Khattar 2007.

Study characteristics
Methods	This study was carried out in a secondary care setting. This study was blinded. Intention‐to‐treat analysis was carried out. This study was conducted in the USA.
Participants	44 participants were recruited: None dropped out. Inclusion criteria of the trial Participants aged > 12 Ordinary or refractory warts not specified The site was not specified
Interventions	15% salicylic acid and 15% lactic acid combination ointment versus 20% zinc oxide These were applied twice daily, over 3 months.
Outcomes	Outcomes of the trial Cure at 3 months
Notes	The number of warts per participant ranged from 1 to 41, and the study was aiming for cure of all warts in each participant. There was a higher mean number of warts in the zinc oxide group (5.1 versus 4.3), and participant compliance was not assessed.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote (page 427): "Patients were assigned randomly to two groups." Comment: The method of randomisation was unclear.
Allocation concealment (selection bias)	Unclear risk	The allocation concealment was unclear.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	The medication was labelled A or B; therefore, participants were unaware which treatment they were receiving. Personnel were blinded. Quote (page 427): "At the end of the study the pharmacist informed the primary investigator that arm A was 20% zinc oxide and arm B was the 15% alicyclic acid." Comment: This was probably done for both participants and personnel.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	It was not specifically stated that outcome assessors were blinded. Comment: This was judged as probably done as the personnel were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	9/44 participants withdrew: 6/22 in the zinc oxide group and 3/22 in the SA‐LA group. Reasons were not stated. There be may be a source of bias arising from 1 participant with 41 warts who withdrew.
Selective reporting (reporting bias)	Low risk	All outcomes were reported.