Longitudinal Changes in Neutrophil-to-Lymphocyte and Monocyte-to-Lymphocyte Ratios During Multiple Sclerosis Relapse

Background: The neutrophil-to-lymphocyte ratio (NLR) and monocyte-to-lymphocyte ratio (MLR) reflect the balance between innate and adaptive immunity and may indicate systemic inflammation. Objectives: To evaluate longitudinal changes in NLR and MLR in MS patients during relapse compared with relapse-free controls. Methods: In this retrospective single-center observational study, patients with MS were followed for 2 years. Individuals with at least one relapse and complete blood count data at predefined time points were included. Controls without relapse were selected in a 2:1 ratio and matched for age, sex, disease duration, EDSS score, and disease-modifying therapy category. NLR and MLR were assessed 3 months before relapse (or index date), during relapse, and 3 months after. Results: The study included 34 patients with relapse and 68 controls. During relapse, patients showed higher neutrophil and monocyte counts, lower lymphocyte counts, and elevated NLR and MLR compared with controls (all p < 0.001). NLR increased from 2.75 pre-relapse to 3.62 during relapse, then decreased to 2.67 (p = 0.0002). MLR rose from 0.45 to 0.54 and declined to 0.40 (p = 0.002). No significant changes were observed in controls. Conclusions: NLR and MLR demonstrated dynamic changes during MS relapse. These non-specific indices may serve as exploratory, complementary markers of relapse-associated inflammation, but require validation in larger prospective studies including MRI correlates.