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. 2014 May 21;348:g3253.
doi: 10.1136/bmj.g3253.

Use of Placebo Controls in the Evaluation of Surgery: Systematic Review

Free PMC article

Use of Placebo Controls in the Evaluation of Surgery: Systematic Review

Karolina Wartolowska et al. BMJ. .
Free PMC article


Objective: To investigate whether placebo controls should be used in the evaluation of surgical interventions.

Design: Systematic review.

Data sources: We searched Medline, Embase, and the Cochrane Controlled Trials Register from their inception to November 2013.

Study selection: Randomised clinical trials comparing any surgical intervention with placebo. Surgery was defined as any procedure that both changes the anatomy and requires a skin incision or use of endoscopic techniques.

Data extraction: Three reviewers (KW, BJFD, IR) independently identified the relevant trials and extracted data on study details, outcomes, and harms from included studies.

Results: In 39 out of 53 (74%) trials there was improvement in the placebo arm and in 27 (51%) trials the effect of placebo did not differ from that of surgery. In 26 (49%) trials, surgery was superior to placebo but the magnitude of the effect of the surgical intervention over that of the placebo was generally small. Serious adverse events were reported in the placebo arm in 18 trials (34%) and in the surgical arm in 22 trials (41.5%); in four trials authors did not specify in which arm the events occurred. However, in many studies adverse events were unrelated to the intervention or associated with the severity of the condition. The existing placebo controlled trials investigated only less invasive procedures that did not involve laparotomy, thoracotomy, craniotomy, or extensive tissue dissection.

Conclusions: Placebo controlled trial is a powerful, feasible way of showing the efficacy of surgical procedures. The risks of adverse effects associated with the placebo are small. In half of the studies, the results provide evidence against continued use of the investigated surgical procedures. Without well designed placebo controlled trials of surgery, ineffective treatment may continue unchallenged.

Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare: the authors are involved in a placebo controlled surgical trial on shoulder pain (NCT01623011); no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.


Fig 1 Flow chart of study identification, listing first reason for exclusion during review process
Fig 2 Forest plot of studies with binary outcome measures showing magnitude of effect (odds ratios) in active group compared with placebo group. GERD-HRQL=gastro-oesophageal reflux disease health related quality of life
Fig 3 Forest plot of studies with continuous outcome measures showing magnitude of effect (effect sizes) in active group compared with placebo group. Outcome values in Stone and colleagues trial were not normally distributed; therefore, the effect size does not represent the true difference. WOMAC=Western Ontario and McMaster Universities arthritis index; KSPS=knee specific pain scale; QoL=quality of life; BMI=body mass index; GERD-HRQL=gastro-oesophageal reflux disease health related quality of life; NRS=numerical rating scale; RF=radiofrequency; SF-36=short form (36) health survey; CSF=cerebrospinal fluid; UPDRS=unified Parkinson’s disease rating scale; EQ5D=EuroQol Group health questionnaire; RMS=modified Roland-Morris scale; ODI=Oswestry disability index; ESS=Epworth sleepiness scale; MDRS=Mattis dementia rating scale

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