Decoding Inflammation: The Role of Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio in Predicting Critical Outcomes in COVID-19 Patients.

Background and Objectives: The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are novel biomarkers that provide insight into systemic inflammation and how the immune system responds to stress or infection. These ratios have been associated with predicting clinical outcomes in various diseases, including COVID-19. This study aims to evaluate the prognostic value of NLR and PLR in anticipating ICU admission, acute respiratory failure, and disease severity in COVID-19 patients. Materials and Methods: We conducted a retrospective, observational study that included 536 patients diagnosed with COVID-19. We analyzed the NLR and PLR values at admission and correlated them with ICU admission, the onset of acute respiratory failure, and clinical outcomes. Results: Statistical correlations were identified between elevated NLR and PLR values and the development of complications during hospitalization (p = 0.04 and p = 0.00), acute hypoxemic respiratory failure (p = 0.00), and admission to the intensive care unit (ICU) (p = 0.04). No correlations were found between the values of these ratios and mortality (p = 0.46 and p = 0.32) nor with the development of hepatic cytolysis (p = 0.79 and p = 0.87). Conclusions: NLR and PLR are reliable, easily obtainable biomarkers that can aid in the early prediction of ICU admission and disease severity in COVID-19 patients, offering valuable insights for risk stratification and clinical management. Further prospective studies are needed to validate these biomarkers as part of a broader predictive model for critical care in COVID-19.