Background: Infections continue to be a major cause of morbidity and mortality globally, particularly in low- and middle-income countries. Early identification of disease severity and differentiation of infection types are crucial for effective management. The neutrophil-to-lymphocyte ratio (NLR), derived from routine blood investigations, has emerged as a potential marker of systemic inflammation. Objectives: To evaluate the neutrophil-to-lymphocyte ratio as an inflammatory marker in patients with infections and to assess its association with disease severity and type of infection. Methods: A hospital-based cross-sectional analytical study was conducted in a tertiary care hospital in Uttar Pradesh from January 2022 to December 2022. A total of 270 patients diagnosed with infections were included using consecutive sampling. Demographic and clinical data were collected using a semi-structured proforma. NLR was calculated from complete blood count parameters. Statistical analysis was performed using SPSS version 25.0, and associations were assessed using appropriate inferential tests, with p<0.05 considered statistically significant. Results: Among the 270 participants, the majority were aged 31–50 years, with a male predominance. Bacterial infections were the most common. The mean NLR was 4.9 ± 2.3, with most patients exhibiting moderate NLR values. A significant association was observed between NLR and disease severity, with higher values in severe infections (p<0.001). Additionally, NLR was significantly associated with the type of infection (p=0.002), with higher values seen in bacterial infections compared to viral infections. Conclusion: NLR is a simple, accessible, and effective marker of inflammation that correlates with disease severity and type of infection. It can be utilized as an adjunct tool for early diagnosis, risk stratification, and guiding clinical management, particularly in resource-constrained settings.

Neutrophil-to-lymphocyte ratio; Infections; Inflammation; Biomarkers; Disease severity; Bacterial infections; Hematological parameters