When comparing different active treatments, a noninferiority—also called one-sided equivalence—study design is used. This study design requires the definition of a noninferiority margin, the threshold value of clinical relevance. At present, a noninferiority margin of 10 percentage points is conventionally used for the change in acne lesion counts, but it lacks empirical validation.
We analyzed the data of 4,081 patients with moderate to severe facial acne. The treatment effect was recorded by the investigator as the relative change in lesion counts from baseline (objective assessment). At the end of the treatment period, patients rated themselves as having their acne condition improved, unchanged, or worsened (subjective assessment). We compared the changes in lesion counts with the patients' self-assessment to derive an empirically validated noninferiority margin.
We found that an empirically validated noninferiority margin of 10–15 percentage points for facial acne lesion counts is appropriate.
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