Agreement and Correlation Between Different Topical Corticosteroid Potency Classification Systems.

Area of Science:

• Dermatology
• Pharmacology
• Epidemiology

Background:

• Topical corticosteroids (TCSs) vary in potency, affecting efficacy and safety.
• Lack of a universal TCS potency classification hinders pharmacoepidemiologic research and clinical interpretation.

Purpose of the Study:

• To classify TCS formulations into three common potency systems.
• To evaluate agreement and correlation between these TCS classification systems.

Main Methods:

• Compiled a list of 232 unique TCS formulations from multiple sources.
• Classified TCSs using the 7-category US system, a 4-category Cochrane review system, and the 4-category WHO ATC system.
• Analyzed agreement using Cohen weighted kappa (κw) and correlation using Spearman rank coefficients (r).

Main Results:

• Found low-to-moderate agreement between the classification systems (κw range: 0.53-0.60).
• Observed strong correlations between all pairs of systems (r range: 0.71-0.77).
• The US classification showed weak agreement with ATC and moderate with Cochrane, while correlations were strong across all.

Conclusions:

• Existing TCS potency classification systems are often incongruent, potentially leading to varied pharmacoepidemiologic study results.
• Transparency in classification methods is crucial for researchers.
• Consideration of alternative potency definitions in sensitivity analyses is recommended.