Sahota Inderjeet, Sheldon Robert, Pournazari Payam
University of Calgary.
Cardiol J. 2014;21(6):637-42. doi: 10.5603/CJ.2014.0096.
Vasovagal syncope can persist for decades and recur sporadically but many patients appear to improve after being seen in specialty clinics. The absence of specific and proven effective therapy raises the possibility that this might be due to regression to the mean or to a placebo effect. However, analysis using the Poisson distribution indicates the extreme unlikeliness that regression to the mean is the explanation. A main cause of the placebo effect is expectancy. Subject expectancy is the influence of the subject's anticipation of benefit on outcomes, and observer expectancy is the influence of investigator or physician attitudes and behavior on subject response. Ample data support the role of expectancy in outcomes of syncope patients. Moreover, expectancy can vary depending on the type of ineffective intervention. Interestingly, studies in which patients are blinded but the investigator is not show similar patient benefits compared with completely open label studies consistent with a strong observer expectancy effect due to physician-subject interaction. These results suggest the paramount importance of properly conducted randomized clinical trials in assessing biomedical interventions, and also illuminate the powerful potential of studies aimed at enhancing the expectancy effect on patient outcome.
血管迷走性晕厥可持续数十年且偶有复发，但许多患者在专科门诊就诊后病情似乎有所改善。由于缺乏特异性且经证实有效的治疗方法，这可能是由于均值回归或安慰剂效应。然而，使用泊松分布进行的分析表明均值回归作为解释的可能性极小。安慰剂效应的一个主要原因是期望。受试者期望是受试者对获益的预期对结果的影响，而观察者期望是研究者或医生的态度及行为对受试者反应的影响。大量数据支持期望在晕厥患者结果中的作用。此外，期望可能因无效干预的类型而异。有趣的是，与完全开放标签研究相比，患者被设盲但研究者未被设盲的研究显示出相似的患者获益，这与医生 - 受试者互动产生的强烈观察者期望效应一致。这些结果表明在评估生物医学干预措施时正确进行随机临床试验至关重要，同时也揭示了旨在增强期望效应以改善患者结局的研究的巨大潜力。
