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Biomedical subjects

I Chalmers

Publications and source records attributed to I Chalmers.

At least 55 records · Page 3Linked to original sources
PubMed1995

The methodologic quality of randomization as assessed from reports of trials in specialist and general medical journals.

OBJECTIVE: To assess the quality of randomization from reports of trials in a sample of specialist journals, and to compare those results with a similar assessment from a sample of general medical journals. DESIGN: Evaluation of all 206 reports of parallel-group randomized trials published in the 1990 and 1991 volumes of four journals of obstetrics and gynecology and of 81 reports of trials published during 1987 in four general medical journals. RESULTS: Of the reports published in the specialist and in the general medical journals, only 32% and 48%, respectively, reported having used an adequate method to generate random numbers; only 23% and 26%, respectively, contained information showing that steps had been taken to conceal assignment until the point of treatment allocation; and merely 9% and 15%, respectively, described adequate methods of both sequence generation and allocation concealment. In those reports of trials that had apparently used unrestricted randomization, the differences in sample sizes between treatment and control groups were much smaller than would be expected by chance, and that feature was more marked in the specialist journals. In reports of trials in which hypothesis tests had been used to compare baseline characteristics, only 2% of tests reported in specialist journals and 4% of tests reported in general journals were statistically significant, lower than the expected rate of 5%. CONCLUSIONS: Generating unbiased comparison groups requires proper randomization, yet the reports in these specialist and general journals usually provided inadequate or unacceptable information. Additional analyses suggest that nonrandom manipulation of comparison groups and selective reporting of baseline comparisons may have occurred.

Gynecology↗
PubMed1995

What do I want from health research and researchers when I am a patient?

I have attempted to adopt the perspective of a patient--albeit one with a rather atypical background--to explore what I want from health research and researchers. This has left me with the impression that health researchers could serve the interests of the public more effectively in a variety of ways, and that they would be helped to do so by greater lay involvement in planning and promoting health research.

Attitude to Health↗
PubMed1995

Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials.

OBJECTIVE: To determine if inadequate approaches to randomized controlled trial design and execution are associated with evidence of bias in estimating treatment effects. DESIGN: An observational study in which we assessed the methodological quality of 250 controlled trials from 33 meta-analyses and then analyzed, using multiple logistic regression models, the associations between those assessments and estimated treatment effects. DATA SOURCES: Meta-analyses from the Cochrane Pregnancy and Childbirth Database. MAIN OUTCOME MEASURES: The associations between estimates of treatment effects and inadequate allocation concealment, exclusions after randomization, and lack of double-blinding. RESULTS: Compared with trials in which authors reported adequately concealed treatment allocation, trials in which concealment was either inadequate or unclear (did not report or incompletely reported a concealment approach) yielded larger estimates of treatment effects (P < .001). Odds ratios were exaggerated by 41% for inadequately concealed trials and by 30% for unclearly concealed trials (adjusted for other aspects of quality). Trials in which participants had been excluded after randomization did not yield larger estimates of effects, but that lack of association may be due to incomplete reporting. Trials that were not double-blind also yielded larger estimates of effects (P = .01), with odds ratios being exaggerated by 17%. CONCLUSIONS: This study provides empirical evidence that inadequate methodological approaches in controlled trials, particularly those representing poor allocation concealment, are associated with bias. Readers of trial reports should be wary of these pitfalls, and investigators must improve their design, execution, and reporting of trials.

Bias↗
PubMed1995

Variability of skin scores and clinical measurements in scleroderma.

OBJECTIVE: To determine the variability of several clinical outcome measurements commonly used in scleroderma clinical trials. METHODS: Ten researchers, members of a multicenter placebo controlled trial of methotrexate in early diffuse scleroderma, studied the intraobserver and interobserver variability of variables used to assess efficacy in scleroderma trials. RESULTS: For most measures, the variability within an observer was less than that found between observers, and therefore the intraobserver reliability was better than the interobserver reliability. The reliability of the modified Rodnan skin score exceeded the Rodnan skin score. Measures with inherent interpretation such as global assessments and skin scores had more variability than easily performed measurements such as grip strength and oral opening. CONCLUSION: Some of our variability was higher than variability previously reported; this could be due to the large number of examiners and patients in our study.

