Objective assessment of involved surface area in patients with psoriasis

Background/aims: Although difficult, it is essential to assess the disease severity of psoriasis objectively. The visual grading method currently used for assessing the involved surface area in patients with psoriasis, which is included on the Psoriasis Area and Severity Index (PASI) scoring system, is a subjective method. The aim of this study was to establish the reliable objective method, in estimating the involved surface area in patients with psoriasis. Methods: Thirty patients with psoriasis participated in this study. The skin lesions of each patient were estimated using the visual grading method and an image analysis system. Results: The differences between five dermatologists' estimates of the involved surface area obtained from the visual grading method were highly significant (P < 0.05, Kruskal-Wallis test). The comparison between the visual grading method and the image analysis system showed that the involved areas measured by the visual grading method were significantly higher than those from the image analysis (P < 0.05, Wilcoxon signed rank test). Conclusions: The visual grading method was neither objective nor reproducible. On the other hand, the image analysis system can be used as an objective method of measuring the involved surface area of patients with psoriasis. Therefore, the image analysis system can be used as a standard for the assessment of the involved area of patients with psoriasis.