Critical appraisal:Veenhof AA, Sietses C, von Blomberg BM, van Hoogstraten IM, vd Pas MH, Meijerink WJ, et al 2011 3

Risk of bias assessment: Randomised Controlled Trial (Cochrane risk of bias tool)

Random sequence generation

Describe the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

Patients were then randomly assigned in a

2:1 ratio to laparoscopic surgery or open surgery in
accordance with a list of randomisation numbers and
treatment allocation. This list was com puter generated by
the trial statistician

What was the risk of bias from the random sequence generation?

Low

Allocation concealment

Describe the method used to conceal the allocation sequence in sufficient detail to determine whether intervention allocations could have been foreseen in advance of or during, enrolment.

After eligibility had been established and patients provided

written informed consent, the local investigator registered
patients on the trial’s website to ensure allocation
concealment.

What was the risk of bias from the allocation concealment?

Unclear

Blinding

Describe all measures used, if any, to blind outcome assessors from knowledge of which intervention a participant received. Provide any information relating to whether the intended blinding was effective.

Blinding not described

What was the risk of bias from the blinding of participants and personnel and outcome assessors?

Unclear

Incomplete outcome data

Describe the completeness of outcome data for each main outcome, including attrition and exlusions from the analysis. State whether attrition and exclusions were reported, the numbers in each intervention group (compared with total randomized participants), reasons for attrition/exclusions where reported, and any re-inclusions in analyses performed by the review authors.

All relevant participant data presented (n=40).

What was the risk of bias from incomplete outcome data?

Low