The purpose of this study is to propose a ranking system for the severity of psoriasis. The consensus method of selecting the indices to include and the classification of real patient profiles by an expert panel to create a gold standard of severity were used. The performance of potential cut-offs was evaluated to create a ranking algorithm. The combined use of PASI, BSA, and sPGA may allow the classification of the severity of psoriatic patients. The final algorithm identifies severe patients in a single step (2 out 3 are met: PASI ≥ 11 or BSA ≥ 10 or sPGA ≥ 3), while two steps are required for mild ((2 out 3 are met: PASI ≤ 3 or BSA ≤ 5 or sPGA ≤ 2) and DLQI < 5) and moderate forms (the patient does not meet 2 out 3 (PASI ≥ 11 or BSA ≥ 10 or sPGA ≥ 3) but has a DLQI ≥ 5. A ranking algorithm is presented, consisting of different measures of disease which classifies psoriatic patients into three categories: mild, moderate, and severe.
Keywords: classification; cut-offs; discrimination; moderate; psoriasis; severity.