Showing papers in "BMC Medical Research Methodology in 2001"
TL;DR: The revised CONSORT statement is intended to improve the reporting of an RCT, enabling readers to understand a trial's conduct and to assess the validity of its results.
Abstract: To comprehend the results of a randomized controlled trial (RCT), readers must understand its design, conduct, analysis and interpretation. That goal can only be achieved through complete transparency from authors. Despite several decades of educational efforts, the reporting of RCTs needs improvement. Investigators and editors developed the original CONSORT (Consolidated Standards of Reporting Trials) statement to help authors improve reporting by using a checklist and flow diagram. The revised CONSORT statement presented in this paper incorporates new evidence and addresses some criticisms of the original statement.
2,444 citations
TL;DR: Percentage change from baseline should not be used in statistical analysis and trialists wishing to report this statistic should use another method, such as ANCOVA, and convert the results to a percentage change by using mean baseline scores.
Abstract: Many randomized trials involve measuring a continuous outcome - such as pain, body weight or blood pressure - at baseline and after treatment. In this paper, I compare four possibilities for how such trials can be analyzed: post-treatment; change between baseline and post-treatment; percentage change between baseline and post-treatment and analysis of covariance (ANCOVA) with baseline score as a covariate. The statistical power of each method was determined for a hypothetical randomized trial under a range of correlations between baseline and post-treatment scores. ANCOVA has the highest statistical power. Change from baseline has acceptable power when correlation between baseline and post-treatment scores is high;when correlation is low, analyzing only post-treatment scores has reasonable power. Percentage change from baseline has the lowest statistical power and was highly sensitive to changes in variance. Theoretical considerations suggest that percentage change from baseline will also fail to protect from bias in the case of baseline imbalance and will lead to an excess of trials with non-normally distributed outcome data. Percentage change from baseline should not be used in statistical analysis. Trialists wishing to report this statistic should use another method, such as ANCOVA, and convert the results to a percentage change by using mean baseline scores.
445 citations
TL;DR: Specific search strategies based on adverse effects textwords and indexing terms will fail to identify nearly a quarter of trials that report on the rate of drug adverse effects.
Abstract: Background: We would expect information on adverse drug reactions in randomised clinical trials to be easily retrievable from specific searches of electronic databases. However, complete retrieval of such information may not be straightforward, for two reasons. First, not all clinical drug trials provide data on the frequency of adverse effects. Secondly, not all electronic records of trials include terms in the abstract or indexing fields that enable us to select those with adverse effects data. We have determined how often automated search methods, using indexing terms and/or textwords in the title or abstract, would fail to retrieve trials with adverse effects data. Methods: We used a sample set of 107 trials known to report frequencies of adverse drug effects, and measured the proportion that (i) were not assigned the appropriate adverse effects indexing terms in the electronic databases, and (ii) did not contain identifiable adverse effects textwords in the title or abstract. Results: Of the 81 trials with records on both MEDLINE and EMBASE, 25 were not indexed for adverse effects in either database. Twenty-six trials were indexed in one database but not the other. Only 66 of the 107 trials reporting adverse effects data mentioned this in the abstract or title of the paper. Simultaneous use of textword and indexing terms retrieved only 82/107 (77%) papers. Conclusions: Specific search strategies based on adverse effects textwords and indexing terms will fail to identify nearly a quarter of trials that report on the rate of drug adverse effects.
103 citations
TL;DR: Different designs of high quality trials can be used to support limited information used in meta-analysis without recourse to low quality trials that might be biased.
Abstract: Meta-analysis usually restricts the information pooled, for instance using only randomised, double-blind, placebo-controlled trials. This neglects other types of high quality information. This review explores using different information for the combination of paracetamol 1000 mg and codeine 60 mg in acute postoperative pain.
58 citations
TL;DR: Despite some recent improvement, reporting of conflicts of interest in clinical guidelines published in influential journals is largely neglected.
Abstract: Background
Guidelines published in major medical journals are very influential in determining clinical practice. It would be essential to evaluate whether conflicts of interests are disclosed in these publications. We evaluated the reporting of conflicts of interest and the factors that may affect such disclosure in a sample of 191 guidelines on therapeutic and/or preventive measures published in 6 major clinical journals (Annals of Internal Medicine, BMJ, JAMA, Lancet, New England Journal of Medicine, Pediatrics) in 1979, 1984, 1989, 1994 and 1999.
55 citations
TL;DR: The paired availability design has promise for evaluating medical versus surgical interventions, in which it is difficult to recruit patients to a randomized trial.
Abstract: Background
Although a randomized trial represents the most rigorous method of evaluating a medical intervention, some interventions would be extremely difficult to evaluate using this study design. One alternative, an observational cohort study, can give biased results if it is not possible to adjust for all relevant risk factors.
34 citations
TL;DR: The fate and popularity of large trials may determine the overall recruitment of multicenter groups and modeling of enrollment rates may be used to comprehend long-term patterns and to perform future strategic planning.
