Measuring inconsistency in meta-analyses
Reads0
Chats0
TLDR
A new quantity is developed, I 2, which the authors believe gives a better measure of the consistency between trials in a meta-analysis, which is susceptible to the number of trials included in the meta- analysis.Abstract:
Cochrane Reviews have recently started including the quantity I 2 to help readers assess the consistency of the results of studies in meta-analyses. What does this new quantity mean, and why is assessment of heterogeneity so important to clinical practice?
Systematic reviews and meta-analyses can provide convincing and reliable evidence relevant to many aspects of medicine and health care.1 Their value is especially clear when the results of the studies they include show clinically important effects of similar magnitude. However, the conclusions are less clear when the included studies have differing results. In an attempt to establish whether studies are consistent, reports of meta-analyses commonly present a statistical test of heterogeneity. The test seeks to determine whether there are genuine differences underlying the results of the studies (heterogeneity), or whether the variation in findings is compatible with chance alone (homogeneity). However, the test is susceptible to the number of trials included in the meta-analysis. We have developed a new quantity, I 2, which we believe gives a better measure of the consistency between trials in a meta-analysis.
Assessment of the consistency of effects across studies is an essential part of meta-analysis. Unless we know how consistent the results of studies are, we cannot determine the generalisability of the findings of the meta-analysis. Indeed, several hierarchical systems for grading evidence state that the results of studies must be consistent or homogeneous to obtain the highest grading.2–4
Tests for heterogeneity are commonly used to decide on methods for combining studies and for concluding consistency or inconsistency of findings.5 6 But what does the test achieve in practice, and how should the resulting P values be interpreted?
A test for heterogeneity examines the null hypothesis that all studies are evaluating the same effect. The usual test statistic …read more
Citations
More filters
Journal ArticleDOI
Effect of anti-inflammatory treatment on depression, depressive symptoms, and adverse effects: a systematic review and meta-analysis of randomized clinical trials.
Ole Köhler,Michael E. Benros,Merete Nordentoft,Michael E. Farkouh,Rupa L Iyengar,Ole Mors,Jesper Krogh +6 more
TL;DR: The analysis suggests that anti-inflammatory treatment, in particular celecoxib, decreases depressive symptoms without increased risks of adverse effects, and supports a proof-of-concept concerning the use of anti- inflammatory treatment in depression.
Journal ArticleDOI
Interventions for preventing falls in older people in care facilities and hospitals
Ian D. Cameron,Lesley D Gillespie,M. Clare Robertson,Geoff R Murray,Keith D. Hill,Robert G. Cumming,Ngaire Kerse +6 more
TL;DR: Assessing the effectiveness of interventions designed to reduce falls by older people in care facilities and hospitals suggested that exercise might reduce falls in people in intermediate level facilities, and increase falls in facilities providing high levels of nursing care.
Journal ArticleDOI
The efficacy of probiotics in the treatment of irritable bowel syndrome: a systematic review
Paul Moayyedi,Alexander C. Ford,Nicholas J. Talley,Filippo Cremonini,Amy E. Foxx-Orenstein,Lawrence J. Brandt,Eamonn Martin Quigley +6 more
TL;DR: Probiotics appear to be efficacious in IBS, but the magnitude of benefit and the most effective species and strain are uncertain.
Journal ArticleDOI
Meta-analysis: surveillance with ultrasound for early-stage hepatocellular carcinoma in patients with cirrhosis.
Amit G. Singal,Michael L. Volk,Akbar K. Waljee,Ravi Salgia,Peter D.R. Higgins,Mary A.M. Rogers,Jorge A. Marrero +6 more
TL;DR: A majority of studies investigating the accuracy of ultrasound for detecting hepatocellular carcinoma (HCC) do not reflect how this test is used for surveillance vs. diagnosis.
Journal ArticleDOI
Depression and obesity: a meta-analysis of community-based studies.
Leonore de Wit,Floriana S. Luppino,Annemieke van Straten,Brenda W.J.H. Penninx,Frans G. Zitman,Pim Cuijpers +5 more
TL;DR: There is a significant positive association between depression and obesity in the general population, which appeared to be more marked among women, and subgroup analyses showed a trend indicating a possible significant difference between males and females.
References
More filters
Journal ArticleDOI
Quantifying heterogeneity in a meta‐analysis
TL;DR: It is concluded that H and I2, which can usually be calculated for published meta-analyses, are particularly useful summaries of the impact of heterogeneity, and one or both should be presented in publishedMeta-an analyses in preference to the test for heterogeneity.
Journal ArticleDOI
The combination of estimates from different experiments.
TL;DR: The problem of making a combined estimate has been discussed previously by Cochran and Yates and Cochran (1937) for agricultural experiments, and by Bliss (1952) for bioassays in different laboratories as discussed by the authors.
Journal ArticleDOI
Tamoxifen for early breast cancer: An overview of the randomised trials
TL;DR: The absolute improvement in recurrence was greater during the first 5 years, whereas the improvement in survival grew steadily larger throughout the first 10 years, and these benefits appeared to be largely irrespective of age, menopausal status, daily tamoxifen dose, and of whether chemotherapy had been given to both groups.
Journal Article
Tamoxifen for early breast cancer: an overview of the randomised trials. Early Breast Cancer Trialists' Collaborative Group
TL;DR: There have been many randomised trials of adjuvant tamoxifen among women with early breast cancer, and an updated overview of their results is presented in this paper, which approximately doubles the amount of evidence from trials of about 5 years of tamoxifier and, taking all trials together, on events occurring more than 5 years after randomisation.
Journal ArticleDOI
Funnel plots for detecting bias in meta-analysis: guidelines on choice of axis.
TL;DR: In this paper, the authors evaluated standard error, precision (inverse of standard error), variance, inverse of variance, sample size and log sample size (vertical axis) and log odds ratio, log risk ratio and risk difference (horizontal axis).