Literature Review: Leukocyte, Neutrophil, and Neutrophil-Lymphocyte Ratio Levels Based on Chest X-Ray Images of Pneumonia Patients
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Abstract
Pneumonia is an infectious disease associated with substantial morbidity and mortality. Inflammatory biomarkers, including leukocyte count, neutrophil count, and the neutrophil-to-lymphocyte ratio (NLR), may support the assessment of inflammatory severity when interpreted alongside chest radiographic findings. This study aimed to review leukocyte, neutrophil, and NLR levels based on chest X-ray findings in patients with pneumonia. A systematic literature review was conducted using the PICOS framework and PRISMA 2020 selection process. Relevant studies published in English between 2020 and 2026 were identified through PubMed, Scopus, ScienceDirect, and Google Scholar. Full-text original research articles examining leukocyte, neutrophil, or NLR levels in pneumonia patients with radiological evaluation were included. Of 7,203 initially identified records, 15 studies met the eligibility criteria and were included in the review. The synthesis showed that patients with more severe pneumonia generally had higher leukocyte counts, neutrophil levels, and NLR values. Increased inflammatory markers were also associated with bacterial pneumonia, extensive pulmonary involvement, lung consolidation, intensive care requirements, prolonged hospitalization, and an increased risk of mortality. Among the evaluated parameters, NLR was the most consistently associated with pneumonia severity and clinical outcomes. However, the reviewed studies used different NLR cut-off values, populations, and study designs, contributing to heterogeneity across findings. In conclusion, leukocyte count, neutrophil count, and particularly NLR are simple and accessible laboratory parameters that may complement chest X-ray findings in evaluating inflammation and pneumonia severity. Further studies are required to establish standardized NLR thresholds for clinical application.
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