Abstract: Background
We examined whether quarterly patient enrollment in a large multicenter clinical trials group could be modeled in terms of predictors including time parameters (such as long-term trends and seasonality), the effect of large trials and the number of new studies launched each quarter. We used the database of all clinical studies launched by the AIDS Clinical Trials Group (ACTG) between October 1986 and November 1999. Analyses were performed in two datasets: one included all studies and substudies (n = 475, total enrollment 69,992 patients) and the other included only main studies (n = 352, total enrollment 57,563 patients).
30 citations
TL;DR: North-American contributions and reports with statistically positive results have higher acceptance rates at the AGA and formal abstract quality was also predictive for acceptance.
Abstract: Background
The Digestive Diseases Week (DDW) is the major meeting for presentation of research in gastroenterology. The acceptance of an abstract for presentation at this meeting is the most important determinant of subsequent full publication. We wished to examine the determinants of abstract acceptance for this meeting.
25 citations
TL;DR: The use of high quality paper did not increase response rates to a questionnaire survey of gynaecologists affiliated to an endoscopic society.
Abstract: Background
Response rates to surveys are declining and this threatens the validity and generalisability of their findings. We wanted to determine whether paper quality influences the response rate to postal surveys
21 citations
TL;DR: Software is now available for computing adjusted sample sizes for case-control designs and the effect of potential disease-exposure-confounder interaction may be explored.
Abstract: Background
Published formulas for case-control designs provide sample sizes required to determine that a given disease-exposure odds ratio is significantly different from one, adjusting for a potential confounder and possible interaction.
21 citations
TL;DR: Updating the meta-analyses lead to a more precise estimate of the likely effect of the nicotine patch, but the clinical message was unchanged and further placebo controlled NRT trials are not likely to add to the evidence base.
Abstract: To examine the effect of updating a systematic review of nicotine replacement therapy on its contents and conclusions. We examined the effects of regular updating of a systematic review of nicotine replacement therapy for smoking cessation. We considered two outcomes. First, we assessed the effect of adding new data to meta-analyses, comparing results in 2000 with the results in 1994. Second, we assessed qualitatively the ways inwhich the nature of the questions addressed by the review had changed between the two dates. For the first outcome, we compared the number of trials, the pooled estimate of effect using the odds ratio, and the results of pre-specified subgroup analyses, for nicotine gum and patch separately. Using a test for interaction, we assessed whether differences between estimates were statistically significant. There were ten new trials of nicotine gum between 1994 and 2000, and the meta-analytic effect changed little. For the nicotine patch the number of trials increased from 9 to 30, and the meta-analytic effect fell from 2.07 (95% CI 1.64 – 2.62) to 1.73 (95% CI 1.56 – 1.93). Apparent differences in relative effect in sub-groups found in 1994 were not found in 2000. The updated systematic review addressed a number of questions not identified in the original version. Updating the meta-analyses lead to a more precise estimate of the likely effect of the nicotine patch, but the clinical message was unchanged. Further placebo controlled NRT trials are not likely to add to the evidence base. It is questionable whether updating the meta-analyses to include them is worthwhile. The content of the systematic review has, however, changed, with the addition of data addressing questions not considered in the original review. There is a tension between the principle of identifying the important questions prior to conducting a review, and keeping the review up to date as primary research identifies new avenues of enquiry.
TL;DR: The proposed parameter for quantifying the probability that a new therapy is cost-effective is superior to the acceptability curve because it is not sample size dependent and because it can be interpreted as the proportion of patients who would benefit if given the new therapy.
Abstract: Background
Acceptability curves have been proposed for quantifying the probability that a treatment under investigation in a clinical trial is cost-effective. Various definitions and estimation methods have been proposed. Loosely speaking, all the definitions, Bayesian or otherwise, relate to the probability that the treatment under consideration is cost-effective as a function of the value placed on a unit of effectiveness. These definitions are, in fact, expressions of the certainty with which the current evidence would lead us to believe that the treatment under consideration is cost-effective, and are dependent on the amount of evidence (i.e. sample size).
TL;DR: This patient preference combined with the reported accuracy of white cell scanning further establishes the usefulness of this means of IBD diagnosis.
Abstract: Background
In order to assess the usefulness of radiolabeled white cell scanning in the diagnosis of intestinal inflammation, subjects were asked to rank several dimensions of preference for white cell scanning in relation to other diagnostic tests. Two groups were surveyed: one known to have inflammatory bowel disease and the second not familiar in most cases with the tests. Subjects were asked to rank preference for each of seven tests: radiolabeled white cell scan, colonoscopy, barium enema, sigmoidoscopy, enteroclysis, stool analysis and laparotomy for the diagnosis of IBD and impressions of discomfort, embarrassment, inconvenience and danger related to each test. Mean rank scores were calculated, test ranks compared within groups and significance determined by the Wilcoxon rank test.
TL;DR: The undertaking of a multicentre project implies the need to work with a heterogeneous research team and yet at the same time attain a common goal by following a homogeneous methodology, which demands an additional effort on quality control.
Abstract: Background
The Multicentre Project for Tuberculosis Research (MPTR) was a clinical-epidemiological study on tuberculosis carried out in Spain from 1996 to 1998. In total, 96 centres scattered all over the country participated in the project, 19935 "possible cases" of tuberculosis were examined and 10053 finally included. Data-handling and quality control procedures implemented in the MPTR are described.