Vance 1986.

Study characteristics
Methods	This study was carried out in a secondary care setting, and it was multicentre. This study was blinded. Intention‐to‐treat analysis was not carried out. This study was conducted in the USA.
Participants	111 participants were recruited: 11 dropped out. Inclusion criteria of the trial Adults Ordinary or refractory warts not specified Warts on the feet only
Interventions	IFN‐alpha: high‐dose 10 millionU/ml versus Low‐dose 1 millionU/ml versus Placebo Warts were injected intralesionally with 0.1 mL of 1 of the 3 solutions 3 times weekly for 3 weeks.
Outcomes	Outcomes of the trial Cure at 12 weeks
Notes	1 wart per participant was injected. McEwen 1983 was a conference abstract of an RCT of interferon subsequently published in 1986 with Vance as first author (Vance 1986).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details were given.
Allocation concealment (selection bias)	Unclear risk	There was no information about the how the randomisation sequence was concealed (sealed envelopes etc). Comment: Vials were sequentially numbered; therefore, it was unclear if the allocation order was concealed.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The content of the vials were prepared by the manufacturers and were not revealed to participants or personnel. (page 273)
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	It was unclear who did the outcome assessment and if outcome assessors were blinded.
Incomplete outcome data (attrition bias) All outcomes	High risk	100/111 participants completed and were analysed. 5 participants in the 10 IFN group discontinued because of adverse reactions; 6 participants terminated for extraneous reasons, as well as 2 in each treatment group. Comment: Withdrawals because of adverse events in the intervention arm were likely to introduce bias.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.