[The distribution of biomarkers for Behcet syndrome and their clinical relevance in real-world studies].

Objective: To explore the distribution of different biomarkers for Behcet's syndrome (BS) and their correlation with distinct clinical phenotypes of BS patients in real-world studies. Methods: This study was a retrospective cross-sectional study. A total of 483 patients diagnosed with BS in the Department of Rheumatology and Immunology, Peking University People's Hospital from 2019 to 2022 were enrolled. The baseline information and clinical features of the patients were recorded at their first diagnosis and tested the level of HLA-B51, several auto-antibodies, antistreptolysin-O(ASO), immune globulin, complement in blood serum and interleukin-6 (IL-6). Logistic regression was used to analyze the correlation of biomarkers and phenotypes. Results: Among BS patients, the number of positive cases for HLA-B51, anti-endothelial cell antibody (AECA), antinuclear antibodies (ANA) and ASO was 129, 115, 79 and 54, respectively. The positive rate of other biomarkers was less than 5.0%. About 12.6% of patients with BS had an increased level of IgA (n=61), and 10.8% of patients had an increased level of IgG (n=52). About 41.0% of patients had increased levels of IL-6 (n=198), and 6.4% of patients had decreased levels of IgM (n=31). About 11.2% of patients had decreased levels of C3 (n=54), and 6.0% of patients had decreased levels of C4 (n=29). Elevated IgA was a risk factor for the articular phenotype of BS (OR=2.652, P=0.011). Decreased complement C4 was a risk factor for the neurological phenotype of BS (OR=3.594, P=0.039). Positive ASO was a risk factor for the gastrointestinal phenotype of BS (OR=2.578, P=0.041). Elevated IL-6 was a risk factor for the ocular phenotype of BS (OR=7.560, P=0.016). Conclusion: HLA-B51 and AECA are common biomarkers in BS. Elevated IgA, decreased complement C4, positive ASO, and elevated IL-6 are risk factors for different phenotypes of BS.