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OBJECTIVES: To examine key methodological considerations for using a placebo intervention in randomized controlled trials (RCTs) evaluating invasive procedures, including surgery. STUDY DESIGN AND SETTING: RCTs comparing an invasive procedure with a placebo were included in this systematic review. Articles published from database inception to December 31, 2017, were retrieved from Ovid MEDLINE, Ovid EMBASE and CENTRAL electronic databases, by handsearching references and expert knowledge. Data on trial characteristics (clinical area, nature of invasive procedure, number of patients and centers) and key methodological (rationale for using placebos, minimization of risk, information provision, offering the treatment intervention to patients randomized to placebo, delivery of cointerventions, and intervention standardization and fidelity) were extracted and summarized descriptively. RESULTS: One hundred thirteen articles reporting 96 RCTs were identified. Most were conducted in gastrointestinal surgery (n = 40, 42%) and evaluated minimally invasive procedures (n = 44, 46%). Over two-thirds randomized fewer than 100 patients (n = 65, 68%) and a third were single center (n = 31, 32%). A third (n = 33, 34%) did not report a rationale for using a placebo. Most common strategies to minimize patient risk were operator skill (n = 22, 23%) and independent data monitoring (n = 28, 29%). Provision of patient information regarding placebo use was infrequently reported (n = 11, 11%). Treatment interventions were offered to patients randomized to placebo in 43 trials (45%). Cointerventions were inconsistently reported, but 64 trials (67%) stated that anesthesia was matched between groups. Attempts to standardize interventions and monitor their delivery were reported in n = 7, (7%) and n = 4, (4%) trials, respectively. CONCLUSION: Most placebo-controlled trials in surgery evaluate minor surgical procedures and currently there is inconsistent reporting of key trial methods. There is a need for guidance to optimize the transparency of trial reporting in this area.

Original publication




Journal article


J Clin Epidemiol

Publication Date





109 - 116


Invasive procedures, Methodology, Placebo surgery, Surgery, Systematic review