence based medicine and inform treatment, diagnosis, or prevention of individual patients as well as policy decisions in health care. Statistical methods for the meta-analysis of intervention studies are well established today. Meta-analysis for diagnostic accuracy trials has also been a vivid research area in recent years which is especially due to the increased complexity of their bivariate outcome of sensitivity and specificity. The situation is even more challenging when single studies report a full ROC curve with several pairs of sensitivity and specificity, each pair for a different threshold...
October 20, 2017: Research Synthesis Methods
J Ensor, J J Deeks, E C Martin, R D Riley
INTRODUCTION: For tests reporting continuous results, primary studies usually provide test performance at multiple but often different thresholds. This creates missing data when performing a meta-analysis at each threshold. A standard meta-analysis (NI: No Imputation) ignores such missing data. A Single Imputation (SI) approach was recently proposed to recover missing threshold results. Here, we propose a new method (MIDC) that performs Multiple Imputation of the missing threshold results using Discrete Combinations...
October 19, 2017: Research Synthesis Methods
Annette Schultz, Leah Goertzen, Janet Rothney, Pamela Wener, Jennifer Enns, Gayle Halas, Alan Katz
Knowledge translation is a central focus of the health research community, which includes strategies to synthesize published research to support uptake within health care practice and policy arenas. Within the literature concerning review methodologies, a new discussion has emerged concerning methods that review and synthesize published review articles. In this paper, our multidisciplinary team from family medicine, nursing, dental hygiene, kinesiology, occupational therapy, physiology, population health, clinical psychology, and library sciences contributes to this discussion by sharing our experiences in conducting 3 scoping reviews of published review studies...
October 15, 2017: Research Synthesis Methods
George Karabatsos
There is growing concern that much of the published research literature is distorted by the pursuit of statistically significant results. In a seminal article, Ioannidis and Trikalinos (2007, Clinical Trials) proposed an omnibus (I&T) test for significance chasing (SC) biases. This test compares the observed number of studies that report statistically-significant results, against their expected number based on study power, assuming a common effect size across studies. The current article extends this approach by developing a Bayesian nonparametric (BNP) meta-regression model and test of SC bias, which can diagnose bias at the individual study level...
October 6, 2017: Research Synthesis Methods
Gerta Rücker, Guido Schwarzer
Network meta-analysis has evolved into a core method for evidence synthesis in health care. In network meta-analysis, three or more treatments for a given medical condition are compared, based on a number of clinical studies, usually randomized controlled trials. Often many different endpoints are investigated, related to different aspects of the patient's outcome, such as efficacy, safety, acceptability or costs of a treatment. Different outcomes may lead to different rankings of the treatments. We use the existing theory of partially ordered sets and show how the relations between the treatments in a network meta-analysis can be illustrated by Hasse diagrams, that is, directed graphs showing the partial order relations, and by structured scatter plots and biplots...
October 5, 2017: Research Synthesis Methods
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