Prevalence of psoriasis and associated risk factors in China: protocol of a nationwide, population-based, cross-sectional study.

Introduction: Psoriasis is a chronic inflammatory skin disease which could lead to serious complications and increased risk of cardiovascular diseases. Psoriasis was recognised as a serious non-communicable disease with important public health impact by member states in the World Health Assembly resolution in 2014. However, data on psoriasis epidemiology are scarce worldwide, especially from low-income and middle-income countries. Only a few epidemiological studies on psoriasis have been conducted in parts of China, mostly without appropriate sampling design and data analysis.

Aim: This study aims to obtain the prevalence of psoriasis in China and relevant risk factors through a nationwide, population-based study with adequate statistical design.

Methods And Analysis: This is a cross-sectional study to be conducted in 60 sites across China. A multistage, cluster random sampling design is used. Participants should have local household registration or be residing in the survey area for at least 6 months during the past year. The presence of psoriasis is ascertained independently by two certified dermatologists. If any discrepancies in the diagnosis occur, consensus will be met via discussion. All participants will be interviewed with a questionnaire to collect sociodemographic and disease information. The field survey will be implemented from October 2018 to June 2019. All statistical analyses will be conducted using survey procedures in SAS V.9.2 software to adjust for the complex sample design.

Ethics And Dissemination: The study has been reviewed and approved by the ethics committee of the Institute of Dermatology, Chinese Academy of Medical Sciences and Peking Union Medical College (Nanjing, China). A written informed consent will be obtained from all participants before the questionnaire survey. Findings of the study will be disseminated through publications in peer-reviewed journals.