Evaluation of Erythema Severity in Dermatoscopic Images of Canine Skin: Erythema Index Assessment and Image Sampling Reliability.

Blaž Cugmas,Daira Viškere,Thierry Olivry,Eva Štruc

doi:10.3390/s21041285

Abstract

The regular monitoring of erythema, one of the most important skin lesions in atopic (allergic) dogs, is essential for successful anti-allergic therapy. The smartphone-based dermatoscopy enables a convenient way to acquire quality images of erythematous skin. However, the image sampling to evaluate erythema severity is still done manually, introducing result variability. In this study, we investigated the correlation between the most popular erythema indices (EIs) and dermatologists’ erythema perception, and we measured intra- and inter-rater variability of the currently-used manual image-sampling methods (ISMs). We showed that the EIBRG, based on all three RGB (red, green, and blue) channels, performed the best with an average Spearman coefficient of 0.75 and a typical absolute disagreement of less than 14% with the erythema assessed by clinicians. On the other hand, two image-sampling methods, based on either selecting specific pixels or small skin areas, performed similarly well. They achieved high intra- and inter-rater reliability with the intraclass correlation coefficient (ICC) and Krippendorff’s alpha well above 0.90. These results indicated that smartphone-based dermatoscopy could be a convenient and precise way to evaluate skin erythema severity. However, better outlined, or even automated ISMs, are likely to improve the intra- and inter-rater reliability in severe erythematous cases.

Highlights

Canine atopic dermatitis (AD) is a chronic allergic and inflammatory skin disease with characteristic clinical features [1]
The single best and worse correlations between optical and visual erythema assessment resulted in rs of 0.83 and 0.55, respectively
We found a strong correlation between the optical (EIBRG and PT) and the dermatologists’ visual erythema severity estimates

Summary

Introduction

Canine atopic dermatitis (AD) is a chronic allergic and inflammatory skin disease with characteristic clinical features [1]. It is one of the most common skin diseases in dogs, with a prevalence of 3–15% [2]. Few disease severity scales have been developed to grade the clinical signs of canine AD. Skin lesions are evaluated most often with the fourth iteration of the Canine Atopic Dermatitis Extent and Severity Index (CADESI4) [1]. Since the CADESI4 is not very sensitive to short-term changes of chronic skin lesions, such as hair loss or increased skin thickness, the scale’s derivative-based only on erythema evaluation has been proposed [5]

Methods

Results

Discussion

Conclusion