Neutrophil-Lymphocyte Ratio Predicting Case Severity in SARS-CoV-2 Infection: A Review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly contagious and has taken an enormous toll on the worldwide quality of life and the global economy, in addition to the lives lost due to coronavirus disease 2019 (COVID-19). Precautionary measures and timely identification of the infected cases are essential to minimize the spread of SARS-CoV-2. Infection with this virus causes a spike in the proinflammatory cytokines, resulting in immune system-mediated host tissue damage, thus leading to mortality. Therefore, identifying mild, moderate, and severe cases is crucial to rendering appropriate care. Recent research has focused on identifying laboratory techniques to predict the case severity and outcome of COVID-19 cases. Low serum lymphocyte levels, low lymphocyte-to-C-reactive protein ratio, low platelet-to-lymphocyte ratio, thrombocytopenia, and high neutrophil-lymphocyte ratio (NLR) have been observed in critical infections. NLR might be a prognostic marker for disease severity. Severe cases can be triaged at hospital admission for proper treatment planning and to reduce mortality. This review highlights the potential role of NLR hematological assay in SARS-CoV-2 infection and the mechanism of neutrophilic-induced host tissue damage.