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Biomedical subjects

Peter C Gøtzsche

Publications and source records attributed to Peter C Gøtzsche.

At least 55 records · Page 3Linked to original sources
PubMed2005

The journal impact factor as a predictor of trial quality and outcomes: cohort study of hepatobiliary randomized clinical trials.

OBJECTIVES: To examine the association between the impact factor and characteristics of hepatobiliary randomized clinical trials. METHODS: A cohort study of 530 hepatobiliary randomized clinical trials was performed. The journal impact factor was extracted from Science Citation Index. For each trial, we extracted the sample size, the quality of randomization and blinding methods, and the statistical significance of the primary outcome measure. RESULTS: The median sample size was 45 participants (interquartile range 25-88). The allocation sequence generation was adequate in 273 trials (52%). Allocation concealment was adequate in 178 trials (34%). The primary outcome measure was statistically significant in 374 (71%) trials. Nonparametric analyses for trend indicated that the impact factor was significantly associated with the sample size (p < 0.01) and the proportion of trials with adequate allocation sequence generation (p < 0.01) or allocation concealment (p= 0.02). The impact factor was not significantly associated with the study outcome (p= 0.28). CONCLUSIONS: The present study supports the use of the impact factor as a rough quality indicator. However, even trials in high impact journals may be small or may have inadequate quality. Critical appraisal of individual trials is always necessary, irrespective of the place of publication.

Bibliometrics↗
PubMed2005

Physical activity for secondary prevention of disease. Systematic reviews of randomised clinical trials.

BACKGROUND: Physical activity is recommended for secondary prevention of several diseases but it is not always clear how reliable the evidence is. METHODS: We searched MEDLINE and The Cochrane Library for systematic reviews of randomised clinical trials published 1998-2004. RESULTS: We identified 30 eligible systematic reviews and excluded 13 that contained trials covered in larger reviews or were older than other reviews on the same subject. Physical activity decreased all-cause mortality in patients with coronary heart disease, odds ratio 0.73 (95% confidence interval 0.54 to 0.98), increased maximum walking time in patients with intermittent claudication by 6.5 min (4.4 to 8.7), and decreased pain in patients with osteoarthritis of the knee, standardised mean difference 0.34 (0.24 to 0.44). There were positive effects also in heart failure, chronic obstructive lung disease, type 2 diabetes and fibromyalgia, but they need confirmation in high-quality trials. Exercise improved quality of life in several conditions and generally led to improved physical performance. An effect was not shown in stroke, asthma, rheumatoid arthritis, acute or chronic low back pain, chronic fatigue syndrome, depression, cystic fibrosis or HIV/AIDS. The occurrence of harms was generally not reported. CONCLUSION: Physical activity can have important, and even life-saving, effects as secondary prevention of disease, but more and better trials are needed to fully assess its benefits and harms, in particular trials that compare exercise with drugs.

Exercise Therapy↗
PubMed2004

Better reporting of harms in randomized trials: an extension of the CONSORT statement.

In response to overwhelming evidence and the consequences of poor-quality reporting of randomized, controlled trials (RCTs), many medical journals and editorial groups have now endorsed the CONSORT (Consolidated Standards of Reporting Trials) statement, a 22-item checklist and flow diagram. Because CONSORT primarily aimed at improving the quality of reporting of efficacy, only 1 checklist item specifically addressed the reporting of safety. Considerable evidence suggests that reporting of harms-related data from RCTs also needs improvement. Members of the CONSORT Group, including journal editors and scientists, met in Montebello, Quebec, Canada, in May 2003 to address this problem. The result is the following document: the standard CONSORT checklist with 10 new recommendations about reporting harms-related issues, accompanying explanation, and examples to highlight specific aspects of proper reporting. We hope that this document, in conjunction with other CONSORT-related materials (http://www.consort-statement.org), will help authors improve their reporting of harms-related data from RCTs. Better reporting will help readers critically appraise and interpret trial results. Journals can support this goal by revising Instructions to Authors so that they refer authors to this document.

Evidence-Based Medicine↗
PubMed2004

Polyclonal immunoglobulin for treatment of bacterial sepsis: a systematic review.

Randomized trials of adjunctive treatment of bacterial sepsis with polyclonal immunoglobulin show conflicting results. We performed a systematic review and a meta-analysis of the results of randomized trials that compared reductions in mortality rates in patient groups treated with polyclonal immunoglobulin versus either placebo or no treatment in addition to conventional treatment. High-quality trials had adequate concealment of allocation, were double-blinded and placebo-controlled, and made data available for intention-to-treat analyses. Twenty trials were included. Meta-analysis of all trials showed a relative risk of death with immunoglobulin treatment of 0.77 (95% confidence interval [CI], 0.68-0.88). High-quality trials (involving a total of 763 patients, 255 of whom died) showed a relative risk of 1.02 (95% CI, 0.84-1.24), whereas other trials (involving a total of 948 patients, 292 of whom died) showed a relative risk of 0.61 (95% CI, 0.50-0.73). Because high-quality trials failed to demonstrate a reduction in mortality, polyclonal immunoglobulin should not be used for treatment of sepsis except in randomized clinical trials.

