Although absolute PASI score is often used to define entry into a trial, it is response to treatment that is important to measure efficacy and outcomes.
There is a gradual tendency, as therapies become more effective to report higher efficacy rates in clinical trials - but aiming high may not be without risk of over-treating some patients.
A method where the advantage of accurate computerized measurement of the area on the digital photograph was combined with physician's proficiency in determination of the edge of psoriatic lesion was published.
Computer-aided measurement of psoriatic lesion area was found to improve the power of the clinical trial, compared to the standard approach.
Attempts have been made to address this problem by providing descriptions of psoriasis severity in evaluation systems, including the Psoriasis Global Assessment (PGA) and the Lattice-System Physician's Global Assessment (LS-PGA); a study compared and validated PASI, PGA, and LS-PGA.