Erkens 1992.

Study characteristics
Methods	This study was carried out in a primary care setting, and it was open. Intention‐to‐treat analysis was carried out. This study was conducted in Netherlands.
Participants	93 participants were recruited: 18 dropped out. Inclusion criteria of the trial Adults and children Ordinary warts Warts on the hands
Interventions	Monthly cotton wool bud cryotherapy versus Bimonthly Histofreezer Treatment continued for up to 2.5 months.
Outcomes	Outcomes of the trial Cure at 2.5 months
Notes	Cryotherapy was applied with a cotton tip.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	This was described as randomised; no details were given.
Allocation concealment (selection bias)	Unclear risk	This was adequate; sealed envelopes were used. It was unclear if they were sequentially numbered and opaque.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote (page 193): "Neither the doctor nor the patient knew beforehand which treatment was to be used." Comment: This was blinded.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No details were given.
Incomplete outcome data (attrition bias) All outcomes	Low risk	17/93 participants withdrew (7/17 in the cryotherapy group and 10/17 in the Histofreezer group): The reason given was that they 'did not comply fully with protocol'. Comment: Reasons for dropouts were given; there was equal distribution between the groups.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.