Nordkam 2005.

Methods	Study design: randomised controlled trial. Object of randomisation: patients.
Participants	Netherlands. Surgeons and assistants performing laparotomies, abdominal closure: fascia. Number studied: 200 procedures, 400 operators and 406 pairs of gloves. Intervention group n = 200 surgeon‐operations. Control group n = 100 surgeon‐operations. Gloves changed before skin closure.
Interventions	Use of blunt‐tapered needles. Control group used sharp needles.
Outcomes	Outcome: Number of procedures with one or more glove perforations per total number of procedures. Outcome calculated: holes in gloves per operator per operation Perforation detection: The gloves were filled with water and perforations were noted as jets of water. Secondary outcome: Ease of use of the needles.
Notes	We received additional information from the authors
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	randomisation by envelope; authors wrote that randomisation was based on a computer generated random number
Allocation concealment (selection bias)	Low risk	"just before closure of the fascia"; randomisation by envelope
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	team was aware of type of needle used; blinding to type of needle is impossible for surgeons
Blinding of outcome assessment (detection bias) All outcomes	Low risk	not reported; authors wrote that observer was blind to which needle was used
Incomplete outcome data (attrition bias) All outcomes	Low risk	all gloves retrieved
Selective reporting (reporting bias)	Low risk	all outcomes reported