Wheelock 1997.

Methods	Randomised cross‐over trial Generation of random number sequence: no details given Allocation concealment: no details given Blinding: no details given (dermal tolerance) A priori sample calculations: yes Antisepsis protocol: yes Withdrawals: no details given Intention‐to‐treat analysis: no Clear inclusion or exclusion criteria: no
Participants	25 operating theatre nurses and surgical technologists Baseline comparability: age, gender, hand size, role, length of perioperative experience
Interventions	Group 1 ‐ 3 min surgical scrub using either 4% chlorhexidine, 2% chlorhexidine or parachlorometaxylenol Group 2 ‐ 2 min surgical scrub using either 4% chlorhexidine, 2%chlorhexidine or parachlorometaxylenol
Outcomes	Outcome measure: CFUs on participants' hands Method of testing: glove juice method Timing of testing: 1 h after antisepsis
Notes	Participants did not take part in any surgical procedures.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote "We randomly assigned subjects to one of two study groups (i.e., two‐minute, three‐minute surgical hand scrub times)." Comment: no indication as whether a truly randomised sequence was generated
Allocation concealment (selection bias)	Unclear risk	Quote "We randomly assigned subjects to one of two study groups (i.e., two‐minute, three‐minute surgical hand scrub times)." Comment: no indication as to whether allocation was concealed to the participants or personnel. The study was a cross‐over trial, therefore all the participants were likely to have undertaken the same interventions; however, the role of bias is unclear in this case.
Blinding (performance bias and detection bias) All outcomes ‐ Blinding participants	High risk	No direct quotes given, but no mention as to whether the subjects or the personnel were blinded to the intervention. It is very likely that the personnel were not blinded as they would be able to calculate the time spent handwashing.
Blinding (performance bias and detection bias) All outcomes ‐ Blinding care givers	High risk	No direct quotes given, but no mention as to whether the subjects or the personnel were blinded to the intervention. It is very likely that the personnel were not blinded as they would be able to calculate the time spent handwashing.
Blinding (performance bias and detection bias) All outcomes ‐ Blinding outcome assessors	High risk	No direct quotes given, but investigators were responsible for measurement of time and for preparation of solution for bacterial culture, as well as the sampling and measurement of log CFU counts. Although this is an objective measure, it is reasonable to suggest that as the investigators were not blinded to the intervention then the risk of bias here could be considered as high.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Each subject was able to complete both surgical hand scrub trials, which resulted in 300 agar plates for incubation and enumeration." Comment: adequate evidence of no loss to follow‐up
Selective reporting (reporting bias)	Low risk	The main outcome variable was the log counts of bacterial colonies found on participants' hands after washing their hands for a specified time. This was fully represented in table format in the results section.
Other bias	Unclear risk	Although the trial had a cross‐over design. it did not appear that this was reflected in the analysis

AAS: aqueous alcohol solution;ABWA: alcohol‐based water‐aided; ASA: American Society of Anesthesiologists; CDC: Centers for Disease Control; CFU: colony forming units; CHG: chlorhexidine gluconate; C/S: culture and sensitivity PVI: povidone iodine; SSI: surgical site infection; v/v: volume/volume per cent.