Use of chromametry and digital photography for objective measurement of skin color in clinically normal dogs

OBJECTIVE: To evaluate whether skin erythema in clinically normal dogs can be quantified by use of chromametry and image analysis of digital photographs. ANIMALS: 9 German Shepherd Dogs and 10 mixed-breed dogs. PROCEDURE: Hair was clipped at 7 sites on the body. Skin erythema was evaluated at the axillary region, right and left lateral aspect of thorax, right and left loin area (ie, part of the back between the thorax and pelvis), right and left groin area (ie, the junctional region between the abdomen and thigh), metatarsal digital pad, and on the nose. Replicate measurements were done by use of chromametry and image analysis of digital photographs, using erythema values in accordance with the Committee International d'Eclairage (CIE)-Lab color system. RESULTS: Repeatability was high for both techniques. Within-dog variation was lower than between-dog variation. Between-dog variation was high for both groups of dogs. Interregional variation was significant in German Shepherd Dogs and mixed-breed dogs. Erythema values revealed symmetry between the right and left lateral aspects of the thorax and loin and groin areas. CONCLUSIONS AND CLINICAL RELEVANCE: Precise objective methods are available for skin erythema quantification. Chromametric and photographic erythema values had a high within-dog reproducibility. Between-dog variability was high for German Shepherd Dogs and mixed-breed dogs as was regional variation, indicating differences in color among dogs.