Erythema-directed digital photography and colorimeter scores correlate with rosacea erythema evaluation in patients under treatment with topical ivermectin

Inflammatory rosacea is clinically characterized by persistent erythema and inflammatory lesions. Its severity is generally based on clinical observation that may be cumbersome. The aim of this study was to assess if erythema-directed digital photography (EEDP) and colorimeter (COL) correlate and are concordant with clinical evaluation of erythema degree of rosacea under topical treatment. Thirty naïve patients with mild/moderate inflammatory rosacea were instructed to apply ivermectin cream for 8 weeks. Erythema degree was performed at baseline, and at 2, 4, 6, and 8 weeks by clinician erythema assessment based on 5-point severity scale (from 0 = no erythema to 4 = fiery redness), and by instrumental evaluation by EDDP using the same 5-point scale of clinical assessment and by COL using a 5-point scale (from 0 = <1 units = no erythema to 4 > 12 units = fiery redness). Concordance and correlation analysis were performed using Cohen's Kappa coefficient and Correlation Coefficient test respectively. At baseline a statistically significant concordance/correlation value between EDDP and COL was observed. At 2 weeks, the statistical concordance/correlation value between instrumentals were both increased, along with a slight significant concordance between clinical assessment and erythema-directed digital photography. At 4, 6 and 8 weeks, a statistically significant increase of concordance/correlation value among all the considered parameters from baseline was found. The results of our study showed that at baseline and during the early treatment stage both EDDP and COL were able to appreciate more accurately the erythema grade compared to clinical observation supporting the use of non-invasive techniques for a more objective evaluation of erythema in rosacea.