Usefulness of Selected Peripheral Blood Counts in Predicting Death in Patients with Severe and Critical COVID-19

Background. Immune dysregulation and hypoxemia are two important pathophysiological problems in patients with COVID-19 that affect peripheral blood count parameters. We hypothesized that assessment of the neutrophil–lymphocyte ratio (NLR) and red blood cell distribution width index (RDW-SD) could predict death in patients with severe and critical COVID-19. Methods. Seventy patients admitted to the intensive care unit (ICU) for COVID-19 acute respiratory failure were included in the study. RDW-SD and NLR on the day of ICU admission and peak values during the entire hospitalization were assessed. The primary endpoint was death before ICU discharge. Results. Patients who died had higher NLR on admission (20.3, IQR 15.3–30.2 vs. 11.0, IQR 6.8–16.9; p = 0.003) and higher RDW-SD (48.1 fL; IQR 43.1–50.5 vs. 43.9 fL; IQR 40.9–47.3, p = 0.01) than patients discharged from the ICU. NLR and RDW-SD values on ICU admission accurately predicted death in 76% (AUC = 0.76; 95%CI 0.65–0.86; p = 0.001; cut-off > 14.38) and 72% of cases (AUC = 0.72; 95%CI 0.60–0.82; p = 0.003; cut-off > 44.7 fL), respectively. Multivariable analysis confirmed that NLR > 14.38 on the day of ICU admission was associated with a 12-fold increased risk of death (logOR 12.43; 95%CI 1.61–96.29, p = 0.02), independent of other blood counts, clinical and demographic parameters. Conclusions. Neutrophil–lymphocyte ratio determined on the day of ICU admission may be a useful biomarker predicting death in patients with severe and critical COVID-19.