Table 2.

Outcome comparisons between antisepsis and control sides.

	Antisepsis	Control	p-value3
Per patient comparison between sides
Primary endpoint
Drain bulb fluid colonization at POD 6-101	9.9% (10/101)	20.8% (21/101)	0.02
Secondary endpoints
Drain tubing colonization at removal	0% (0/97)	6.2% (6/97)	0.03
Drain bulb fluid colonization at removal2	19.4% (14/72)	38.9% (28/72)	0.003
Surgical site infection within 30 days	0	3.8% (4/104)	0.13
Surgical site infection within 1 year	2.9% (3/104)	5.8% (6/104)	0.45

	Antisepsis	Control
Per drain analysis			p-value4
Primary endpoint			Unadjusted	Adjusted5
Drain bulb fluid colonization at POD6-101	7.0% (11/157)	15.6% (25/160)	0.02	0.02
Secondary endpoints
Drain tubing colonization at removal	0% (0/151)	3.9% (6/154)	0.0046	N/A
Drain bulb fluid colonization at removal2	16.5% (14/85)	37.5% (33/88)	0.003	0.003

¹POD6-10 was the per protocol timeframe for the approximately 1 week culture; although 94% of visits occurred within this protocol range, the actual visit dates ranged from POD4-11.

²Reported here only in those where drain removal was later than primary endpoint collection.

³P-value from McNemar's test for paired proportions or the exact sign test.

⁴P-value from generalized linear mixed effects model accounting for correlation among multiple drains from the same patient.

⁵Adjusted for side- and drain-specific variables: indication (cancer or prophylaxis), operation (mastectomy only, mastectomy+SLNB, mastectomy+ALND), and drain duration.

⁶Due to zero events in the antisepsis arm for this endpoint, p-value was derived from likelihood-ratio test comparing the intercept only model to the model with intercept and treatment side included.