Validation and Responsiveness of the Rosacea Area and Severity Index in a Chinese Cohort: A Comparative Study with the Investigator's Global Assessment.

The Rosacea Area and Severity Index (RASI) is a recently developed tool for assessing rosacea severity, but its validation has so far been limited, requiring further independent evaluation. This study aimed to comprehensively assess the reliability, validity and responsiveness of the RASI in a Chinese cohort. Six trained observers independently evaluated standardized photographs of 230 Chinese patients with rosacea using both the RASI and the Investigator's Global Assessment (IGA). Round 1 assessment was used to determine interobserver reliability and convergent validity, while a subgroup of 60 patients was reassessed to evaluate intraobserver reliability and responsiveness (Round 2). In this subgroup, baseline and 1-month follow-up photographs were rescored after 3 months by the same observers. Results showed moderateto-strong correlations between RASI and IGA at baseline, supporting validity. Interobserver reliability was high for both RASI and IGA overall scores, with intraclass correlation coefficients of 0.923 and 0.935. Intraobserver reliability showed no significant deviation (p>0.05). For responsiveness, RASI demonstrated a higher standardized response mean than IGA (0.43 vs 0.37) with a similar effect size. Additionally, RASI detected statistically significant changes (p<0.001) in patients classified as "stable" by IGA. Overall, RASI showed robust reliability, validity and superior responsiveness.