Psychology, University of Southampton, Southampton, Hampshire, United Kingdom.
PLoS One. 2012;7(6):e39661. doi: 10.1371/journal.pone.0039661. Epub 2012 Jun 27.
Placebo groups are used in randomised clinical trials (RCTs) to control for placebo effects, which can be large. Participants in trials can misunderstand written information particularly regarding technical aspects of trial design such as randomisation; the adequacy of written information about placebos has not been explored. We aimed to identify what participants in major RCTs in the UK are told about placebos and their effects.
We conducted a content analysis of 45 Participant Information Leaflets (PILs) using quantitative and qualitative methodologies. PILs were obtained from trials on a major registry of current UK clinical trials (the UKCRN database). Eligible leaflets were received from 44 non-commercial trials but only 1 commercial trial. The main limitation is the low response rate (13.5%), but characteristics of included trials were broadly representative of all non-commercial trials on the database. 84% of PILs were for trials with 50:50 randomisation ratios yet in almost every comparison the target treatments were prioritized over the placebos. Placebos were referred to significantly less frequently than target treatments (7 vs. 27 mentions, p<001) and were significantly less likely than target treatments to be described as triggering either beneficial effects (1 vs. 45, p<001) or adverse effects (4 vs. 39, p<001). 8 PILs (18%) explicitly stated that the placebo treatment was either undesirable or ineffective.
PILs from recent high quality clinical trials emphasise the benefits and adverse effects of the target treatment, while largely ignoring the possible effects of the placebo. Thus they provide incomplete and at times inaccurate information about placebos. Trial participants should be more fully informed about the health changes that they might experience from a placebo. To do otherwise jeopardises informed consent and is inconsistent with not only the science of placebos but also the fundamental rationale underpinning placebo controlled trials.
安慰剂组被用于随机临床试验 (RCTs) 以控制安慰剂效应，而安慰剂效应可能很大。参与者可能会误解关于试验设计的书面信息，特别是关于随机化等技术方面的信息；关于安慰剂的书面信息是否充分尚未得到探索。我们旨在确定英国主要 RCT 中参与者被告知的有关安慰剂及其作用的内容。
我们使用定量和定性方法对 45 份参与者信息传单 (PIL) 进行了内容分析。PIL 从英国当前临床试验主要注册处 (UKCRN 数据库) 的试验中获得。从 44 项非商业试验中获得了合格的传单，但只有 1 项商业试验。主要限制是低响应率 (13.5%)，但纳入试验的特征广泛代表了数据库中所有非商业试验。84%的 PIL 是针对 50:50 随机化比例的试验，但在几乎所有比较中，目标治疗都优先于安慰剂。安慰剂的提及频率明显低于目标治疗 (7 次与 27 次，p<0.01)，并且与目标治疗相比，被描述为引发有益效果 (1 次与 45 次，p<0.01)或不良效果 (4 次与 39 次，p<0.01)的可能性明显较低。8 份 PIL(18%)明确表示安慰剂治疗既不理想也无效。
来自最近高质量临床试验的 PIL 强调了目标治疗的益处和不良反应，而在很大程度上忽略了安慰剂的可能作用。因此，它们提供了关于安慰剂的不完整且有时不准确的信息。试验参与者应更全面地了解他们可能从安慰剂中经历的健康变化。否则，知情同意就会受到威胁，这不仅与安慰剂的科学不一致，也与安慰剂对照试验的基本原理不一致。
