Table 2.

Methods to blind patients, surgeons and outcome assessors in examples of RCTs in surgery

Trial	Interventions	Primary outcome	Type of outcome	Personnel blinded	Methods used for blinding
Raviele et al. 2004 [52]	Permanent pacing versus placebo for recurrent tilt-induced vasovagal syncope	Recurrence rate of syncope at 1 year assessed by patient diaries	PRO	Patients Surgeons Clinical staff	Pacemakers implanted into both treatment arms using the same method; a single person in each centre was responsible for the programming of the pacemaker to ON in active mode with rate drop response, or OFF in the inactive mode.
Sung et al. 2003 [53]	Endoscopic treatment versus irrigation alone for non-bleeding vessels or adherent clot in gastroduodenal ulceration	Recurrence of bleeding before discharge and at 30 days	Independent adjudication panel	Patients Clinical staff Outcome assessors	Intervention group underwent routine endoscopic treatment for bleeding ulcer including irrigation, suction, heater probe, or mini-snare. The control group received irrigation of ulcer base but no manipulation with heater probe, snare or suction; post-operative care by blinded clinical team; endoscopist not involved in post-operative care or outcome assessment; criteria for re-bleed pre-defined and assessed by blinded panel.
Moseley et al. 2002 [49]	Arthroscopic lavage and debridement versus arthroscopic lavage only versus sham procedure for osteoarthritis of the knee	Knee pain at 24 months assessed using Knee-Specific Pain Scale (developed for this trial)	PRO	Patients Nurses Clinical staff	Patients allocated to lavage and debridement or lavage only underwent general anaesthesia and endotracheal intubation. Patients in the control arm underwent short-acting intravenous sedation and opioid analgesia with spontaneously breathed oxygen-enriched air. Patients allocated to lavage and debridement received a standard arthroscopic procedure. Patients allocated to lavage only underwent an identical procedure except that no debridement was performed (unless an unstable meniscal tear was identified in which case this was excised). For patients in the control arm, the knee was prepped and draped as usual and the 1-cm incisions performed. No instrumentation was performed but the surgeon manipulated the knee as per arthroscopic debridement. Post-operative care was provided by blinded clinical staff according to a standardised pathway; the surgeon was not involved in post-operative care or outcome assessment.
Vitek et al. 2003 [54]	Pallidotomy versus medical therapy for Parkinson’s disease	Average change in unified Parkinson’s disease rating scale at 6 months	Assessor reported	Independent assessors	Two independent outcomes assessors blind to treatment allocation collected all outcome data; all patients wore hats to mask scars during baseline and follow-up outcomes collection; there was no contact between assessors and participants between follow-up appointments; assessors were not involved in the routine care of participants; patients were asked not to inform assessors of treatment allocation.
Quinn et al. 2002 [55]	Suturing versus conservative management of hand lacerations	Cosmetic appearance at 3 months	Assessor reported	Independent assessors	Assessment of wounds made photographically with no knowledge or contact with participant at 3 months after treatment by two independent doctors.
Gervaz et al. 2010 [56]	Laparoscopic versus open (lower midline) approach for sigmoid colectomy to treat diverticular disease	Composite pain assessed daily for 4 days; time to first flatus/bowel movement	PRO	Patients Nursing staff	Sterile, opaque dressing to cover entire lower abdomen for 4 days
Ezra et al. 2004 [57]	Vitrectomy alone versus vitrectomy plus autologous serum transfer versus conservative management for full thickness macular hole	Composite closure of macular hole and visual acuity (time point unclear)	Assessor reported	Independent assessors	Closure of hole accessed via digitalised photographs of fundoscopy and digitalised images of flourescein angiography. These assessments were made separately as vitrectomy is obvious on fundoscopy. This way partial blinding between the arms was maintained because serum transfer cannot be seen; blinded assessment by a separate assessor of visual acuity

PRO patient-reported outcome