Practical understanding of mean percent psoriasis area and severity index reduction for biologics

Psoriasis in clinical trials is often measured by the Psoriasis Area and Severity Index (PASI). This measurement is well understood by clinical trialists and many dermatologists but rarely by patients and some clinicians. Patients may not understand their chance of improvement based on a PASI-50 or PASI-75 value (50 or 75% improvement in PASI score). They would better understand a PASI average presented as the mean percent improvement in the PASI score from baseline.

This article simplifies these terms of reduction from baseline in PASI scores as related to treatment with biologic agents. This may be more meaningful for patients and clinicians when discussing their average chance of improvement.