Various parameters for grading acne vulgaris.

Two 12-week-long double-blind placebo-controlled studies of acne treatments were performed using three judges and a total of 331 male college students. Global severity grades and papule, pustule, and comedo counts were performed every two weeks. The data were evaluated using Pearson's coefficient of correlation, and results showed a high degree of correlation between global severity grades and lesion counts, as well as among judges. These data suggest that acne grading scales and papule counts are equally reproducible methods of grading inflammatory acne and that the comedo grading scale and comedo count are equally reproducible methods of grading comedonal acne.