de Laat 2011.

Study characteristics
Methods	2‐arm RCT Multi‐centred, conducted in hospital settings in the Netherlands Duration of follow‐up was a maximum of 6 weeks
Participants	24 participants (with a total of 28 wounds). 12 of these participants had pressure ulcers. Data were extracted and presented for the pressure ulcer subgroup only. Inclusion criteria listed: patients ≥ 18 years who were admitted to the study hospitals with difficult‐to‐heal surgical wounds, or paraplegic and tetraplegic patients with pressure ulcers grade IV according to the European Pressure Ulcer Advisory Panel grading system Exclusion criteria listed: patients with bleeding disorders; thrombolytic treatment; fistulas to organs or body cavities; malignant disease; untreated osteomyelitis; life expectancy of < 1 year; radiation or chemical exposure; pregnant or lactating women; people unable to comply with 1 of the interventions or who had been treated with 1 of the study treatments in the past 30 days
Interventions	Group A: NPWT (VAC system, vacuum‐assisted closure; KCI, San Antonio, TX, USA; n = 6, 7 pressure ulcers). "Devices were used in accordance with the manufacturer's guidance. The foam dressings and the TRAC Pad were changed 3 times a week (Monday morning, and Wednesday and Friday in the afternoon). The fluid connection system was changed at least once a week. Negative pressure mode of 125 mm Hg." Group B: conventional dressing therapy (n = 6, 9 pressure ulcers) with a sodium hypochlorite 0.25% solution. "This wet‐to‐moist dressing was changed 2 to 3 times a day, depending on the wound debris. The sodium hypochlorite solution was prepared by one hospital pharmacist." Co‐intervention: wound debridement took place when considered clinically necessary before the start of the therapy and during treatment. Participants received (medical) care as needed
Outcomes	Primary outcomes: adverse events Secondary outcomes: change in wound size
Notes	Some participants had more than one ulcer, so there was potential for unit of analysis issues although this is not clear from the report Funding source: the surgical department of Nijmegen University Medical Centre
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "A prospective stratified randomised controlled trial was carried out …" Comment: method of generating of random schedule is not reported
Allocation concealment (selection bias)	Unclear risk	Quote: "Patients in the difficult‐to‐heal surgical wounds group or the spinal cord injury patients with pressure ulcer group, were both allocated randomly to either the topical negative pressure group or the sodium hypochlorite group by using sealed envelopes." Comment: whilst sealed envelopes were used to conceal allocation it is not clear whether these were numbered to ensure sequential opening, or opened by an independent person
Blinding of outcome assessment (detection bias) All outcomes	High risk	The median treatment time to 50% reduction of wound volume Quote: "Because of the striking foam imprints in the wound of patients with topical negative pressure therapy blinding was not possible." Comment: not blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: flow chart shows that all participant and all wounds data were included in analysis; the presentation of the data and methods outlined show that an ITT analysis was done considering all randomised participants
Selective reporting (reporting bias)	Low risk	Comment: based on paper only, protocol not obtained
Other bias	Unclear risk	Comment: it was not clear whether there were unit of analyses issues