Swiss Medical Weekly, 2012

Meta-analyses overcome the limitation of small sample sizes or rare outcomes by pooling results from a number of individual studies to generate a single best estimate. As long as a meta-analysis is not limited by poor quality of included trials, unexplainable heterogeneity and/or reporting bias of individual trials, meta-analyses can be instrumental in reliably demonstrating benefit or harm of an intervention when results of individual randomised controlled trials are conflicting or inconclusive. Therefore meta-analyses should be conducted as part of a systematic review, i.e., a systematic approach to answer a focused clinical question. Important features of a systematic review are a comprehensive, reproducible search for primary studies, selection of studies using clear and transparent eligibility criteria, standardised critical appraisal of studies for quality, and investigation of heterogeneity among included studies. Cumulative meta-analysis may prevent delays in the introduction of effective treatments and may allow for early detection of harmful effects of interventions. As opposed to meta-analysis based on aggregate study data, individual patient data meta-analyses offer the advantage to use standardised criteria across trials and reliably investigate subgroup effects of interventions. Network meta-analysis allows the integration of data from direct and indirect comparisons in order to compare multiple treatments in a comprehensive analysis and determine the best treatment among several options. We conclude that meta-analysis has become a popular, versatile, and powerful tool. If rigorously conducted as part of a systematic review, it is essential for evidence-based decision making in clinical practice as well as on the health policy level.

International Journal of Clinical Practice, 2006

With the expanding volume of medical literature, meta-analysis, a form of systematic review, has become indispensable for clinicians for evidence-based decision making. While the number of meta-analyses has substantially increased during recent years, there are still controversial issues regarding their methodology, interpretation and clinical application. In this review, the basic concepts of meta-analysis have been discussed from a clinician's perspective in order to facilitate its understanding, appraising and applicability in clinical practice. Although randomised controlled trials are the usual source for meta-analysis, observational studies are also being increasingly considered for meta-analysis. Like every other research design, meta-analysis starts with formulating a question, followed by searching for related data, based on predefined criteria and strategies. Inclusion of studies must be carried out with careful consideration of their quality and assessment of homogeneity using graphical means as well as statistical tools such as Q statistics, I2 statistics and meta-regression. The pooled effect size is commonly calculated using either a ‘fixed effect model’ or ‘random effect model’. Publication bias and other source of bias should be investigated and the impact of potential confounders should be eliminated as required. Given the above-mentioned considerations, meta-analysis can provide a more precise estimate of an effect size to be used in clinical decision making.

Journal of Gene Medicine, 2021

With the explosive growth of medical information, it is almost impossible for healthcare providers to review and evaluate all relevant evidence to make the best clinical decisions. Meta‐analyses, which summarize all existing evidence and quantitatively synthesize individual studies, have become the best available evidence for informing clinical practice. This article introduces the common methods, steps, principles, strengths and limitations of meta‐analyses and aims to help healthcare providers and researchers obtain a basic understanding of meta‐analyses in clinical practice and research.

Journal of Anesthesiology and Reanimation Specialists’ Society, 2019

Meta-analysis is a frequently used statistical technique which uses to combine data from several studies to evaluate the effectiveness of treatment interventions. By combining results from independent studies, we can both increase power of the study (over individual studies) and improve estimates of the size of the effect. The processes of conducting meta-analysis include developing a protocol, selecting articles, developing inclusion criteria, collecting data, data analysis and interpreting results. A major limitation of the meta-analysis is that only relevant studies which have retrievable data can be included for analysis. This causes concern for publication bias. It is obvious that metaanalysis is a useful scientific method that can provide important information when summarizing medical literature. However, there can be misleading if the studies included are non-similar in their research question or collect different types of outcome data.

2020

The term meta-analysis was first used by G.V. Glass in 1976 in an article called "Primary, secondary and meta-analysis of investigations" ("Primaria, secundaria y meta-análisis de la investigación"). He used this term to refer to the statistical analysis of all the results obtained in different clinical studies regarding the same subject and that were to be analyzed together. At the beginning, this type of analysis was mainly used for the examination of social studies and psychology investigations, but later, during the 1980s, it became a popular method used in medicine; particularly in the cardiovascular, cancer and perinatal specialties. Nowadays it is not rare to find several medical articles using this method. For this study we decided to perform a meta-analysis and also combine the results of the studies because when the sample size increases, the statistical potential increases as well. Furthermore, when including studies and researches performed in different Health Centers, the results obtained can be easily generalized. Nevertheless, the meta-analysis method has its controversies, many of them due to an excessive use of the method together with a lack of methodological rigor; there are many limitations to be considered when evaluating the results of a meta-analysis. In this article we will focus mainly on the statistical aspects of the subject, from the point of view of the description of the methods, indications and interpretations, without specifying other details such as the protocols for carrying out a systematic review or statistical formulas. The focus will be on the analytical methods used in meta-analyses of controlled clinical trials evaluating therapeutic efficacy or adverse reactions.

The Journal of Clinical Hypertension, 2014

The practice of evidence-based medicine requires physicians to be familiar with the most relevant research published in the medical literature. 1 Individual randomized clinical trials are well suited to provide compelling evidence of an intervention's therapeutic benefit. However, it has become very difficult (arguably impossible) for physicians to read every publication of relevance to their particular specialty. Systematic reviews and meta-analyses have therefore become increasingly important. Systematic reviews are descriptive in nature, and "collate, compare, discuss, and summarize the current results" in a particular field. 4 Meta-analysis goes a step further, providing us with a statistical technique to combine results from multiple individual trials and then use this dataset to conduct a new analysis that we could not conduct on the basis of any of the individual trial's datasets.

BMC Medical Research Methodology, 2011

Background Cochrane systematic reviews collate and summarise studies of the effects of healthcare interventions. The characteristics of these reviews and the meta-analyses and individual studies they contain provide insights into the nature of healthcare research and important context for the development of relevant statistical and other methods. Methods We classified every meta-analysis with at least two studies in every review in the January 2008 issue of the Cochrane Database of Systematic Reviews (CDSR) according to the medical specialty, the types of interventions being compared and the type of outcome. We provide descriptive statistics for numbers of meta-analyses, numbers of component studies and sample sizes of component studies, broken down by these categories. Results We included 2321 reviews containing 22,453 meta-analyses, which themselves consist of data from 112,600 individual studies (which may appear in more than one meta-analysis). Meta-analyses in the areas of gyna...

Journal of nephrology

Meta-analyses are frequently criticized because in most cases they are compiled from quite heterogeneous studies. In spite of this limitation meta-analyses are increasingly published because in many areas of clinical research the results of individual studies are devoid of statistical power and end up with conflicting results. Metaanalyses, if performed with a rigorous and exhaustive search of all accountable information on a specific topic, have the potential of overcoming the drawbacks of single studies and, in addition, of adjusting for publication bias and interstudy variability. These strengths of metaanalyses can be exploited to provide conclusive answers on diagnostic and therapeutic issues being debated, which in turn may help guide doctors toward more rational decisions.

British Journal of Surgery, 2000

S u m m a r y B a c k g r o u n d The Quality of Reporting of Meta-analyses (QUOROM) conference was convened to address standards for improving the quality of reporting of meta-analyses of clinical randomised controlled trials (RCTs).

Nature Clinical Practice Rheumatology, 2008

RevIew CRITeRIa No formal search of the literature was performed. Information was obtained from previous systematic reviews conducted by the authors, and from published reviews, textbooks and articles discussing the methodology of systematic reviews and meta-analyses.