Summary of findings 5. Basic wound contact dressing compared with hydrocolloid dressing.

Basic wound contact dressing compared with hydrocolloid dressing
Patient or population: surgical wounds healing by primary intention Setting: postsurgical Intervention: hydrocolloid dressing Comparison: basic wound contact dressing
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	№ of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with basic wound contact	Risk with hydrocolloid dressing
SSI Clean surgery Assessment method: CDC definition of SSI Follow‐up: mean 28 days Other surgery Assessment method: various clinical measures Follow‐up: 83 days but unclear for one of the RCTs	CLEAN SURGERY
	25 per 1000	22 per 1000 (7 to 69)**	RR 0.91 (0.30 to 2.78)	510 (1 RCT)** **One further trial reported no SSI events and was not included in this presentation of data as it was a split‐site study. One further RCT did not report SSI data.	⊕⊝⊝⊝ VERY LOW 1 2	It is uncertain if hydrocolloid dressings increase or reduce the risk of SSI compared with use of basic wound contact dressings following clean surgery, as the certainty of the evidence has been assessed as very low.
	Risk difference: 3 fewer SSIs per 1000 with hydrocolloid dressings (17 fewer to 44 more)
	OTHER SURGERY (WITH POTENTIAL FOR CONTAMINATION)
	80 per 1000	46 per 1000 (18 to 120)	RR 0.57 (0.22 to 1.51)	268 (3 RCTs)	⊕⊝⊝⊝ VERY LOW 3, 4	It is uncertain if hydrocolloid dressings increase or reduce the risk of SSI compared with basic wound contact dressings following potentially contaminated surgery, as the certainty of the evidence has been assessed as very low.
	Risk difference: 34 fewer SSIs per 1000 with hydrocolloid dressings (62 fewer to 41 more)
Scarring Clean surgery Assessment method: participants assessed different aspects of scarring as either: excellent, good or fair Follow‐up: 4 weeks potentially contaminated surgery Assessment method:measurement of scar width (mm) Follow‐up: 3 months	CLEAN SURGERY
	Not estimable	Not estimable	22/28 (79%) participants reporting on the hydrocolloid dressing rated their scar evenness as excellent compared with 14/28 (50%) reporting on the basic wound contact dressing. P value reported by study authors as 0.008. 22/28 (79%) participants reporting on the hydrocolloid dressing rated their scar colour as excellent compared with 13/28 (46%) reporting on the basic wound contact dressing. P value reported by study authors as 0.004. 21/28 (75%) participants reporting on the hydrocolloid dressing rated their scar suppleness as excellent compared with 15/28 (54%) reporting on the basic wound contact dressing. P value reported by study authors as 0.003.	28 (1 RCT)	⊕⊕⊝⊝ LOW 5	Hydrocolloid dressings may lead to some improvement in cosmetic appearance of scars compared with basic wound contact dressings following clean surgery.
	Potentially contaminated surgery
	The mean scar width was 2.3 mm	Mean difference 0.1 mm lower (0.91 lower to 0.7 higher)	n/a	134 (1 RCT)** **One other study reported scar width, but reported no standard deviation or related measure.	⊕⊕⊝⊝ LOW 6	Hydrocolloid dressings may lead to little or no improvement in cosmetic appearance of scars compared with basic wound contact dressings.
Acceptability of dressing to participant Clean surgery Assessment method: participants rated whether they were dissatisfied with the dressing Follow‐up: 4 weeks Unclear for other surgery	CLEAN SURGERY
	189 per 1000 (dissatisfied)	280 per 1000 (203 to 388)	RR 1.48 (1.07 to 2.05)	510 (1 RCT)	⊕⊕⊝⊝ LOW 7 8	Hydrocolloid dressings may lead to more dressing dissatisfaction compared with basic wound contact dressings following clean surgery.
	Risk difference: 91 more dissatisfied per 1000 with hydrocolloid dressings (13 more to 199 more)
	POTENTIALLY CONTAMINATED SURGERY
	Not estimable	Not estimable	Not estimable	n/a	n/a	Outcome not measured or reported for this comparison.
Ease of dressing removal Clean surgery Assessment method: questions regarding dressing removal Follow‐up: mean 4 days No details for potentially contaminated surgery Unclear for potentially contaminated surgery	CLEAN SURGERY
	Not estimable	Not estimable	Two studies reported ease of removal. One trial was a split‐site study. Data were not pooled because of this and other inconsistencies. One study reported 5/84 (6%) of respondents classified basic wound contact dressings as difficult to remove, compared with 13/61 (21%) in the hydrocolloid group. The second study reported at 3 days postoperatively that 22/28 (79%) participants reporting on the hydrocolloid dressing noted that the dressing was easy to remove compared with 18/28 (64%) reporting on the basic wound contact dressing.	173 (2 RCTs)	⊕⊝⊝⊝ VERY LOW 9 10 11	It is uncertain whether there are differences between hydrocolloid dressings and basic wound contact dressings in terms of ease of removal following clean surgery, as the certainty of the evidence has been assessed as very low.
	POTENTIALLY CONTAMINATED SURGERY
	Not estimable	Not estimable	Not estimable	n/a	n/a	Outcome not measured or reported for this comparison.
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CDC: Centers for Disease Control and Prevention; CI: Confidence interval; n/a: not applicable; OIS: optimal information size; RCT: randomised controlled trial; RR: risk ratio; SSI: surgical site infection
GRADE Working Group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty: we are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low certainty: our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low certainty: we have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

¹ Study at high risk of bias for outcome assessment. Downgraded once for risk of bias for study limitations.

² Studies were small with low numbers of SSI events: the OIS was not met. The 95% CIs around the estimate are wide ranging from a 70% reduction in risk of SSI in the hydrocolloid group to a 178% increase. Downgraded twice for imprecision.

³Two studies (weighted 65% in the meta‐analysis) were at high risk of bias. Downgraded twice for risk of bias for study limitations.

⁴ Studies were small with low numbers of SSI events: the OIS was not met. 95% CIs that ranged from a 78% reduction in SSI risk in the hydrocolloid group to a 51% increase. Downgraded twice for imprecision.

⁵This was a split‐site study with half of a wound treated with one dressing and half with the other. The authors assessed scar colour, texture and colour on a 3‐point scale; the lack of independence seems to have been considered by authors, but they only present P values (favouring the hydrocolloid dressing). We have not reproduced the analysis, so given the lack of precision data and the small number of wounds in the study, have downgraded twice for imprecision.

⁶ Whilst the study resulted in precise estimates, data are available from just one study with a relatively small number of participants. Further data from more participants would add to certainty. Downgraded once for imprecision. Scarring can also be assessed in a number of ways with width being just one measure, use of a validated tool would be a more useful for decision making. Downgraded once for indirectness.

⁷The study had 95% CIs that ranged from a 7% increase risk of dissatisfaction in the hydrocolloid group to 105% increase risk, downgraded once for imprecision.

⁸ Risk of bias as unclear for sequence generation and allocation concealment. Downgraded once for study limitations.

⁹One study was classed at high risk of bias in two domains. Downgraded twice in limitations.

¹⁰ Studies had small sample sizes. Downgraded once for imprecision.

¹¹Results were inconsistent ‐ the reason for inconsistency is not clear. Downgraded once for inconsistency.