Associations between patient risk factors, disease severity, and inflammatory markers in community-acquired pneumonia

Community-acquired pneumonia (CAP) remains a major cause of morbidity and mortality, particularly in older adults and patients with chronic co-morbidities. Cytokine patterns and simple hematological indices may improve risk stratification beyond conventional clinical scores. In this prospective single-center study, 41 adults with CAP treated at Kaunas Hospital of Lithuanian University of Health Sciences between November 2024 and March 2025 were enrolled. Clinical data, pneumonia severity index (PSI), complete blood count-derived indices (neutrophil-lymphocyte ratio [NLR], platelet-lymphocyte ratio [PLR], systemic immune-inflammation index [SII]), and serum concentrations of interleukin (IL)-6, IL-8, interferon (IFN)-γ, and G-CSF were obtained on admission (Visit 1) and after 7 days of treatment (Visit 2). Patients were stratified by age (≤65 vs >65 years), co-morbidities, and PSI class. Non-parametric tests and Spearman correlations were applied. The results indicate that patients with co-morbidities and those > 65 years had significantly higher IL-6 levels than younger and non-comorbid patients. IL-6, IFNγ, and G-CSF concentrations were highest at admission and declined by day 7, particularly in PSI Class II patients. Higher PSI classes were associated with increased IL-8, IL-6, and IFNγ. NLR and SII were significantly higher in older patients and in PSI III-IV compared with PSI I-II. IL-6 and G-CSF showed strong positive correlations with NLR and SII, especially in elderly and comorbid patients, whereas PLR displayed weaker and less consistent associations. From these data, it is concluded that in CAP, serum IL-6, IFNγ, and G-CSF reflect age, co-morbidity burden, and disease severity, while NLR and SII closely mirror cytokine-driven systemic inflammation. These readily available indices may serve as cost-effective prognostic markers and, combined with cytokine profiling, could enhance early risk stratification and guide individualized management in CAP.