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Peter C Gøtzsche

Bio: Peter C Gøtzsche is an academic researcher from Cochrane Collaboration. The author has contributed to research in topics: Systematic review & Placebo. The author has an hindex of 90, co-authored 413 publications receiving 147009 citations. Previous affiliations of Peter C Gøtzsche include University of Copenhagen & Copenhagen University Hospital.


Papers
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Journal ArticleDOI
13 Oct 2001-BMJ
TL;DR: Too often, reviewers' conclusions over-rated the benefits of new interventions and readers of Cochrane reviews should remain cautious, especially regarding conclusions that favour new interventions.
Abstract: Objective: To assess the quality of Cochrane reviews. Design: Ten methodologists affiliated with the Cochrane Collaboration independently examined, in a semistructured way, the quality of reviews first published in 1998. Each review was assessed by two people; if one of them noted any major problems, they agreed on a common assessment. Predominant types of problem were categorised. Setting: Cyberspace collaboration coordinated from the Nordic Cochrane Centre. Studies: All 53 reviews first published in issue 4 of the Cochrane Library in 1998. Main outcome measure: Proportion of reviews with various types of major problem. Results: No problems or only minor ones were found in most reviews. Major problems were identified in 15 reviews (29%). The evidence did not fully support the conclusion in nine reviews (17%), the conduct or reporting was unsatisfactory in 12 reviews (23%), and stylistic problems were identified in 12 reviews (23%). The problematic conclusions all gave too favourable a picture of the experimental intervention. Conclusions: Cochrane reviews have previously been shown to be of higher quality and less biased on average than other systematic reviews, but improvement is always possible. The Cochrane Collaboration has taken steps to improve editorial processes and the quality of its reviews. Meanwhile, the Cochrane Library remains a key source of evidence about the effects of healthcare interventions. Its users should interpret reviews cautiously, particularly those with conclusions favouring experimental interventions and those with many typographical errors. What is already known on this topic Cochrane reviews are, on average, more systematic and less biased than systematic reviews published in paper journals Errors and biases also occur in Cochrane reviews What this study adds Too often, reviewers9 conclusions over-rated the benefits of new interventions Readers of Cochrane reviews should remain cautious, especially regarding conclusions that favour new interventions The Cochrane Collaboration has taken steps to improve the quality of reviews

157 citations

Journal ArticleDOI
TL;DR: The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) as mentioned in this paper, a group of researchers, metodologos, investigadores, and editores de revistas, formularon recomendaciones sobre lo que deberia contener una notificacion precisa of un estudio observacional.
Abstract: A pesar de que la mayor parte de la investigacion biomedica es de tipo observacional, la informacion difundida sobre estas investigaciones es a menudo insuficiente, lo que dificulta la evaluacion de sus puntos fuertes y debiles para la generalizacion de sus conclusiones. En el marco de la iniciativa STROBE (Strengthening the Reporting of Observational Studies in Epidemiology), se formularon las recomendaciones sobre lo que deberia contener una notificacion precisa de un estudio observacional. Decidimos limitar el alcance de las recomendaciones a tres grandes modalidades de estudio: de cohortes, de casos y controles, y transversales. En septiembre de 2004 organizamos un taller de 2 dias con metodologos, investigadores y editores de revistas para elaborar una lista de verificacion de distintos puntos. Esta lista fue revisada posteriormente en varias reuniones del grupo de coordinacion y en discusiones mantenidas por correo electronico con los principales participantes en STROBE, teniendo en cuenta la evidencia empirica y diversas consideraciones metodologicas. El taller y el posterior proceso iterativo de consulta y revision desembocaron en una lista de verificacion de 22 puntos (la declaracion STROBE) que guardan relacion con el titulo, el resumen, la introduccion y las secciones de metodos, resultados y discusion de los articulos. Dieciocho puntos son comunes a los tres tipos de estudio, y cuatro son especificas para cada uno de ellos. Se ha publicado separadamente un documento de explicacion y elaboracion al que puede accederse libremente en los sitios web de PLoS Medicine, Annals of Internal Medicine y Epidemiology. Esperamos que la declaracion STROBE contribuya a mejorar la calidad de la publicacion de los estudios observacionales.

156 citations

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153 citations

Journal ArticleDOI
28 Jan 2009-BMJ
TL;DR: Peter Gøtzsche and colleagues argue that women are still not given enough, nor correct, information about the harms of screening for breast cancer.
Abstract: Peter Gotzsche and colleagues argue that women are still not given enough, nor correct, information about the harms of screening

152 citations

Journal ArticleDOI
09 Sep 2000-BMJ
TL;DR: When a meta-analysis showed that the use of human albumin increased mortality1 this result applied to all three groups of critically ill patients studied, it would be wrong to interpret this result as meaning that clinicians should continue to give these patients albumin.
Abstract: In the world of clinical trials and meta-analyses there is an important debate between the “lumpers” and the “splitters.” This relates to whether the overall findings of clinical trials and meta-analyses are the appropriate outcome to apply to individuals (lumping) or whether it is better to try to match the characteristics of particular patients to characteristics of subgroups within trials or meta-analyses (splitting). Although the splitters' view seems intuitively correct, there are usually substantial clinical and methodological advantages to lumping. The generalisability and usefulness of meta-analyses are increased considerably if the individual trials cover different patient populations, settings, and concomitant routine care. For example, when a meta-analysis showed that the use of human albumin increased mortality1 this result applied to all three groups of critically ill patients studied. For patients with hypovolaemia the difference was not conventionally significant (95% confidence interval for the odds ratio 0.99 to 3.15), but it would be wrong to interpret this result as meaning that clinicians should continue to give these patients albumin. Most significant results will disappear because of lack of power if trials in a meta-analysis are split up into a large enough number of subgroups. It is more relevant that the point estimates were similar …

