Controlling the controls: what is negative pressure wound therapy compared to in clinical trials?

Surgical site infections (SSIs) are common following colorectal operations. Clinical trials suggest that closed incision negative pressure wound therapy (ciNPWT) may reduce SSIs compared to a 'standard of care' group. However, wound management in the standard of care group may vary. The aim of this review was to assess the control arms in trials of ciNPWT for potential confounding variables that could influence the rates of SSI and therefore the trial outcomes.

A mapping review of the PubMed database was undertaken in the English language for randomized controlled trials that assessed, in closed surgical wounds, the use of ciNPWT compared to standard of care with SSI as an outcome. Data regarding wound care to assess potential confounding factors that may influence SSI rates were compared between the ciNPWT and standard of care groups. Included were the method of wound closure, control dressing type, frequency of dressing changes and postoperative wound care (washing).

Twenty-seven trials were included in the mapping review. There was heterogeneity in ciNPWT duration. There was little control in the comparator standard of care groups with a variety of wound closure techniques and different control dressings used. Overall standard of care dressings were changed more frequently than the ciNPWT dressing and there was no control over wound care or washing. No standard for 'standard of care' was apparent.

In randomized trials assessing the intervention of ciNPWT compared to standard of care there was considerable heterogeneity in the comparator groups and no standard of care was apparent. Heterogeneity in dressing protocols for standard of care groups could introduce potential confounders impacting SSI rates. There is a need to standardize care in ciNPWT trials to assess potential meaningful differences in SSI prevention.