Participant expectancies in double-blind randomized placebo-controlled trials: potential limitations to trial validity
Participant expectancies in double-blind randomized placebo-controlled trials: potential limitations to trial validity
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DOI：
10.1177/1740774510367916
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发表时间：
2010-06-01
期刊：
影响因子：
2.7
通讯作者：
Colagiuri, Ben
中科院分区：
文献类型：
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作者：
Colagiuri, Ben
随机对照试验（RCT）使用安慰剂对照达到双盲，目的是确定治疗效果超过预期和其他形式的偏倚。尽管如此，越来越多的研究表明，参与者的期望可以影响这些试验的结果。目的和方法这篇非系统性综述检查研究评估参与者的期望在双盲安慰剂对照随机对照试验中的作用，以确定他们是否以及如何限制这些类型的试验。结果似乎至少有三种方式，参与者的期望可以限制双盲安慰剂对照随机对照试验的有效性。设盲安慰剂对照RCT。首先，当盲法失败时，研究无法确定在接受积极治疗的组中观察到的任何改善是由于治疗的效果还是由于参与者的期望。其次，如果每个治疗组中存在强烈的安慰剂效应，则受试者的预期可能会产生天花板效应，这可能错误地表明没有预期的积极治疗无效。第三，知识的参与者将被分配积极治疗或安慰剂在双盲安慰剂对照随机对照试验可能会导致较弱的治疗反应比预期在标准的临床实践中，患者不太可能怀疑他们已经得到了积极的treatment.Conclusions参与者的期望可以破坏双盲安慰剂对照随机对照试验的有效性。进行这些试验的研究人员应该评估参与者对治疗分配的信念，并积极调查这些信念是否以及如何影响试验结果。临床试验2010; 7：246-255。http://ctj.sagepub.com.
Background Randomized controlled trials (RCTs) that use placebo controls to achieve double-blinding intend to establish the efficacy of a treatment over and above expectancy and other forms of bias. Despite this, a growing body of research suggests that participant expectancies can influence the outcomes of these trials.Purpose and Methods This nonsystematic review examines research assessing the role of participant expectancies in double-blind placebo-controlled RCTs in order to determine if and how they can limit these types of trials.Results There appear to be at least three ways in which participant expectancies can limit the validity of double-blind placebo-controlled RCTs. First, when blinding fails researches cannot determine whether any observed improvement in the group receiving active treatment resulted because of the treatment's effect or because of participants' expectancies. Second, participant expectancies could create ceiling effects if there are strong placebo effects in each treatment arm and this may falsely suggest that the active treatment is ineffective without expectancy. Third, the knowledge that a participant will be allocated active treatment or placebo in double-blind placebo-controlled RCTs is likely to lead to weaker treatment responses than would be expected in standard clinical practice, in which patients are unlikely to doubt that they have been given an active treatment.Conclusions Participants' expectancies can undermine the validity of double-blind placebo-controlled RCTs. Researchers conducting these trials should assess participants' beliefs about their treatment allocation and actively investigate if and how these beliefs may have influenced the trial's outcome. Clinical Trials 2010; 7: 246-255. http://ctj.sagepub.com.