Bacteremia↗
PubMed2004

Empirical evidence for selective reporting of outcomes in randomized trials: comparison of protocols to published articles.

CONTEXT: Selective reporting of outcomes within published studies based on the nature or direction of their results has been widely suspected, but direct evidence of such bias is currently limited to case reports. OBJECTIVE: To study empirically the extent and nature of outcome reporting bias in a cohort of randomized trials. DESIGN: Cohort study using protocols and published reports of randomized trials approved by the Scientific-Ethical Committees for Copenhagen and Frederiksberg, Denmark, in 1994-1995. The number and characteristics of reported and unreported trial outcomes were recorded from protocols, journal articles, and a survey of trialists. An outcome was considered incompletely reported if insufficient data were presented in the published articles for meta-analysis. Odds ratios relating the completeness of outcome reporting to statistical significance were calculated for each trial and then pooled to provide an overall estimate of bias. Protocols and published articles were also compared to identify discrepancies in primary outcomes. MAIN OUTCOME MEASURES: Completeness of reporting of efficacy and harm outcomes and of statistically significant vs nonsignificant outcomes; consistency between primary outcomes defined in the most recent protocols and those defined in published articles. RESULTS: One hundred two trials with 122 published journal articles and 3736 outcomes were identified. Overall, 50% of efficacy and 65% of harm outcomes per trial were incompletely reported. Statistically significant outcomes had a higher odds of being fully reported compared with nonsignificant outcomes for both efficacy (pooled odds ratio, 2.4; 95% confidence interval [CI], 1.4-4.0) and harm (pooled odds ratio, 4.7; 95% CI, 1.8-12.0) data. In comparing published articles with protocols, 62% of trials had at least 1 primary outcome that was changed, introduced, or omitted. Eighty-six percent of survey responders (42/49) denied the existence of unreported outcomes despite clear evidence to the contrary. CONCLUSIONS: The reporting of trial outcomes is not only frequently incomplete but also biased and inconsistent with protocols. Published articles, as well as reviews that incorporate them, may therefore be unreliable and overestimate the benefits of an intervention. To ensure transparency, planned trials should be registered and protocols should be made publicly available prior to trial completion.

Clinical Protocols↗
PubMed2004

Presentation on websites of possible benefits and harms from screening for breast cancer: cross sectional study.

OBJECTIVE: To investigate whether information on mammographic screening presented on websites by interest groups is balanced, is independent of source of funding, and reflects recent findings. DESIGN: Cross sectional study using a checklist with 17 information items. SETTING: 27 websites in Scandinavian and English speaking countries. RESULTS: The 13 sites from advocacy groups and the 11 from governmental institutions all recommended mammographic screening, whereas the three from consumer organisations questioned screening (P = 0.0007). All the advocacy groups accepted industry funding, apparently without restrictions. In contrast the three consumer organisations acknowledged the risk of bias related to industry funding, and two of them did not accept such funding at all. Advocacy groups and governmental organisations favoured information items that shed positive light on screening. The major harms of screening, overdiagnosis and overtreatment, were mentioned by only four of these groups, but by all three sites from consumer organisations (P = 0.02). In addition, the chosen information was often misleading or erroneous. The selection of information items for websites did not reflect recent findings, apart from the consumer sites, which were much more balanced and comprehensive than other sites (median of 9 information items v 3 items, P = 0.03). CONCLUSIONS: The information material provided by professional advocacy groups and governmental organisations is information poor and severely biased in favour of screening. Few websites live up to accepted standards for informed consent such as those stated in the General Medical Council's guidelines.

Bias↗
PubMed2004

Antibody response to Pseudomonas aeruginosa in cystic fibrosis patients: a marker of therapeutic success?--A 30-year cohort study of survival in Danish CF patients after onset of chronic P. aeruginosa lung infection.

We studied the effects of increasingly intensive treatment regimens on anti-pseudomonal antibody response and survival in five successive cohorts of a total of 157 Danish cystic fibrosis patients after they had acquired chronic P. aeruginosa lung infection. The time periods were 1971-1975 (N = 21), 1976-1980 (N = 64), 1981-1986 (N = 27), 1987-1993 (N = 26), and 1994-2000 (N = 19). During this 30-year period, we introduced elective 2-week courses of chemotherapy every third month in all chronically infected patients, early aggressive treatment with inhalation of colistin and oral ciprofloxacin for 3 months whenever P. aeruginosa was cultured in sputum from noncolonized patients, and inhalation of recombinant human dornase alfa. There was a significant correlation between the calendar year when chronic P. aeruginosa infection was acquired and the subsequent increase in the level of precipitins (P < 0.00001). The median number of precipitins increased by 5 per year in the oldest calendar year cohort, and 1 per year in the youngest. The median age of onset of chronic P. aeruginosa increased from 9.3 years from 1981-1986 to 13.8 years from 1987-2000. Survival after acquisition of chronic P. aeruginosa lung infection improved with time (P = 0.008). Our study shows that CF patients who are treated intensively have lower antibody responses and longer survival after acquisition of chronic P. aeruginosa lung infection.

Anti-Bacterial Agents↗