Dynamic assessment of the inflammatory response in military personnel: a pilot study on ΔNLR and composite markers in operational environments

In this pilot study, we investigated immune alterations in 178 military personnel exposed to extreme operational stress. We focused on the neutrophil-to-lymphocyte ratio (NLR) and its change (ΔNLR) alongside composite inflammatory indices- Systemic Inflammation Response Index (SIRI), Systemic Immune-Inflammation Index (SII), and Inflammatory Index Cumulative (IIC). Blood analyses performed before and after deployment revealed a significant post-mission increase in NLR (1.9671±±±0.9174 vs. 1.6079±±±0.4973 pre-deployment), yielding an average ΔNLR of 0.3592±±±0.7642 (<i>P</i> < 0.0001). While basophil counts and several biochemical markers remained stable, notable changes in neutrophils and composite indices suggest a complex inflammatory activation. Importantly, correlation analyses confirmed that despite marked shifts in absolute values, the relative relationships between pre- and post-deployment measurements (e.g., NLR: r = 0.5533, <i>P</i> < 0.0001) were maintained. These findings imply that ΔNLR, together with SIRI, SII, and IIC, may serve as valuable biomarkers for dynamically monitoring the inflammatory response in military contexts, thereby enabling early identification of individuals at increased inflammatory risk.