Tennenberg 1997.

Methods	Single‐centre RCT (USA)
Participants	Quote: "Patients eligible for the study were inpatients on the surgical, medical, and intensive care unit wards who were deemed by their physicians to require CVC placement for their care. To eliminate the potential contamination associated with CVCs placed over guidewires, only patients who required fresh‐stick CVC insertion in the subclavian, jugular, or femoral sites were eligible for study."
Interventions	C‐SS‐impregnated CVCs versus non‐impregnated CVCs
Outcomes	Catheter colonization, CRBSI and catheter‐related local infection
Notes	Sources of funding: industry (catheter manufacturer or distributor)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “….disparate allocations from a large master computer‐generated randomization list in blocks of 8 were used for these different patient locations and for the number of CVC lumens.”
Allocation concealment (selection bias)	Unclear risk	Quote: "Allocation was carried out using sealed envelope during randomization which occurred after informed consent."
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: “The study was not blinded because the physician became aware (by opening a sealed envelope) of the CVC type required after randomization.”
Blinding of outcome assessment (detection bias) Microbiological outcomes like catheter colonization	Unclear risk	There was no mention of whether the assessors of the microbiological outcomes were blinded to the status of the sample
Blinding of outcome assessment (detection bias) Clinical outcomes like CRBSI	High risk	Quote:“The study was not blinded because the physician became aware (by opening a sealed envelope) of the CVC type required after randomization.”
Incomplete outcome data (attrition bias) All outcomes	High risk	70/350 catheters (19.9%) were excluded from the analysis. It was unclear how many of the excluded catheters belonged to each group. The reasons for exclusion were as follows: "less than 48 hours of catheterization (34 patients), incomplete cultures (26 patients), ongoing sepsis from another source (3 patients), and other reasons (CVC not inserted, wrong CVC inserted, CVC misplaced, and CVC accidentally removed) (7 patients)." In view of the high rate of exclusion and relatively low event rates for the outcomes of CRBSI and catheter colonization, we felt that there was a high risk of attrition bias in this study
Selective reporting (reporting bias)	Low risk	All the outcomes specified in the Methods, including catheter colonization, CRBSI and catheter‐related local infections were reported in sufficient detail in the Results
Other bias	Low risk	None identified