The psychosocial impact of psoriasis is well documented. However, the contributing role of clinical disease characteristics is not satisfactorily explored. This study aimed to validate the Self-administered Psoriasis Area and Severity Index (SAPASI) to a Portuguese population (SAPASI-PT) and to perform its cross-validation, assessing how the results will generalize to an independent data set, with the Psoriasis Area and Severity Index (PASI), in order to assess the influence of psoriasis\' severity on psychosocial disability and psychopathology.
A cross-sectional study with 228 patients with psoriasis was carried out. Data was collected through a sociodemographic and clinical questionnaire, SAPASI-PT, the Psoriasis Disability Index (PDI) and the Brief Symptoms Inventory (BSI). The cultural and linguistic adaptation of SAPASI to a Portuguese version and the cross validation with PASI was carried out. Multiple associations between psychosocial disability, psychopathology and severity, discomfort and location of lesions were investigated through logistic regression models.
A good adjustment model for SAPASI-PT is found. Also, associations between psychosocial disability, psychopathology and the psoriasis severity and discomfort are found. The existence of lesions is positively associated with the severity of the disease. Patients with lesions in hands or genitals are those reporting a greater discomfort. The presence of lesions in hands is positively associated with PDI, i.e., with leisure and with treatment, marginally. Additionally, patients scoring higher in the personal dimension are found to have a significantly greater percentage of lesions in the genitals.
The psoriasis severity and location of lesions are important determinants of patients´ quality of life. Lesions on face, hands and genitals are associated with a higher impact on psychosocial wellbeing of patients. Psychological counselling should be considered within psoriasis treatment context in patients with the described disease manifestations.

Aims: This study aims to develop a mapping algorithm that can be used to predict 5-level EQ-5D (EQ-5D-5L) utility scores from the Psoriasis Disability Index (PDI) for further use in cost-utility analysis among psoriasis patients.Materials and Methods: A total of 321 participants with psoriasis was recruited in a dermatology clinic from a tertiary hospital in China. The EQ-5D-5L utility scores were scored using the Chinese-specific value set. Three model specifications were used and each one was estimated using three different statistical techniques, including the ordinary least squares (OLS), the Tobit regression and the generalized linear model (GLM). The goodness-of-fit of mapping performance was estimated by using two common indicators: the mean absolute error (MAE) and the mean square error (MSE).Results: A final validated sample of 321 psoriasis patients was analyzed in the study. The patients had a mean ± standard deviation (SD) age of 39.7 ± 12.9 years, and the EQ-5D-5L state utility score is 0.899 ± 0.106. Among all the models considered, the OLS linear model based on the four PDI item scores was selected as the best model due to higher accuracy (MAE = 0.1334 and 0.1557 for the estimation and validation sample separately).Limitations: The main limitation of this study is that the survey site was limited to one hospital and not more broadly representing the whole of China. Additionally, there are some missing data in the full sample and an absence of an external dataset to validate the algorithms.Conclusions: The mapping algorithms reported in this paper can be used to predict the EQ-5D-5L utilities from the PDI; however, similar to other mapping studies in the literature it can only serve as the second-best approach to elicit utilities from disease-specific instruments.