Law 1987.

Methods	3‐arm RCT undertaken in the UK
Participants	People undergoing inguinal hernia repair or high saphenous ligation. 170 participants randomised. 4 participants lost to follow‐up, but unclear to which group(s) they belonged. No information provided regarding follow‐up.
Interventions	Group A (n = 59): gauze, removed on day 5, or changed if wound was discharging Group B (n = 54): film dressing (Opsite; Smith & Nephew), removed on day 5. Discharge aspirated through dressing, and new dressing applied, if necessary. Group C (n = 53): exposed wound (if discharge, covered with gauze for as long as necessary)
Outcomes	Primary review outcome: SSI (not defined) Secondary review outcome: cost (total dressing cost)
Notes	Trial outcome data: see Table 12 Follow‐up: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...were randomly allocated to one of three surgical dressing options". Comment: not enough detail provided to understand process.
Allocation concealment (selection bias)	Unclear risk	No details provided in the report.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	No mention of blinding in the trial report.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: trial notes that 4 participants were lost to follow‐up.
Selective reporting (reporting bias)	Unclear risk	Lack of data for certain outcomes such as preference, scarring and comfort.
Other bias	Unclear risk	No baseline data presented.