The Brazilian version of Skindex-16 is a valid and reliable instrument to assess the health-related quality of life of patients with skin diseases

Introduction
The aim of this study was to assess the psychometric properties of the Brazilian version of Skindex-16 in patients with various skin diseases.
Methods
Dermatologic assessments were performed for the diagnosis and classification of the severity of skin conditions. The clinical feasibility of Skindex-16 was assessed based on the time required to complete the questionnaire and the number of unanswered items. The participants (n = 110) answered the Hospital Anxiety and Depression Scale (HADS), the Dermatology Life Quality Index (DLQI) and the Skindex-16 (Portuguese/Brazil version) questionnaires. Convergent validity was assessed based on the correlation of the Skindex-16 with the DLQI and HADS subscales. Known-groups validity was assessed based on the comparison of the mild, moderate and severe disease groups using the Kruskal-Wallis test. Internal consistency was assessed using Cronbach’s alpha and test-retest reproducibility using the intraclass correlation coefficient (ICC) obtained with 29 participants who answered the Skindex-16 a second time 3 to 10 days after the first assessment.
Results
The mean time to answer the questionnaire was 2 min 41 sec. Cronbach’s alpha scores were 0.867, 0.930 and 0.888 for the Skindex-16 domains symptoms, emotions and functioning, respectively. The ICCs were 0.947, 0.860 and 0.843 for the Skindex-16 domains symptoms, emotions and functioning, respectively. All three Skindex-16 scales exhibited strong correlations with DLQI. Moderate correlations were found between HADS subscales and the Skindex-16 emotions domain. Known-groups validity showed differences in all three Skindex-16 domains between the mild and moderate skin disease groups (emotions: p < 0.001; symptoms: p = 0.049; functioning: p < 0.001) and between the mild and severe skin disease groups (emotions: p = 0.002; symptoms: p = 0.001; functioning: p = 0.002).
Conclusion
The Portuguese/Brazil version of Skindex-16 is a valid and reliable instrument to assess the quality of life of patients with skin diseases.