Parienti 2002.

Methods	Cluster‐randomised controlled equivalence trial Generation of random number sequence: random number tables Allocation concealment: no details given Blinding: discussed but only conducted during postdischarge follow‐up A priori sample calculations: yes Antisepsis protocol: yes Withdrawals: 51 patients lost during follow‐up Intention‐to‐treat analysis: yes Clear inclusion or exclusion criteria: yes
Participants	Surgical teams within 6 hospitals were randomised. 4387 patients undergoing clean and clean‐contaminated surgery were included in the study. Baseline comparability: details of surgical procedures, duration of surgery, patients' ASA classifications
Interventions	Group 1 ‐ 5 min scrub using either 4% povidone iodine or 4% chlorhexidine gluconate Group 2 ‐ 5 min handrub with alcohol solution containing 75% propanol‐1, propanol ‐2 with mecetronium ethylsulphate
Outcomes	Outcome measure: SSIs in patients at 30 d using CDC definition Method of testing: observation by surgeon or infectious disease specialist, case note review, telephone interview Timing of testing: 30 d follow‐up
Notes	Unclear if clustering is adjusted for in the analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Each participating surgical service was assigned a 2‐digit random number by using a random number table. Surgical services corresponding to the 3 higher numbers were assigned to hand‐rubbing with AAS and the remaining 3 services were assigned to traditional hand‐scrubbing". Comment: adequate evidence of random sequence generation
Allocation concealment (selection bias)	Unclear risk	Quote: "Each participating surgical service was assigned a 2‐digit random number by using a random number table. Surgical services corresponding to the 3 higher numbers were assigned to handrubbing with AAS and the remaining 3 services were assigned to traditional hand‐scrubbing" Comment: no evidence of allocation concealment
Blinding (performance bias and detection bias) All outcomes ‐ Blinding participants	High risk	Quote: "[O]bservers of the clinical outcome could not be blinded to the hand antisepsis protocol." The study also mentions that "compliance observers did not belong to the operating department team but were usually present in the surgical suite. To avoid a Hawthorne effect the surgical teams were not informed of the timing of the evaluations". Comment: Although the effect of blinding has been considered, in the comparison of different scrubbing protocols it would be difficult to blind the participant or personnel. The risk of bias is still high in this instance, however.
Blinding (performance bias and detection bias) All outcomes ‐ Blinding care givers	High risk	Quote: "[O]bservers of the clinical outcome could not be blinded to the hand antisepsis protocol." The study also mentions that "compliance observers did not belong to the operating department team but were usually present in the surgical suite. To avoid a Hawthorne effect the surgical teams were not informed of the timing of the evaluations". Comment: Although the effect of blinding has been considered, in the comparison of different scrubbing protocols it would be difficult to blind the participant or personnel. The risk of bias is still high in this instance, however.
Blinding (performance bias and detection bias) All outcomes ‐ Blinding outcome assessors	High risk	Surgical site infection outcome Quote: "According to CDC guidelines, all SSIs had to be confirmed by the surgeon or the physician in charge on the patient. Thus, observers of the clinical outcome could not be blinded to the hand antisepsis protocol" Comment: As the surgeon was the participant in this case. it is clear that this could constitute a high risk of bias. Tolerance and compliance outcome Quote: "[T]he surgical personnel (77 subjects) were asked to estimate the effect of the 2 protocols on their skin. We used 2 10 cm visual analogue scales, at month 0 and after 3 crossovers; 0 cm representing absence of an tolerance problem and 10 cm representing maximal dryness with chapped hands and desquamation or maximal irritation with erythema, burning sensation, and abrasion." Comment: The surgeon was the (unblinded) participant who reported the variables, so the results may be affected by performance bias.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "During the study period . . . 4823 consecutive patients underwent surgery. Among these, 385 patients underwent contaminated or dirty‐contaminated surgery, and 51 were lost to follow up at 30 days (17 in the hand‐rubbing group). The remaining 4387 patients (68.5% of whom underwent clean surgery) were considered for analysis". Comment: As the sample size is large, the numbers lost to follow‐up are not significant enough to warrant a risk of attrition bias.
Selective reporting (reporting bias)	Low risk	Quote: "Thirty‐day surgical site infections rates were the primary end point; operating department teams' tolerance of and compliance with hand antisepsis were secondary end points". Comment: adequate evidence in the results that these endpoints were accounted for comprehensively
Other bias	Unclear risk	This appears to be a clustered cross‐over study; it does not seem that clustering was taken into account in the analysis.