Neutrophil-to-Lymphocyte Ratio and Covid-19

To the Editor:

We read with great interest the article recently published by Tatum et al. (1) entitled “Neutrophil-to-lymphocyte ratio and outcomes in Louisiana COVID-19 patients.” They found that neutrophil-to-lymphocyte ratio (NLR) is a prognostic factor for endotracheal intubation on hospitalization and an independent predictor of mortality risk in SARS-CoV-2 patients. We thank the authors for their valuable contribution to the literature in these difficult conditions. However, we think there are some points that need to be discussed.

The drug use of the patients has not been mentioned in this article and it would be appropriate to mention the use of drugs such as glucocorticoids that may affect the NLR value. As it is known, while the neutrophil count increases with the use of glucocorticoids, other circulating cells such as eosinophils, monocytes, and lymphocytes are reduced (2). This is an indication that it affects NLR values, and it would be more appropriate for the authors to report how many patients were taking corticosteroids.

NLR, one of the routine blood parameters, has been extensively studied in many diseases and remains important (3). Studies have reported that NLR is significantly higher in applications related to infection. Similarly, stress factors such as trauma and gastrointestinal system bleeding may cause increases in NLR (4, 5). Therefore, providing useful information about infection, malignancy, alcohol use, smoking, gastrointestinal bleeding, renal/metabolic conditions, encephalopathy, surgical procedures, and additional medical procedures that may affect NLR values will provide useful information. As a result, NLR can be affected by many factors. The prognostic routine clinical use of these parameters in COVID-19 patients is not yet reasonable. Prospective and multicenter studies are needed.