Fig. 1

Study design and flow diagram. A total of 563 tongue coating samples from different regions of China were collected prospectively. After rigorous diagnosis and exclusion procedures, 535 tongue coating samples were included for analysis, including 213 SLE (140 treatment-naïve patients and 73 posttreatment patients) from Zhengzhou, 280 HC from Zhengzhou, and 42 treatment-naïve SLE patients from Haikou. The treatment-naïve samples from Zhengzhou were randomly divided into a derivation cohort and a validation cohort based on a random number table. The derivation cohort was used to characterize the oral microbiome of SLE, identify key microbial markers, and constructed an SLE classifier. The validation and cross-regional validation cohorts were used to evaluate the diagnostic efficacy of the classifier. We further characterized the oral microbiome of 73 posttreatment SLE patients and 146 HC. HC healthy controls, SLE systemic lupus erythematosus, RFC random forest classifier model