Ko 2009.

Study characteristics
Methods	Study design: prospective randomised controlled trial Randomisation technique: web‐based Allocation concealment: adequate Inclusion criteria: well explained Exclusion criteria: well explained Lost to follow‐up: adequate Baseline variables: matching between both limbs of the trial Intention‐to‐treat analysis: reported Sample size calculations (power of the study): reported
Participants	Country: South Korea Number of participants: FG: 50 and NFG: 50 Mean age (years): FG 48.5 ± 8.7; NFG 47.9 ± 7.7
Interventions	FG: Greemplast Kit® was applied under skin flaps following breast and axillary surgery Types of surgical intervention: lumpectomy Confounding interventions: compression for 5 days
Outcomes	Primary: incidence of seroma Secondary: mean volume of seroma postoperative complications wound infection total volume of seroma mean number of drainage days
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Web based
Allocation concealment (selection bias)	Low risk	Adequate
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Adequate
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Adequate
Incomplete outcome data (attrition bias) All outcomes	High risk	Not reported
Selective reporting (reporting bias)	Low risk	No
Other bias	Low risk	Inclusion, exclusion criteria, ethics approval and conflict of interest declaration was adequately reported