Skin hyperpigmentation index in melasma: A complementary method to classic scoring systems

Abstract

Background: Due to relapsing nature of melasma with significant impact on quality of life, an objective measurement score is warranted, especially to follow-up the patients with melasma and their therapy response in a quantitative and precise manner. Aims: To prove concordance of skin hyperpigmentation index (SHI) with well-established scores in melasma and demonstrate its superiority regarding inter-rater reliability. Development of SHI mapping for its integration in common scores. Methods: Calculation of SHI and common melasma scores by five dermatologists. Inter-rater reliability was assessed by intraclass correlation coefficient (ICC) and concordance by Kendall correlation coefficient. Results: Strong concordance of SHI with melasma area and severity index (MASI)-Darkness (0.48; 95% CI: 0.32, 0.63), melasma severity index (MSI)-Pigmentation (0.45; 95% CI: 0.26, 0.61), and melasma severity scale (MSS) (0.6; 95% CI: 0.42, 0.74). Using step function for mapping SHI into pigmentation scores showed an improvement of inter-rater reliability with a difference in (ICC of 0.22 for MASI-Darkness and 0.19 for MSI-Pigmentation), leading to an excellent agreement. Conclusion: Skin hyperpigmentation index could be an important additional cost-and time-conserving assessment method, to follow-up the patients with melasma undergoing brightening therapies in clinical studies, as well as in routine clinical practice. It is in strong concordance with well-established scores but superior regarding inter-rater reliability.