Evaluation of Serum Immune-Inflammation Index and Serum Inflammatory Response Index in Optic Neuritis

To evaluate the associations and diagnostic performance of inflammatory markers derived from complete blood counts in patients with optic neuritis (ON) and central nervous system (CNS) demyelinating diseases. This retrospective cross-sectional study included 54 patients with ON, 43 patients with CNS demyelinating diseases without ON, and 50 age- and sex-matched healthy controls. The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI) were compared across the groups. Univariate and multivariate logistic regression analyses were performed to assess associations with ON. Receiver operating characteristic (ROC) curves were used to determine diagnostic ability. NLR, PLR, MLR, SII, and SIRI were significantly higher in patients with ON than in controls (all p < .01). NLR achieved the highest area under the curve (AUC = 0.795; sensitivity 75.9%; specificity 72.0%), whereas SII provided the best sensitivity - specificity balance (AUC = 0.768; sensitivity 81.5%; specificity 76.0%). SIRI also demonstrated good discriminatory ability (AUC = 0.748; sensitivity 72.2%; specificity 60.0%). When comparing ON patients with the CNS demyelinating disease group, MLR and SIRI showed modest discrimination (AUC = 0.644 and 0.645, respectively). NLR, PLR, MLR, SII, and SIRI are accessible, inexpensive biomarkers that may support the diagnosis of ON and help identify patients with ON among those with CNS demyelinating diseases. SII provided the best sensitivity - specificity balance for discriminating ON from healthy controls, whereas SIRI may be particularly helpful in differentiating atypical from typical ON.