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The randomised clinical trial is the most reliable study design to compare the effects of different interventions, however, the methodological quality of randomised clinical trials varies. In this review, the central considerations for critically appraising a randomised clinical trial are described along with an example, terminological references, description of design variants and reporting guidelines and appraisal tools. This review aims at helping clinicians and other users of randomised clinical trials to assess the trustworthiness and relevance of trial results for their own practice., (Published under Open Access CC-BY-NC-BD 4.0. https://creativecommons.org/licenses/by-nc-nd/4.0/.)

We analysed the scientific impact of systematic reviews and randomised trials published in the BMJ Christmas issues 1997-2006. The articles were mostly interpreted correctly as humorous, but the humorous dimension was overlooked with surprising ease. The result from one ironic-absurd trial on the effect of retroactive remote intercessory prayer for patients already dead or dismissed was taken at face value in 12/36 of the citing articles, and mortality data was unconditionally included in three systematic reviews. Thus, we document a new type of bias in medical research: Serious Idiopathic Loss of Ludic ironY (SILLY) bias, both in citation practices and in metaanalyses.

In 22 of 44 industry-initiated clinical trial protocols from 1994-95, it was noted that the sponsor either owned the data or needed to approve the manuscript; another 18 protocols had other constraints. Furthermore, in 16 trials, the sponsor had access to accumulating data, and in an additional 16 trials the sponsor could stop the trial at any time, for any reason. These facts were not noted in any of the trial reports. We found similar constraints on publication rights in 44 protocols from 2004. This tight sponsor control over industry-initiated trials should be changed.

Introduction: Selective reporting of positive outcomes is associated with bias., Materials and Methods: We conducted a cohort study of 102 protocols of randomised trials approved by the Scientific Ethics Committees for Copenhagen and Frederiksberg in 1994-1995 and the corresponding 122 reports., Results: The median proportion of incompletely reported outcomes per trial was 50%. Statistically significant outcomes were more often fully reported, odds ratio 2.4. In 62% of trials, at least one primary outcome was changed., Discussion: Outcomes in randomised trials are often reported selectively.

Introduction: Placebo treatments have been reported to help patients with many diseases, but the quality of the evidence supporting this belief has not been rigorously evaluated., Material and Methods: We conducted a systematic review of clinical trials in which patients were randomised either to placebo treatment or to no treatment. A placebo intervention could be pharmacological (for instance, a tablet), physical (for instance manipulation), or psychological (for instance conversation)., Results: We identified 130 trials that met our inclusion criteria. After excluding 16, which gave no relevant outcome data, 32 with binary outcomes and 82 with continuous outcomes were left. As compared to no treatment, placebo had no significant effect on binary outcomes, the pooled relative risk was 0.95 (95% confidence interval 0.88 to 1.02), irrespective of whether these outcomes were subjective or objective. Placebo seemed to have a beneficial effect in the trials with continuous outcomes, the overall pooled standardised mean difference of the placebo and no-treatment groups was -0.28 (-0.38 to -0.19), but the effect decreased with increasing sample size, which indicates bias. The pooled standardised mean difference was significant for the trials with subjective outcomes, -0.36 (-0.47 to -0.25), but not for those with objective outcomes, -0.12 (-0.27 to 0.03). In trials involving the treatment of pain, placebo was reported to have a moderate beneficial effect, with a pooled standardised mean difference of -0.27 (-0.40 to -0.15), but bias, for instance reporting bias, was possible., Conclusion: We found no reliable evidence that placebo treatments in general had effects of clinical importance.