Abstract
OBJECTIVE: This study aimed to evaluate the clinical utility of novel hematological indices, particularly the systemic immune-inflammation index (SII) and neutrophil-to-lymphocyte ratio (NLR) in diagnosing juvenile idiopathic arthritis (JIA), differentiating its subtypes, and assessing disease activity. METHODS: We conducted a retrospective analysis of 185 JIA patients and 124 healthy controls. Comprehensive clinical and hematological parameters were collected, and immune-inflammatory ratios were calculated. Participants were stratified by JIA subtype according to ILAR criteria and by disease activity based on Wallace criteria. Statistical analyses compared these indices across groups and evaluated their correlations with conventional markers and the JADAS-27 score. Subgroup analyses further assessed their diagnostic potential in patients with normal erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP). RESULTS: SII, NLR, platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR) were significantly elevated in JIA patients compared to controls, with AUC values > 0.6 for JIA identification. Notably, systemic JIA (sJIA) showed distinct inflammatory profiles, with significantly higher SII, MLR, PLR, and NLR, and lower monocyte-to-neutrophil ratio (MNR) and platelet-to-neutrophil ratio (PNR), compared to other subtypes. Active JIA patients exhibited elevated SII and NLR and reduced MNR relative to those with inactive disease. SII and NLR demonstrated moderate positive correlations with ESR, CRP, and JADAS-27, whereas MNR was negatively correlated. Although subgroup analyses in patients with normal ESR/CRP did not reach statistical significance, likely due to sample size limitations-the consistent trends support the potential supplementary role of these indices. CONCLUSION: This study establishes SII and NLR as accessible and informative biomarkers for JIA. They effectively differentiate systemic JIA from other subtypes, reflect disease activity, and correlate with established activity scores. Their low cost and routine availability position them as valuable adjuncts in the diagnostic and monitoring workflow for JIA, particularly when traditional markers are ambiguous or unavailable.