Neutrophil to Lymphocyte Ratio: An Emerging Marker of the Relationships between the Immune System and Diseases

Over the last 10 years, the evaluation of the neutrophil-to-lymphocyte ratio (NLR) as an emerging marker of diseases has become a compelling field of bio-medical research. Although a precise and unique cut-off value has not been yet found, its role as a flag of immune system homeostasis is well established. NLR has a well-known prognostic value and independently correlates with mortality in the general population and in several specific subsets of disease (sepsis, pneumonia, COVID-19, cancer, etc.). Moreover, NLR was recently considered as part of the decision-making processes concerning the admission/recovery of patients with COVID-19 pneumonia. This review aims to provide an overview of the main use of this biomarker, focusing on the pathophysiology and the molecular basis underlying its central role as a reliable mirror of inflammatory status and adaptive immunity.

Automated summary

Evaluation of the neutrophil-to-lymphocyte ratio (NLR) as a marker of diseases has become a compelling field of research in the past decade. Although an exact cut-off value has not been determined, NLR is recognized as a marker of immune system homeostasis and is correlated with mortality in general population and specific disease subsets. Additionally, NLR has been considered in decision-making processes for COVID-19 pneumonia patients.