Prognostic role of Interleukin-6/lymphocytes ratio in SARS-CoV2 related pneumonia

Abstract

Introduction and aim: Interleukin-6 to lymphocyte (IL-6/Lym) ratio has been identified as a potential prognostic tool in patients with SARS-CoV2 related pneumonia. The aim of our study was to compare the prognostic power of IL-6/Lym ratio with other biomarkers in patients initially admitted in a non intensive unit and suffering for respiratory failure associated with SARS-CoV2 related pneumonia.

Materials and methods: IL-6/Lym ratio, IL-6, D-Dimer, D-Dimer/fibrinogen ratio, fibrinogen, C-reactive protein (CRP), lymphocytes count and neutrophil/lymphocyte (N/L) ratio collected at hospital admission were tested as prognosticators of negative outcome, defined as combined endpoint in-hospital mortality and/or Intensive Care Unit (ICU) admission requiring oro-tracheal intubation (OTI).

Results: Study population encompassed two hundreds and twenty-three patients (46% females) with mean age ± DS 69.4 ± 13.3 years. Eighty-nine patients (39.9%) suffered for severe respiratory failure and required non invasive ventilation, helmets and/or high flow nasal cannula. Fourty-one patients (18.3%) died during hospital stay and/or required OTI. In these patients mean values of IL-6/Lym ratio, IL-6, CRP and N/L were significantly higher and lymphocytes count was significantly lower compared with patients discharged alive and/or not requiring OTI, while no difference was found in mean values of D-Dimer, D-Dimer/Fibrinogen ratio and fibrinogen. AUC (0.797, 95% CI: 0.738-0.848) of IL-6/Lym ratio was the highest compared with those of all the other analyzed biomarkers and the difference was significant with the exception of IL-6. At multivariate logistic regression IL-6/Lym ratio > 66.5 resulted the only independent biomarker associated with mortality and/or OTI (OR 5.65; 95% 1.63-19.54).

Conclusion: IL-6/Lym ratio seems to be an optimal prognosticator in SARS-CoV2 related pneumonia. Its routinary use in COVID-19 patients could be warranted.

Keywords: COVID-19; Cytokine storm; Interleukin-6; Lymphocytes; Prognosis; SARS-CoV2.