Table 2.

Clinical outcomes for intention to treat population with missing data on primary outcome (28 women) assumed to be no surgical site infection (SSI), conservatively favouring standard care^*. Values are numbers (percentages) unless stated otherwise

Clinical outcomes	All (n=2035)	Closed incision NPWT (n=1017)	Standard dressing (n=1018)	Relative risk (95% CI)	P value†
All SSI types	174 (8.6)	75 (7.4)	99 (9.7)	0.76 (0.57 to 1.01)	0.06
Superficial	163/174 (94)	70/75 (93)	93/99 (94)	0.75 (0.56 to 1.02)	0.72
Deep incision	10/174 (5.7)	4/75 (5)	6/99 (6)	0.67 (0.19 to 2.36)	0.72
Organ/space	1/174 (0.6)	1/75 (1)	0/99 (0)	-	0.50
Complications	247 (12.1)	123 (12.1)	124 (12.2)	0.99 (0.79 to 1.25)	0.95
Bleeding	30 (1.5)	14 (1.4)	16 (1.6)	0.88 (0.43 to 1.79)	0.72
Dehiscence	211 (10.4)	108 (10.6)	103 (10.1)	1.05 (0.81 to 1.36)	0.71
Haematoma	17 (0.8)	11 (1.1)	6 (0.6)	1.84 (0.68 to 4.94)	0.22
Seroma	53 (2.6)	27 (2.7)	26 (2.6)	1.04 (0.61 to 1.77)	0.89
Median (IQR) HLOS, days (n=2019)‡	3.0 (2.0-4.0)	3 (2.0-4.0)	3 (2.0-4.0)	-	0.32
Readmissions‡	36 (1.8)	23 (2.3)	13 (1.3)	1.76 (0.90 to 3.46)	0.09
Pain‡ §	32 (1.6)	21 (2.1)	11 (1.1)	1.90 (0.92 to 3.93)	0.07
Reoperations‡ ¶	9 (0.4)	4 (0.4)	5 (0.5)	0.80 (0.22 to 2.96)	0.75

HLOS=hospital length of stay; IQR=interquartile range; NPWT=negative pressure wound therapy.

^*Worst case analysis based on effect estimate; 28 women missing primary outcome data (12 lost to follow-up; 16 withdrawn) assumed not to have SSI (favouring standard dressing as this arm has higher levels of missing data).

^†Using χ² test, Fisher’s exact test, or Mann-Whitney U test.

^‡Data not available for randomised patients withdrawn from study.

^§Pain associated with surgical wound requiring readmission measured as binary variable (yes/no).

^¶5 participants had reoperations for wound complications before hospital discharge.