Serum IL-32γ as a biomarker for remission assessment in systemic lupus erythematosus
Background To investigate the potential of serum interleukin (IL)-32γ levels as a biomarker for assessing lupus low disease activity state (LLDAS) and remission, the targets of a treat-to-target strategy, in patients with systemic lupus erythematosus (SLE). Methods We analyzed sera from 40 patients with SLE. Serum IL-32γ levels were measured using an enzyme-linked immunosorbent assay, alongside conventional serologic markers (C3, C4, anti-double-stranded DNA antibody). Disease status was classified according to LLDAS, definition of remission in SLE (DORIS) remission, and glucocorticoid (GC)-free remission. Correlations with SLE disease activity index 2000 (SLEDAI-2K) were examined using Spearman’s rank correlation coefficient, and receiver operating characteristic (ROC) curve analyses were performed to evaluate discriminative accuracy for disease state. Results Serum IL-32γ levels correlated significantly with SLEDAI-2K (rho=0.401, p=0.010), as did the conventional serologic markers. In ROC analyses, IL-32γ was statistically significant in discriminating LLDAS (area under the curve [AUC]=0.728, p=0.014), similar to the other conventional serologic markers. However, for more stringent definitions, IL-32γ was the only serologic marker that retained statistical significance (DORIS remission: AUC = 0.785, p=0.014; and GC-free remission: AUC = 0.831, p=0.007). Conclusion Serum IL-32γ is significantly associated with overall disease activity and shows promising discriminatory ability for disease states in SLE. Notably, it retains discriminative capacity in stringent remission definitions, underscoring its potential as a novel biomarker. These findings suggest that IL-32γ could complement existing tools in treat-to-target strategies, offering a simple serologic marker to guide therapy toward the ultimate goal of GC-free remission.