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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.


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Journal ArticleDOI
TL;DR: To elucidate potential bias sources in meta-analyses, it is studied whether the effect of nonsteroidal, anti-inflammatory drugs on joint count in patients with rheumatoid arthritis was related to trial design, sample size, duration of treatment, drop-out rate, and meta-analytic technique.
Abstract: Gotzsche PC. Meta-analysis of NSAIDs: Contribution of Drugs, Doses, Trial Designs, and Meta-analytic Techniques. Scand J Rheumatol 1993; 22: 255–260.To elucidate potential bias sources in meta-analyses, I studied whether the effect of nonsteroidal, anti-inflammatory drugs on joint count in patients with rheumatoid arthritis was related to trial design (active or placebo control), sample size, duration of treatment, drop-out rate, the existence of a wash-in period, drug, dose, and meta-analytic technique.In short-term trials, none of the covariates was related to the effect size. No differences between drugs or doses were found in usual gold standard meta-analyses, comparing drugs within trials before pooling. In a meta-analysis of treatment arms, however, four drugs were either significantly more or less effective than average, but these deviations were spurious.In meta-analyses of NSAIDs, indirect comparisons may allow a preliminary comparison of drugs that have not been compared directly. Treatment arms...

24 citations

Journal ArticleDOI
TL;DR: No evidence was found to assess the benefits and harms of screening with urinary dipsticks, which remain unknown, and no studies were eligible for inclusion.
Abstract: Background Urinary dipsticks are sometimes used for screening asymptomatic people, and for case-finding among inpatients or outpatients who do not have genitourinary symptoms. Abnormalities identified on screening sometimes lead to additional investigations, which may identify serious disease, such as bladder cancer and chronic kidney disease (CKD). Urinary dipstick screening could improve prognoses due to earlier detection, but could also lead to unnecessary and potentially invasive follow-up testing and unnecessary treatment. Objectives We aimed to quantify the benefits and harms of screening with urinary dipsticks in general populations and patients in hospitals. Search methods We searched the Cochrane Renal Group's Specialised Register to 8 September 2014 through contact with the Trials Search Co-ordinator using search terms relevant to this review. Selection criteria Randomised controlled trials and other study types that compared urinary dipstick screening with no dipstick screening were eligible for inclusion. We searched for studies that investigated the use of urinary dipsticks for detecting haemoglobin, protein, albumin, albumin-creatinine ratio, leukocytes, nitrite, or glucose, alone or in any combination, and in any setting. We planned to exclude studies conducted in patients with urinary disorders. Data collection and analysis It was planned that two authors would independently extract data from included studies and assess risk of bias using the Cochrane risk of bias tool. However, no studies met our inclusion criteria. Main results Literature searches to 8 September 2014 yielded 4298 records, of which 4249 were excluded following title and abstract assessment. There were 49 records (44 studies) eligible for full text assessment; of these 18 studies were not RCTs and 26 studies compared interventions or controls that were not relevant to this review. Thus, no studies were eligible for inclusion. Authors' conclusions We found no evidence to assess the benefits and harms of screening with urinary dipsticks, which remain unknown.

23 citations

Journal ArticleDOI
TL;DR: This work believes it came close to indexing complete HPV vaccine study programmes, but only one of the four manufacturers provided information for the index and a fifth of the index could not be cross-verified.
Abstract: Unabridged access to drug industry and regulatory trial registers and data reduces reporting bias in systematic reviews and may provide a complete index of a drug’s clinical study programme. Currently, there is no public index of the human papillomavirus (HPV) vaccine industry study programmes or a public index of non-industry funded studies. By cross-verification via study programme enquiries to the HPV vaccine manufacturers and regulators and searches of trial registers and journal publication databases, we indexed clinical HPV vaccine studies as a basis to address reporting bias in a systematic review of clinical study reports. We indexed 206 clinical studies: 145 industry and 61 non-industry funded studies. One of the four HPV vaccine manufacturers (GlaxoSmithKline) provided information on its study programme. Most studies were cross-verified from two or more sources (160/206, 78%) and listed on regulatory or industry trial registers or journal publication databases (195/206, 95%)—in particular, on ClinicalTrials.gov (176/195, 90%). However, study results were only posted for about half of the completed studies on ClinicalTrials.gov (71/147, 48%). Two thirds of the industry studies had a study programme ID, manufacturer specific ID, and national clinical trial (NCT) ID (91/145, 63%). Journal publications were available in journal publication databases (the Cochrane Collaboration’s Central Register of Controlled Trials, Google Scholar and PubMed) for two thirds of the completed studies (92/149, 62%). We believe we came close to indexing complete HPV vaccine study programmes, but only one of the four manufacturers provided information for our index and a fifth of the index could not be cross-verified. However, we indexed larger study programmes than those listed by major regulators (i.e., the EMA and FDA that based their HPV vaccine approvals on only half of the available trials). To reduce reporting bias in systematic reviews, we advocate the registration and publication of all studies and data in the public domain.

23 citations

Journal ArticleDOI
TL;DR: In this article, the authors explored whether general medical and specialty journals differed in accepting the results and methods of three Cochrane reviews on mammography screening, and whether the methods and results were accepted (explicit agreement or quoted without caveats).
Abstract: Introduction In 2001, a Cochrane review of mammography screening questioned whether screening reduces breast cancer mortality, and a more comprehensive review in Lancet , also in 2001, reported considerable overdiagnosis and overtreatment. This led to a heated debate and a recent review of the evidence by UK experts intended to be independent. Objective To explore if general medical and specialty journals differed in accepting the results and methods of three Cochrane reviews on mammography screening. Methods We identified articles citing the Lancet review from 2001 or updated versions of the Cochrane review (last search 20 April 2012). We explored which results were quoted, whether the methods and results were accepted (explicit agreement or quoted without caveats), differences between general and specialty journals, and change over time. Results We included 171 articles. The results for overdiagnosis were not quoted in 87% (148/171) of included articles and the results for breast cancer mortality were not quoted in 53% (91/171) of articles. 11% (7/63) of articles in general medical journals accepted the results for overdiagnosis compared with 3% (3/108) in specialty journals (p=0.05). 14% (9/63) of articles in general medical journals accepted the methods of the review compared with 1% (1/108) in specialty journals (p=0.001). Specialty journals were more likely to explicitly reject the estimated effect on breast cancer mortality 26% (28/108), compared with 8% (5/63) in general medical journals, p=0.02. Conclusions Articles in specialty journals were more likely to explicitly reject results from the Cochrane reviews, and less likely to accept the results and methods, than articles in general medical journals. Several specialty journals are published by interest groups and some authors have vested interests in mammography screening.

22 citations


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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