Balthazar 1983.

Study characteristics
Methods	RCT
Participants	200 people having elective inguinal hernia repair in the USA between 1978 and 1981
Interventions	Group 1: preoperative hair removal with a razor (n = 100) Group 2: preoperative hair removal with clippers (n = 100) Product details: razors were "safety razors" with a wet shave which were washed between cases, the clippers were "ordinary barbers electric clippers". Timing of hair removal: immediately before surgery. Hair removed by: not specified. Venue for hair removal: not reported.
Outcomes	Primary outcome: wound infection defined as "discharge of purulent exudate", assessed by infection control nurse daily for 5 days postoperatively and by unspecified practitioners at 2 weeks postoperatively. Secondary outcome: adequacy of hair removal, skin trauma judged by attending surgeon.
Notes	All recruited participants were male; no statistical test of significance. No funding sources mentioned. No details of conflict of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Patients randomised using standard table of random numbers" Comment: done.
Allocation concealment (selection bias)	Unclear risk	Not reported. Comment: not clear whether the person responsible for allocation to groups would have been able to predict to which group a potential participant would be allocated.
Blinding (performance bias and detection bias) Care providers blinded	Unclear risk	Not reported. Comment: unclear whether care providers were blinded to intervention allocation.
Blinding (performance bias and detection bias) Participants blinded	High risk	Not reported. Comment: participants would have been aware of hair removal method.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported. Comment: unclear whether assessors were blinded to intervention allocation.
Incomplete outcome data (attrition bias) ITT analysis undertaken	Unclear risk	Not reported. Comment: no information provided regarding whether participants were analysed in the groups to which they had been allocated.
Incomplete outcome data (attrition bias) Drop out rate acceptable	Low risk	It appears that no participants dropped out from the study. Comment: 200 participants reported in the results section.
Selective reporting (reporting bias)	Low risk	Main outcomes reported. Comment: unlikely to be affected by reporting bias.
Other bias	Low risk	Comment: participant groups were equal or similar.