Psoriasis Area and Severity Index Clinical Classification

**Semantic type:** Intellectual Product

**Definition:** A standardized survey developed by Fredriksson and Pettersson in 1978 to calculate the intensity and extent of psoriatic plaques before, during, and after retinoid treatment in chronic plaquetype psoriasis. The instrument utilizes a 5-point rating scale to measure intensity and assigns a numerical score for the percentage of anatomical involvement.

**Synonyms:** - PASI