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Correlation of photographic images from the Leeds revised acne grading system with a six-category global acne severity scale


  • Conflict of interest
    Dr. Tan has been an advisory board member, speaker, consultant and/or investigator for Bayer, Galderma, Photocure, Stiefel/GSK and Valeant.

  • Funding source
    This study was supported by a grant from Stiefel Laboratories.

J. Tan.


Background  Few global acne grading systems include individualized assessments of chest and back as well as face. The Leeds revised acne grading system is based on photographic images while the Comprehensive Acne Severity Scale (CASS) is based on textual descriptions. There exists an unmet need for a global scale based on both text and photos.

Purpose  Our objective was to evaluate the correspondence of severity grades from descriptive text (CASS grades) for each Leeds image.

Methods  Twenty-three dermatologists independently graded 56 photos of face, chest and back of varying acne severity using CASS. Photographs were randomly presented from the The Leeds revised acne grading system (n = 31) and from acne patients of the corresponding author (= 25). For each Leeds photo, rater responses for CASS grades were transformed into median, coefficient of variation and percentiles.

Results  High rater agreement (≥75%) was observed for Leeds facial inflammatory 2 (CASS 3), 4 (CASS 4), 6 (CASS 4), 9–12 (all CASS 5); Leeds facial comedonal A (CASS 2); Leeds chest 7 and 8 (both CASS 5); and Leeds back 7 and 8 (both CASS 5). Lowest coefficients of variance were observed in Leeds facial inflammatory 4, 9, 10, 11; Leeds facial comedonal A; Leeds chest 7 and 8; and Leeds back 8.

Conclusions Leeds photos, by inadequately portraying facial acne grades 1 (almost clear) and 2 (mild) and back and chest grades 1–4 (almost clear to severe), cannot accurately represent the spectrum of severity in a six-category global acne scale. Accordingly, there is a current need for images that correspond to a categorical acne scale.

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