A randomised evaluation of the clinical effectiveness of AVOCA silver nitrate for the treatment of verruca pedis

Background: the context and purpose of the study
In the UK, incidence of viral warts and verrucae in children and adolescents is estimated at between 3.9% and 4.9%, with both genders being equally predisposed to HPV infection (Leiding, 2012). The National Morbidity Survey data (1991-1992) suggests that almost two million people in England and Wales will see their General Practitioner for the treatment of cutaneous warts each year, at a cost of an estimated £40 million per annum (Thomas et al, 2006). 95% Silver Nitrate is frequently used in clinical practice; however, has not been evaluated to determine its’ clinical effectiveness. In addition, self administered application of silver nitrate is now commercially available, although awareness of its effectiveness in comparison to the clinical application by a health professional is unknown (Bray, 2007). The aim of this research was to evaluate the clinical effectiveness of using 95% concentration silver nitrate for the treatment of verrucae pedis, comparing professional and self-application methods.

Methods: how the study was performed and statistical tests used.
A Single-centre, two-armed randomized evaluation was conducted at the University Of Huddersfield podiatry clinic. 113 participants (101 analysed) with verruca pedis were recruited voluntarily to this study. Participants were randomized to either a clinical group, where silver nitrate was applied by a healthcare professional; or a home group, where silver nitrate was self-applied. The main outcome measures were; post treatment pain, controlling for pre-treatment pain and resolution of the verruca. An analysis of covariance (ANCOVA) was conducted on the data, using post-treatment VAS pain as the outcome, controlling for pre-treatment pain. An ordinal logistic regression was also conducted on the data, using treatment result as the outcome, with “success” defined to be the reference category.

Results: the main findings
All participants reported a reduction in pain as a result of the intervention. A significant reduction in pain was reported in all the participants who presented with pain prior to treatment (mean pain reduction of 3.98 points on the VAS (SD 2.27)). The study showed no significant difference between the home and the clinically applied treatment of verruca pedis, in either of the primary outcome measures. There was, however, a substantive difference in resolution between groups, with 34.0% full resolution and 26.4 % partial resolution in the clinical treatment group, and 18.8% full resolution and 37.5% partial resolution in the home treatment group.

Conclusions: brief summary and potential implications
Silver nitrate is a safe, cost-effective treatment option for verruca pedis, with equal success rates when compared between home and clinical applications. It provides an alternative option for practitioners which is easy to apply and has no contraindications for patient suitability.

Trial registration:
This clinical evaluation was given ethical ratification via the University of Huddersfield School Research Ethics Panel.