Leon 2016.

Methods	Study design: prospective, randomised, multicentre study Study grouping: parallel Ethics and informed consent: not reported Follow‐up period: not reported Sample size estimate: not reported ITT analysis: yes number randomised: 81 number analysed: 81 Funding: not reported Pre‐registration: not reported
Participants	Location: Spain Intervention group: n = 47control group: n = 34 Mean age (SD): not reported Inclusion criteria: patients undergoing open and programmed colorectal surgery Exclusion criteria: not stated
Interventions	Aim/s: to evaluate the benefits of negative pressure therapy to reduce surgical site infection rate in open colorectal surgery Group 1 (NPWT) intervention: NPWT Group 2 (control) intervention: usual dressing group Study date/s: not reported
Outcomes	SSI rate Validity of measure/s: not described Time points: a daily evaluation through hospitalisation and a 15‐ and 30‐day evaluation
Notes	Only the abstract was available.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Evidence for participants: not possible Comment: unlikely to affect outcomes Evidence for personnel: not possible Comment: unlikely to affect outcomes
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	All enrolled participants were accounted for in the analyses.
Selective reporting (reporting bias)	Unclear risk	Not stated
Other bias	Unclear risk	Abstract only