Levy 1988.

Methods	Single‐centre RCT (USA) Study period: not reported Setting: no clear description of the study setting except that the study was conducted on "patients undergoing coronary artery surgery".
Participants	'Patients and methods': "60 patients scheduled for coronary artery surgery were studied during right internal jugular vein cannulation for PA catheter insertion." Number of participants: 60 Number of catheters;60 Age: not reported Sex: not reported
Interventions	Comparison of 2 skin preparation regimes before insertion of CVC. Intervention A: 1 minute‐cleaning with 70% isopropyl alcohol followed by draping with a sterile non‐absorbent sheet with an iodophor‐impregnated adherent film placed over the aperture. Intervention B: povidone‐iodine swabs followed by draping with a sterile non‐absorbent sheet.
Outcomes	Catheter colonisation Bacterial contamination of surgical gloves Outcomes assessed at various points during in‐patient stay.
Notes	Funding source: not stated.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	'Patients and methods': "Patients were assigned randomly assigned to one of two groups." There was no further information, including on random sequence generation.
Allocation concealment (selection bias)	Unclear risk	There was no information in the paper to enable an assessment on whether random sequence generation was independent from allocation.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Although the authors did not explicitly say, blinding of the patient and personnel was highly unlikely because the 2 skin antisepsis regimes differed in the way of administration (1 using a liquid solution and an additional adherent film and the other using a swab without an adherent film).
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding for microbiological outcome assessment not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	Authors analysed all 60 participants initially enrolled and seemed to follow the intention‐to‐treat principle.
Selective reporting (reporting bias)	High risk	Authors reported both major outcomes named in the 'Methods', catheter colonisation and positive glove culture, in sufficient detail in the 'Results'. However, they did not include major patient‐related outcomes such as catheter‐related BSI, sepsis or mortality.
Other bias	Low risk	None identified