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  • Ivan Bristow

Clinical Classification of Warts

Warts are a common clinical problem affecting predominantly children but also a subset of adults. It is well known there are many sub-types of the human papilloma virus (HPV). Different sub-types can potentially mean different clinical presentations and theoretically could mean different responses to various treatment modalities.

In an ideal world, it would be good to have a simple tool to assess lesions on their clinical characteristics which could act as a baseline and allow treatment comparisons to take place. For cutaneous warts, in 1985 Jablonska and colleagues (1) attempted to develop such a clinical tool but this was not widely adopted. However, earlier this year a paper was published in the British Journal of Dermatology investigating the development and validation of a clinical assessment tool known as the “CWARTS” (Cutaneous Warts) diagnostic tool. Hoogendorn and colleagues (2) using the clinical expertise of a dermatologist and two GP’s developed, alongside a literature review, 9 clinical criteria that they believed could determine wart morphology.

The dichotomous criteria used included:

Arrangement (solitary / confluent)

Level (Raised or flat)

Aspect (Rough / lobed or smooth /not lobed)

Border (sharply defined or not)

White skin flakes (present or not)

Black dots (present or not)

Colour (Yellow or red)

Border (erythema or no border erythema)

Overlying callus (present or not present)

This was subsequently tested in two parts. Firstly, by asking 28 experienced physicians to classify 10 clinical images of warts using the system and then in the second phase, six observers scored 299 images (twice over a period of 7 days). This set out to measure inter and intra-observer agreement and finally it was statistically evaluated using the Intra-class Correlation Coefficient (ICC). The results showed that for most criteria the interobserver correlation was good and, as they suggest, therefore be a reliable clinical tool. The presence of black dots was particularly high in agreement as a discriminating factor. Level was the lowest discriminating factor but as the authors point out this is probably because photographs were used so depth perception for the assessors would have been limited. As the authors suggest the tool could be adapted for other types of wart (genital for example) and should undergo more research in clinical practice and possibly be taken further to assess the severity of cutaneous wart infection.

So clinically for the podiatrist what could this mean? As with any tool, it could be adopted in clinic to assess plantar warts. Data collected from this could help to standardise diagnosis. Where the strength of this tool will lie will probably be more to do with treatment outcomes. For example, do certain types of wart respond better to certain types of treatments? In many ways that is the million-dollar question but the researchers of this paper have already begun to explore this (3), albeit in a limited manner, but suggesting there may be a case for clearer wart identification prior to treating in the future.


1. Jablonska S, Orth G, Obalek S, Croissant O. Cutaneous warts clinical, histologic, and virologic correlations. Clin Dermatol. 1985;3(4):71-82.

2. Hogendoorn GK, Bruggink SC, Hermans KE, Kouwenhoven STP, Quint KD, Wolterbeek R, et al. Developing and validating the Cutaneous WARTS (CWARTS) diagnostic tool: a novel clinical assessment and classification system for cutaneous warts. Br J Dermatol. 2018;178(2):527-34.

3. Hogendoorn GK, Bruggink SC, de Koning MNC, Eekhof JAH, Hermans KE, Rissmann R, et al. Morphological characteristics and HPV genotype predict the treatment response in cutaneous warts. Br J Dermatol. 2018;178(1):253-60.


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