Neutrophil-to-Lymphocyte Ratio and Thrombocyte-to-Lymphocyte Ratio as a Predictor of Severe and Moderate/Mild Acute Respiratory Distress Syndrome Patients: Preliminary Results

Introduction: Acute respiratory distress syndrome (ARDS) represents a major cause of mortality in the intensive care unit (ICU). The inflammatory response is escalated by the cytokines and chemokines released by neutrophils, therefore the search for quantifying the impact of this pathophysiological mechanism is imperative. Neutrophil/lymphocyte ratio (NLR) and platelet/lymphocyte ratio (PLR) are indicators of systemic inflammation, widely accessible, inexpensive, and uncomplicated parameters.
Methods: We conducted a prospective study between March 2023 and June 2023 on patients which presented Berlin criteria for the diagnosis of ARDS during the first 24 hours from admission in the ICU. We included 33 patients who were divided into two groups: one group of 11 patients with severe ARDS and the second group of 22 patients with moderate/mild ARDS. The study evaluated demographic characteristics, leukocyte, lymphocyte, neutrophil, and platelet counts, as well as NLR and PLR values from complete blood count, and severity scores ( APACHE II score and SOFA score). We investigated the correlation of NLR and PLR in the two main groups (severe and moderate/mild acute respiratory distress syndrome patients).
Results: For the NLR ratio statistically significant differences between the the two groups are noted: Severe ARDS 24.29(1.13-96) vs 15.67(1.69-49.71), p=0.02 For the PLR ratio, we obtained significant differences within the group presenting severe ARDS 470.3 (30.83-1427) vs. the group presenting mild/moderate ARDS 252.1 (0-1253). The difference between the two groups is statistically significant (0.049, p<0.05). The cut-off value of NLR resulted to be 23.64, with an Area Under the Curve (AUC) of 0.653 (95% CI: 0.43-0.88). The best cut-off value of PLR was performed to be 435.14, with an Area Under the Curve (AUC) of 0.645 (95% CI: 0.41-0.88).
Conclusion: Our study showed that NLR and PLR ratios 24 hours in patients with moderate/severe ARDS diagnosis can be a good predictor for severity of the disease. These biomarkers could be used in clinical practice due to their convenience, inexpensiveness, and simplicity of parameters. However, further investigations with larger populations of ARDS patients are necessary to support and validate these current findings.