The Impact of Serum Albumin Levels on COVID-19 Mortality

Low serum albumin (SA) correlates with mortality in critically ill patients, including those with COVID-19. We aimed to identify SA thresholds to predict the risk of longer hospital stay, severe respiratory failure, and death in hospitalized adult patients with COVID-19 pneumonia. A prospective longitudinal study was conducted at the Infectious Diseases Unit of Trieste University Hospital (Italy) between March 2020 and June 2021. The evaluated outcomes were: (1) need of invasive mechanical ventilation (IMV); (2) length of hospital stay (LOS); and (3) 90-day mortality rate. We enrolled 864 patients. Hypoalbuminemia (<3.5 g/dL) was detected in 586 patients (67.8%). SA on admission was significantly lower in patients who underwent IMV (2.9 vs. 3.4 g/dL; p < 0.001). The optimal SA cutoff predicting the need of IMV was 3.17 g/dL (AUC 0.688; 95% CI: 0.618-0.759; p < 0.001) and this threshold appeared as an independent risk factor for the risk of IMV in multivariate Cox regression analysis. The median LOS was 12 days and a higher SA was predictive for a shorter LOS (p < 0.001). The overall 90-day mortality rate was 15%. SA was significantly lower in patients who died within 90 days from hospital admission (3.1 g/dL; IQR 2.8-3.4; p < 0.001) as compared to those who survived (3.4 g/dL; IQR 3.1-3.7). The optimal SA threshold predicting high risk of 90-day mortality was 3.23 g/dL (AUC 0.678; 95% CI: 0.629-0.734; p < 0.001). In a multivariate Cox regression analysis, SA of <3.23 g/dL appeared to be an independent risk factor for 90-day mortality. Our results suggest that low SA on admission may identify patients with COVID-19 pneumonia at higher risk of severe respiratory failure, death, and longer LOS. Clinicians could consider 3.2 g/dL as a prognostic threshold for both IMV and mortality in hospitalized COVID-19 patients.