Receiver operating characteristic (ROC) to determine cut-off points of clinical and biomolecular markers to discriminate mortality in severe COVID-19 living at high altitude

Background In 2020, Ecuador had one of the highest death rates because of COVID-19. The role of clinical and biomolecular markers in COVID disease prognosis, is still not well supported by available data. In order for these markers to have practical application in clinical decision-making regarding patient treatment and prognosis, it is necessary to know an optimal cut-off point, taking into consideration ethnic differences and geographic conditions. Aim To determine the value of clinical and biomolecular markers, to predict mortality of patients with severe COVID-19 living at high altitude. Methods In this study, receiver operating characteristic (ROC) curves, area under the curve (AUC) of ROC, sensitivity, specificity and likelihood ratios were calculated to determine levels of clinical and biomolecular markers that best differentiate survivors versus non-survivors in severe COVID subjects that live at a high altitude setting. Results Selected cut-off values for ferritin ([greater than or equal to] 1225 ng/dl, p = 0.026), IL-6 ([greater than or equal to] 11 pg/ml, p = 0.005) and NLR ([greater than or equal to] 22, p = 0.008) at 24 h, as well as PaFiO2 ([less than or equal to] 164 mmHg, p = 0.015), NLR ([greater than or equal to] 16, p = p = 0.013) and SOFA ([greater than or equal to] 6, p = 0.031) at 72 h, appear to have good discriminating power to differentiate survivors versus non-survivors. Additionally, odds ratios for ferritin (OR = 3.38); IL-6 (OR = 17.07); PaFiO2 (OR = 4.61); NLR 24 h (OR = 4.95); NLR 72 h (OR = 4.46), and SOFA (OR = 3.77) indicate increased risk of mortality when cut-off points were taken into consideration. Conclusions We proposed a straightforward and understandable method to identify dichotomized levels of clinical and biomolecular markers that can discriminate between survivors and non-survivors patients with severe COVID-19 living at high altitudes. Keywords: ROC curve, Cut-off, Odds ratio, Severe COVID-19, Inflammatory markers, High altitude