Is Clear Always Clear? Comparison of Psoriasis Area and Severity Index (PASI) and the Physician’s Global Assessment (PGA) in Psoriasis Clearance

Introduction Psoriasis Area and Severity Index (PASI) and Physician’s Global Assessment (PGA) are the most widely used outcome measures in clinical trials of biologics to treat psoriasis; however, these outcome measures vary in both their reliability and validity. As newer biologics approach complete clearance of psoriasis, it becomes important to have standardized, reproducible forms of measure to accurately compare treatment efficacy. The aim of this study was to evaluate the extent of and reasons for variation between PASI and PGA scores used in clinical trials. Methods A literature search was conducted of clinical trials meeting the inclusion criteria: phase 2 or 3, evaluation of treatment efficacy in reducing psoriasis severity, and use of PASI 90/100 and sPGA or PGA 0/1 as primary end points. Results Among the analyzed studies, 8 of 45 trials had a PASI-PGA variance of < 5%, 4 of 45 trials had a variance of 5–10%, and 33 trials had a variance of > 10%. The IMMvent and AMAGINE trials were the only two trials showing 0 variation between the PASI and PGA scores, testing adalimumab and brodalumab, respectively. Ustekinumab showed the highest variance of 61.9% in the IXORA-S trial. Limitations of this paper include a relatively low number of studies assessed because of the paucity of literature available. Conclusions The use of both PASI and PGA as equivalent assessment tools for complete clearance is redundant and subject to high variability. Novel severity assessments should be developed that reduce calculation variation and take into account patient-oriented symptoms.