Prager 1984.

Methods	Single‐centre RCT (USA) Study period: not reported Setting: hospital departments of General Surgery (123), Medicine (20), Thoracic Surgery (19), Neurosurgery (8), Obstretrics and Gynaecology (3), Paediatrics (3) and others (3)
Participants	All hospital inpatients who required a CVC Number of participants: 159 adults, 3 children Number of catheters; 179 Age: not reported Sex: not reported
Interventions	Skin antisepsis applied daily after CVC insertion. Intervention A: povidone‐iodine for skin antisepsis Control: no skin antisepsis
Outcomes	Catheter colonisation "Catheter‐related septicaemia" (catheter‐related BSI) Outcomes assessed at various points during in‐patient stay.
Notes	Funding source: supported in part by the Purdue Frederick Company, Wilmington, Delaware.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	The exact method of sequence generated was not described. However, in the 'Methods', the authors stated that patients were randomised according to hospital registration number, suggesting that they used alternation, instead of true randomisation.
Allocation concealment (selection bias)	High risk	As above
Blinding of participants and personnel (performance bias) All outcomes	High risk	Although the authors did not explicitly say, it was unlikely that the participants and the care providers were blinded, as the study assessed skin antisepsis versus no skin antisepsis.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Blinding of microbiological outcome assessor not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	Although the authors did not describe any withdrawals, it appeared that all catheters that were initially enrolled were analysed in the originally assigned groups.
Selective reporting (reporting bias)	Low risk	Authors reported the major outcomes of catheter colonisation and catheter‐related BSI as stated in the 'Methods' in sufficient detail in the 'Results'. The authors also reported an additional outcome of skin erythema. However, this was reported as an overall percentage of patients with colonised catheters, not according to the allocated groups, and so it did not allow data extraction for meta‐analysis. Nevertheless, this did not affect our judgment on the overall risk of reporting bias in any major way.
Other bias	High risk	There was a unit of analysis issue in which the number of catheters analysed exceeded the number of participants by nearly 10%, and the outcomes were reported using catheters as the units.