title: Implementation of blinded outcome assessment in the Effective Verruca Treatments trial (EverT) - lessons learned.
abstract: BACKGROUND
  Trials using inadequate levels of blinding may report larger effect sizes than blinded studies. It has been suggested that blinded outcome assessment in open trials may in some cases be undertaken by assessments of photographs. The aim of this paper is to explore the effect of using different methods to assess the primary outcome in the EVerT (Effective Verruca Treatments) trial. It also aims to give an overview of the experiences of using digital photographs within the trial.
  
  
  METHODS
  We undertook a secondary analysis to explore the effect of using three different methods to assess the primary outcome in the EVerT trial: assessment of digital photographs by blinded healthcare professionals; blinded healthcare professional assessment at the recruiting site and patient self-report. The verruca clearance rates were calculated using the three different methods of assessment. A Cohen's kappa measure of inter-rater agreement was used to assess the agreement between the methods. We also investigated the experiences of healthcare professionals using digital photographs within the trial.
  
  
  RESULTS
  Digital photographs for 189 out of 240 (79 %) patients in the trial were received for outcome assessment. Of the 189 photographs, 30 (16 %) were uninterpretable. The overall verruca clearance rates were 21 % (43/202,) using the unblinded patient self-reported outcome, 6 % (9/159,) using blinded assessment of digital photographs and 14 % (30/210,) using blinded outcome assessment at the site.
  
  
  CONCLUSIONS
  Despite differences in the clearance rates found using different methods of outcome assessment, this did not change the original conclusion of the trial, that there is no evidence of a difference in effectiveness between cryotherapy and salicylic acid. Future trials using digital photographs should consider individual training needs at sites and have a backup method of assessment agreed a priori.
  
  
  BACKGROUND
  ISRCTN Registry ISRCTN18994246.
authors.affiliation: Department of Health Sciences, York Trials Unit, University of York, York, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Cockayne
authors.affiliation: Department of Health Sciences, York Trials Unit, University of York, York, UK.
authors.forename: Catherine
authors.initials: C
authors.lastname: Hewitt
authors.affiliation: School of Health Sciences, University of Salford, Salford, UK.
authors.forename: Farina
authors.initials: F
authors.lastname: Hashmi
authors.affiliation: Department of Health Sciences, York Trials Unit, University of York, York, UK.
authors.forename: Kate
authors.initials: K
authors.lastname: Hicks
authors.affiliation: The School of Human & Health Sciences, Division of Podiatry, University of Huddersfield, Huddersfield, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Concannon
authors.affiliation: Discipline of Podiatry, The National University of Ireland, Galway, Republic of Ireland.
authors.forename: Caroline
authors.initials: C
authors.lastname: McIntosh
authors.affiliation: Centre of Evidence Based Dermatology, University of Nottingham, Nottingham, UK.
authors.forename: Kim
authors.initials: K
authors.lastname: Thomas
authors.affiliation: The Usher Institute of Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, UK.
authors.forename: Jill
authors.initials: J
authors.lastname: Hall
authors.affiliation: Department of Health Sciences, York Trials Unit, University of York, York, UK.
authors.forename: Judith
authors.initials: J
authors.lastname: Watson
authors.affiliation: Department of Health Sciences, York Trials Unit, University of York, York, UK.
authors.forename: David
authors.initials: D
authors.lastname: Torgerson
authors.affiliation: Department of Health Sciences, York Trials Unit, University of York, York, UK ; Hull York Medical School, York, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Watt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D017679:Cryotherapy; D005260:Female; D005534:Foot Diseases / Q000188:drug therapy / Q000628:therapy*; D006801:Humans; D007641:Keratolytic Agents / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000379:methods*; D010781:Photography / Q000379:methods; D012107:Research Design; D020156:Salicylic Acid / Q000627:therapeutic use; D012648:Self Care / Q000379:methods; D057566:Self Report; D016037:Single-Blind Method; D016896:Treatment Outcome; D014860:Warts / Q000188:drug therapy / Q000628:therapy*; D055815:Young Adult
chemical_list: D007641:Keratolytic Agents; D020156:Salicylic Acid
keywords: Blinding; Digital photographs; Outcome assessment; Randomised controlled trial