Interleukin-6, Procalcitonin And Neutrophil-To-Lymphocyte Ratio: Potential Immune-Inflammatory Parameters To Identify Severe And Fatal Forms Of Covid-19

Accumulating evidence supports that the viral-induced hyper-inflammatory immune response plays a central role in COVID-19 pathogenesis. It might be involved in the progression to acute respiratory distress syndrome (ARDS), multi-organ failure leading to death. In this study, we aimed to evaluate the prognostic value of the immune-inflammatory biomarkers in COVID-19, then determine optimal thresholds for assessing severe and fatal forms of this disease.153 patients with confirmed COVID-19 were included in this study, and classified into non severe and severe groups. Plasmatic levels of interleukin 6 (IL6), C-reactive protein (CRP), soluble-IL2 receptor (IL2R?), procalcitonin (PCT) and ferritin were measured using chemiluminescence assay. Complete blood count was performed by Convergys 3X? hematology analyzer. Our results demonstrated that the peripheral blood levels of IL6, PCT, CRP, ferritin, IL2R?, white blood cell count (WBC), neutrophil count (NEU), neutrophil-tolymphocyte ratio (NLR), derived neutrophil-to-lymphocyte ratio (d-NLR) were significantly higher in severe forms of COVID-19. The ROC curve analysis showed that IL6 was the most accurate inflammatory biomarker. The calculated cutoff of IL6 (42 pg/ml) could correctly classify > 90% of patients regarding their risk of severity (area under ROC curve (AUROC) = 0.972) and the threshold value of 83 pg/ml was highly predictive of the progression to death (AUROC = 0.94, OR = 184) after a median of 3 days. Besides, IL-6 was positively correlated with other inflammatory markers and the kinetic analysis highlighted its value for monitoring COVID-19 patients. PCT and NLR had also a high prognostic relevance to assess severe forms of COVID-19 with corresponding AUROC of 0.856, 0.831 respectively. Furthermore the cut-off values of PCT (0.16 ng/ml) and NLR (7.4) allowed to predict mortality with high accuracy (se = 96.3%, sp = 70.5%,OR = 61.2)? (se = 75%, sp = 84%, OR = 14.6). The levels of these parameters were not influenced by corticosteroid treatment, which make them potential prognostic markers when patients are already undergoing steroid therapy.