Varnavides 1997.

Study characteristics
Methods	This study was carried out in a secondary care setting. This study was blinded. Intention‐to‐treat analysis was not carried out. This study was conducted in the UK.
Participants	51 participants were recruited: 9 dropped out. Inclusion criteria of the trial Adults Refractory warts Warts on the hands or feet
Interventions	IFN‐alpha (10 IU/ml weekly X 12) Placebo Intralesional injections were given once weekly for 12 weeks.
Outcomes	Outcomes of the trial Cure at 24 weeks
Notes	1 wart per participant was injected.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote (page 170): "...assigned either interferon alpha or placebo according to a computer‐generated randomised code."
Allocation concealment (selection bias)	Unclear risk	This was unclear; no details were given.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Comment: This was probably done, but while trial or placebo medication was supplied in 'identical 1 ml vials' (page 170) and the trial was stated to be double‐blind, it was not clear how blinding was achieved. However, both participants and personnel were probably blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote (page 170): "Objective assessment was made by a photographic record on slide film at entry..." Comment: This was probably done.
Incomplete outcome data (attrition bias) All outcomes	High risk	9/51 participants did not complete the trial because of adverse effects, attendance, or worsening: 3/9 participants in the intervention group and 6/9 participants in the placebo group. 7/9 participants withdrew because of painful injections/adverse effects; however, groups were not stated. It was unbalanced between the groups.
Selective reporting (reporting bias)	Low risk	All prespecified outcomes were reported.