Background The clinical presentation of COVID‐19 ranges from a mild, self‐limiting disease, to multiple organ failure and death. Most severe COVID‐19 cases present low lymphocytes counts and high leukocytes counts, and accumulated evidence suggests that in a subgroup of patients presenting severe COVID‐19, there may be a hyperinflammatory response driving a severe hypercytokinaemia which may be, at least in part, signalling the presence of an underlying endothelial dysfunction. In this context, available data suggest a prognostic role of neutrophil‐lymphocyte ratio (NLR) in various inflammatory diseases and oncological processes. Following this rationale, we hypothesized that NLR, as a marker of endothelial dysfunction, may be useful in identifying patients with a poor prognosis in hospitalized COVID‐19 cases. Design A retrospective observational study performed at Hospital Universitario HM Puerta del Sur, Madrid, Spain, which included 119 patients with COVID‐19 from 1 March to 31 March 2020. Patients were categorized according to WHO R&D Expert Group. Results Forty‐five (12.1%) patients experienced severe acute respiratory failure requiring respiratory support. Forty‐seven (12.6%) patients died. Those with worse outcomes were older (P = .002) and presented significantly higher NLR at admission (P = .001), greater increase in Peak NLR (P < .001) and higher increasing speed of NLR (P = .003) compared with follow‐up patients. In a multivariable logistic regression, age, cardiovascular disease and C‐reactive protein at admission and Peak NLR were significantly associated with death. Conclusions NLR is an easily measurable, available, cost‐effective and reliable parameter, which continuous monitoring could be useful for the diagnosis and treatment of COVID‐19.

The clinical impact of COVID-19 disease calls for the identification of routine variables to identify patients at increased risk of death. Current understanding of moderate-to-severe COVID-19 pathophysiology points toward an underlying cytokine release driving a hyperinflammatory and procoagulant state. In this scenario, white blood cells and platelets play a direct role as effectors of such inflammation and thrombotic response. We investigate whether hemogram-derived ratios such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio and the systemic immune-inflammation index may help to identify patients at risk of fatal outcomes. Activated platelets and neutrophils may be playing a decisive role during the thromboinflammatory phase of COVID-19 so, in addition, we introduce and validate a novel marker, the neutrophil-to-platelet ratio (NPR).Two thousand and eighty-eight hospitalized patients with COVID-19 admitted at any of the hospitals of HM Hospitales group in Spain, from March 1 to June 10, 2020, were categorized according to the primary outcome of in-hospital death.Baseline values, as well as the rate of increase of the four ratios analyzed were significantly higher at hospital admission in patients who died than in those who were discharged (p<0.0001). In multivariable logistic regression models, NLR (OR 1.05; 95% CI 1.02 to 1.08, p=0.00035) and NPR (OR 1.23; 95% CI 1.12 to 1.36, p<0.0001) were significantly and independently associated with in-hospital mortality.According to our results, hemogram-derived ratios obtained at hospital admission, as well as the rate of change during hospitalization, may easily detect, primarily using NLR and the novel NPR, patients with COVID-19 at high risk of in-hospital mortality.