The association between Behçet disease activity and elevated systemic immune-inflammation index: A retrospective observational study in a tertiary care hospital.

Background The systemic immune-inflammation index (SII) is a novel marker for predicting the prognosis in patients with various diseases and cancers. We aimed to investigate the relationship between SII and disease activity in patients with Behçet disease (BD). Methods Our retrospective study included 513 patients with BD aged ≥18 years. The patients were classified into an active group (n=355) and an inactive group (n=158). Pearson correlation analysis was performed to elucidate correlations between the SII and other markers. Binary logistic regression analysis was used to determine BD-related risk factors. Receiver operating characteristic (ROC) curves were computed to assess cut-offs for the predictive value of the SII and other markers. Results Patients with active BD had a significantly higher SII (p<0.001) than those in the inactive group. ROC analysis revealed that the optimal SII cut-off value to identify BD activity was 526.23, with 70.4% sensitivity and 70.3% specificity. Pearson correlation coefficient (r) demonstrated a significant positive correlation between SII, and the C-reactive protein level (r=0.427, p<0.001), erythrocyte sedimentation rate (r=0.422, p<0.001), platelet- lymphocyte ratio (r=0.711, p<0.001), and neutrophil- lymphocyte ratio (r=0.672, p<0.001). According to binary logistic regression analysis, the SII (odds ratio [OR] 1.003; 95% confidence interval [CI] 1.001-1.004; p=0.002) was an independent risk factor for active BD. Conclusion The SII can be considered a novel predictor of BD activity.