Female↗
PubMed1994

Reporting, updating, and correcting systematic reviews of the effects of health care.

The recent growth in the numbers of published systematic reviews reflects growing recognition of their importance for improving knowledge about the effects of health care. In Britain the NHS R&D Programme has established two centres to prepare systematic reviews of existing information, and the Cochrane Collaboration--an international network of individuals and institutions--evolved to produce systematic, periodically updated reviews of randomised controlled trials. The large amount of existing evidence that needs to be considered creates a problem for the reporting of systematic reviews: the need to ensure that methods and results of systematic reviews are adequately described has to be reconciled with the limited space available in printed journals. A possible solution is the use of electronic publications: reviews could be published simultaneously in a short, printed form and in a more detailed electronic form. Electronic publications also have the advantage of the ease with which reviews may be updated as new evidence becomes available or mistakes are identified.

Health Services Research↗
PubMed1994

Assessing the quality of randomization from reports of controlled trials published in obstetrics and gynecology journals.

OBJECTIVE: To assess the methodologic quality of approaches used to allocate participants to comparison groups in randomized controlled trials from one medical specialty. DESIGN: Survey of published, parallel group randomized controlled trials. DATA SOURCES: All 206 reports with allocation described as randomized from the 1990 and 1991 volumes of four journals of obstetrics and gynecology. MAIN OUTCOME MEASURES: Direct and indirect measures of the adequacy of randomization and baseline comparisons. RESULTS: Only 32% of the reports described an adequate method for generating a sequence of random numbers, and only 23% contained information showing that steps had been taken to conceal assignment until the point of treatment allocation. A mere 9% described both sequence generation and allocation concealment. In reports of trials that had apparently used unrestricted randomization, the differences in sample sizes between treatment and control groups were much smaller than would be expected due to chance. In reports of trials in which hypothesis tests had been used to compare baseline characteristics, only 2% of reported test results were statistically significant, lower than the expected rate of 5%. CONCLUSIONS: Proper randomization is required to generate unbiased comparison groups in controlled trials, yet the reports in these journals usually provided inadequate or unacceptable information on treatment allocation. Additional analyses suggest that nonrandom manipulation of comparison groups and selective reporting of baseline comparisons may have occurred.

Gynecology↗
PubMed1994

Is there a case for an international medical scientific press council?

Serious abuse of editorial power is rarely publicized, but evidence that it occurs is accumulating. Authors who believe that they have been dealt with unfairly have little possibility of a hearing of their complaint, and cases cannot easily be publicized because of fears of legal action. We describe briefly three cases in which the alleged misdeeds indicate that there were legitimate questions that needed answers. In the first case, an editor republished a previously published article without the authors' permission (but stated the opposite), attacked it in an accompanying editorial, and then denied the authors the right of reply. The other cases concerned a commissioned review article that was plagiarized and an editor with an undisclosed vested interest. An appeal process is needed for authors who think that they are victims of editorial abuse of power. We suggest that the International Committee of Medical Journal Editors turn its attention to editorial misconduct and explore possible procedures for allowing authors' grievances to be heard and for possible sanctions if complaints are upheld. An International Medical Scientific Press Council might be established to produce a code of conduct for editors and a corresponding taxonomy of inappropriate editorial behavior.

Advisory Committees↗
PubMed1993

The Cochrane collaboration: preparing, maintaining, and disseminating systematic reviews of the effects of health care.

In an influential book published more than twenty years ago, Archie Cochrane drew attention to our great collective ignorance about the effects of health care, and explained how evidence from randomized controlled trials (RCTs) could help us to use resources more rationally. He recognized that people who want to take more informed decisions about health care do not have ready access to reliable reviews of the available evidence. In 1979, he wrote: "It is surely a great criticism of our profession that we have not organised a critical summary, by specialty or subspecialty, adapted periodically, of all relevant randomised controlled trials." The Cochrane Collaboration has evolved in response to this challenge and will eventually cover all areas of health care. Contributors in many countries and specialties are preparing and maintaining systematic reviews of RCTs, and reviews of other evidence when appropriate. These reviews will be disseminated using electronic media through the Cochrane Database of Systematic Reviews.

Databases, Factual↗