Identifying the Zheng in psoriatic patients based on latent class analysis of traditional Chinese medicine symptoms and signs

BACKGROUND There are approximately five Zhengs reported in psoriatic patients. Systematic data collection and proper analysis for the classification of psoriasis have been lacking. This study aims to cluster the Zhengs in psoriatic patients based on the application of a checklist of traditional Chinese medicine (TCM) symptoms and signs followed by latent class analysis (LCA). METHODS A cross-sectional study of 507 psoriatic patients aged above 10 years was performed in Yunnan Provincial Hospital of TCM and the First Affiliated Hospital of Kunming Medicine University from October 2010 to September 2011 using a TCM symptoms and signs checklist obtained from 16 TCM experts by the Delphi technique. LCA was applied to obtain the best fitted model for clustering of symptoms and signs that can be interpreted as underlying Zhengs of psoriasis. RESULTS The LCA identified three Zhengs: dampness-heat Zheng (35.1%); blood heat Zheng (34.7%); and yin deficiency and blood dryness Zheng (30.2%). The first Zheng was associated with winter, the second with male sex, old age, smoking, and drinking alcohol, and the third with outpatient status, which reflected a mild disease course. CONCLUSIONS In this study, 507 psoriasis patients were clustered into three Zhengs, which had different associated factors.