Implementation of blinded outcome assessment in the Effective Verruca Treatments trial (EverT) – lessons learned

Cockayne, S; Hewitt, C; Hashmi, F; Hicks, K; Concannon, M; McIntosh, C; Thomas, K; Hall, J; Watson, J; Torgerson, D; Watt, I

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.
Trial registration ISRCTN Registry ISRCTN18994246
Keywords: blinding; digital photographs; outcome assessment; randomised controlled trial

Citation

Cockayne, S., Hewitt, C., Hashmi, F., Hicks, K., Concannon, M., McIntosh, C., …Watt, I. (2016). Implementation of blinded outcome assessment in the Effective Verruca Treatments trial (EverT) – lessons learned. Journal of Foot and Ankle Research, 9(21), https://doi.org/10.1186/s13047-016-0155-4

• Journal Article Type: Article
• Acceptance Date: Jul 8, 2016
• Online Publication Date: Jul 12, 2016
• Publication Date: Jul 12, 2016
• Deposit Date: Jul 15, 2016
• Publicly Available Date: Jul 25, 2016
• Journal: Journal of Foot and Ankle Research
• Publisher: Springer Verlag
• Volume: 9
• Issue: 21
• DOI: https://doi.org/10.1186/s13047-016-0155-4
• Publisher URL: http://dx.doi.org/10.1186/s13047-016-0155-4
• Related Public URLs: https://jfootankleres.biomedcentral.com/
• Additional Information: Funders : HTA; Projects : EVerT