Inflammatory biomarkers as predictors of intubation and mortality in severe COVID-19

Abstract

<b>Introduction:</b> Biomarkers may be useful to predict which patients may have higher risk of bad outcomes such as invasive mechanical ventilation (IMV) or mortality. <b>Objective:</b> To evaluate the association of serum IL-6 and other biomarkers as predictors of IMV and mortality in severe COVID-19. <b>Methods:</b> Cohort study of severe COVID-19 patients (SARS-CoV2 RT-PCR positive test). IL-6, procalcitonin, and C reactive protein were measured in all patients within 96 hours after hospital admission. The primary outcomes were the start of IMV and death. <b>Results:</b> 89 subjects were included, with a total mortality of 22%, and 67 (75.2%) subjects required IMV. Patients that required IMV had higher levels of IL-6 compared to subjects without IMV (580.03 pg/ml vs 70.71pg/ml; p.0005). Oher variables associated with IMV were fever during the first five days after admission (OR: 37.61, 95% CI; 2.61-542: p 0.008). After a ROC curve analysis, we set up a cutoff value of IL-6 of 282 pg/ml that had a strong association with IMV (OR 10.8; CI 95%, 1.56-75.4: p 0.02). Procalcitonin was also strongly associated with IMV (OR 234.5; CI 95%, 2.49-21998: p 0.02) with an AUROC of 0.86.&nbsp; In the regressive logistic analysis IL-6 lost association strength, resulting in non-significant mortality. The protective factor observed for mortality was the recovery of lymphocytes in the first five days of hospitalization with an adjusted OR of 0.09 (CI 95%, 0.002-0.19; p 0.0001). <b>Conclusions:</b> IL-6 serum levels and procalcitonin were independently associated with IMV. These findings suggest that the serial measurement of this biomarkers play an important role in the timely identification of respiratory failure in severe COVID-19.