149 citations


Cited by
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Journal ArticleDOI
TL;DR: Moher et al. as mentioned in this paper introduce PRISMA, an update of the QUOROM guidelines for reporting systematic reviews and meta-analyses, which is used in this paper.
Abstract: David Moher and colleagues introduce PRISMA, an update of the QUOROM guidelines for reporting systematic reviews and meta-analyses

62,157 citations

Journal Article
TL;DR: The QUOROM Statement (QUality Of Reporting Of Meta-analyses) as mentioned in this paper was developed to address the suboptimal reporting of systematic reviews and meta-analysis of randomized controlled trials.
Abstract: Systematic reviews and meta-analyses have become increasingly important in health care. Clinicians read them to keep up to date with their field,1,2 and they are often used as a starting point for developing clinical practice guidelines. Granting agencies may require a systematic review to ensure there is justification for further research,3 and some health care journals are moving in this direction.4 As with all research, the value of a systematic review depends on what was done, what was found, and the clarity of reporting. As with other publications, the reporting quality of systematic reviews varies, limiting readers' ability to assess the strengths and weaknesses of those reviews. Several early studies evaluated the quality of review reports. In 1987, Mulrow examined 50 review articles published in 4 leading medical journals in 1985 and 1986 and found that none met all 8 explicit scientific criteria, such as a quality assessment of included studies.5 In 1987, Sacks and colleagues6 evaluated the adequacy of reporting of 83 meta-analyses on 23 characteristics in 6 domains. Reporting was generally poor; between 1 and 14 characteristics were adequately reported (mean = 7.7; standard deviation = 2.7). A 1996 update of this study found little improvement.7 In 1996, to address the suboptimal reporting of meta-analyses, an international group developed a guidance called the QUOROM Statement (QUality Of Reporting Of Meta-analyses), which focused on the reporting of meta-analyses of randomized controlled trials.8 In this article, we summarize a revision of these guidelines, renamed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses), which have been updated to address several conceptual and practical advances in the science of systematic reviews (Box 1). Box 1 Conceptual issues in the evolution from QUOROM to PRISMA

46,935 citations

Journal ArticleDOI
13 Sep 1997-BMJ
TL;DR: Funnel plots, plots of the trials' effect estimates against sample size, are skewed and asymmetrical in the presence of publication bias and other biases Funnel plot asymmetry, measured by regression analysis, predicts discordance of results when meta-analyses are compared with single large trials.
Abstract: Objective: Funnel plots (plots of effect estimates against sample size) may be useful to detect bias in meta-analyses that were later contradicted by large trials. We examined whether a simple test of asymmetry of funnel plots predicts discordance of results when meta-analyses are compared to large trials, and we assessed the prevalence of bias in published meta-analyses. Design: Medline search to identify pairs consisting of a meta-analysis and a single large trial (concordance of results was assumed if effects were in the same direction and the meta-analytic estimate was within 30% of the trial); analysis of funnel plots from 37 meta-analyses identified from a hand search of four leading general medicine journals 1993-6 and 38 meta-analyses from the second 1996 issue of the Cochrane Database of Systematic Reviews . Main outcome measure: Degree of funnel plot asymmetry as measured by the intercept from regression of standard normal deviates against precision. Results: In the eight pairs of meta-analysis and large trial that were identified (five from cardiovascular medicine, one from diabetic medicine, one from geriatric medicine, one from perinatal medicine) there were four concordant and four discordant pairs. In all cases discordance was due to meta-analyses showing larger effects. Funnel plot asymmetry was present in three out of four discordant pairs but in none of concordant pairs. In 14 (38%) journal meta-analyses and 5 (13%) Cochrane reviews, funnel plot asymmetry indicated that there was bias. Conclusions: A simple analysis of funnel plots provides a useful test for the likely presence of bias in meta-analyses, but as the capacity to detect bias will be limited when meta-analyses are based on a limited number of small trials the results from such analyses should be treated with considerable caution. Key messages Systematic reviews of randomised trials are the best strategy for appraising evidence; however, the findings of some meta-analyses were later contradicted by large trials Funnel plots, plots of the trials9 effect estimates against sample size, are skewed and asymmetrical in the presence of publication bias and other biases Funnel plot asymmetry, measured by regression analysis, predicts discordance of results when meta-analyses are compared with single large trials Funnel plot asymmetry was found in 38% of meta-analyses published in leading general medicine journals and in 13% of reviews from the Cochrane Database of Systematic Reviews Critical examination of systematic reviews for publication and related biases should be considered a routine procedure

37,989 citations

Journal ArticleDOI
TL;DR: In this review the usual methods applied in systematic reviews and meta-analyses are outlined, and the most common procedures for combining studies with binary outcomes are described, illustrating how they can be done using Stata commands.

31,656 citations

Journal ArticleDOI
TL;DR: A structured summary is provided including, as applicable, background, objectives, data sources, study eligibility criteria, participants, interventions, study appraisal and synthesis methods, results, limitations, conclusions and implications of key findings.

31,379 citations