Quantitative evaluation of severity in psoriatic lesions using three-dimensional morphometry

The severity of psoriasis has been traditionally assessed by measures, such as the psoriasis area and severity index (PASI), the psoriasis severity scores, and the lesional severity scores. As a result, even experienced dermatologists show variations when attempting to determine the severity of psoriasis. Therefore, a better non-invasive and objective measurement of clinical signs is needed. In this study, an instrument, a so-called 'stereoimage optical topometer' (SOT), based on a new concept of 'stereoimaging' was used to measure the three-dimensional skin surface. The aim of this study was to compare the results obtained by the SOT with the visual score of psoriasis lesion. Thirty psoriatic patients were enrolled in this study. Initially, the severity of the infiltration and the scale of 134 psoriatic lesions were assessed by using a visual scoring system (0: none, 1: mild, 2: moderate, 3: severe, and 4: very severe), as scored by five dermatologists. The SOT was then used to quantify the severity of each psoriatic lesion using four three-dimensional SOT parameters (Sa, SL, SA, and SV). Secondly, the involved skin-surface area in the psoriasis cases was scored by the naked eye by the five dermatologists and by image analysis. Statistically significant differences were observed between grades 0, 1, 2, and 3 in terms of the severity measurements of the individual psoriatic lesions by SOT when using the parameters Sa, SL, SA, and SV. Therefore, it was concluded that there is a strong correlation between the results measured by visual scoring and by SOT in psoriasis.