Ko 1992.

Study characteristics
Methods	QRCT
Participants	1980 adults having cardiopulmonary bypass surgery in the USA between July 1987 and June 1989
Interventions	Group 1: hair removal with razor (n = 990) Group 2: hair removal with a clipper (n = 990) Product details: no details are given for the razor, the clippers were Remington, 3M. Timing of hair removal: the night before surgery for elective cases, and immediately before surgery for emergency cases. Hair removed by: not specified. Venue for hair removal: not reported for elective surgery, the operating table for emergency cases.
Outcomes	Outcome: suppurative mediastinitis (the authors use this term interchangeably with sternal wound infection). Definition included; pain, fever, erythema, purulent drainage, sternal instability, tenderness, and leukocytosis. Needle aspiration sometimes used to assist diagnosis. Wounds were examined by the surgical team at least twice a day. 1 infection was diagnosed at the 30‐day postoperative follow‐up visit. No other details are given regarding assessment.
Notes	Participants were also randomised to receive either saline or povidone iodine intraoperative irrigation. No funding sources mentioned. No details of conflict of interest.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "according to the last two digits of their hospital numbers" Comment: inadequate randomisation technique.
Allocation concealment (selection bias)	High risk	Quote: "according to the last two digits of their hospital numbers" Comment: care provider could predict allocation by reference to hospital number.
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	Wounds were examined by the surgical team twice a day. Comment: unclear whether assessors were blinded to intervention allocation.
Incomplete outcome data (attrition bias) ITT analysis undertaken	Unclear risk	Not reported. Comment: no discussion of whether participants were analysed in groups to which they had been allocated.
Incomplete outcome data (attrition bias) Drop out rate acceptable	Unclear risk	Not reported. Comment: insufficient details to permit a judgement.
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.