Diagnostic Value of C-Reactive Protein, Albumin, and the CRP-to-Albumin Ratio for Predicting Mortality in Hospitalized Patients with COVID-19 in Brazilian Hospitals

Background: In recent years, studies have been conducted to understand the immuno-inflammatory changes related to COVID-19. Different serum biomarkers have been extensively investigated as diagnostic and/or prognostic markers of various clinical outcomes. Objective: To evaluate the diagnostic value of serum C-reactive protein (CRP) and albumin levels, and the CRP-to-albumin ratio, determined on hospital admission, for predicting mortality in patients with COVID-19. Methods: A retrospective cohort study of patients hospitalized with COVID-19 from March to August 2020 in two reference hospitals, one public and one private, in the Central Region of Brazil. The most important laboratory data included serum C-reactive protein (CRP) and albumin concentrations determined on hospital admission. The prognostic value of each biomarker for predicting patient mortality was analyzed using the receiver operating characteristic (ROC) curve. Results: A total of 128 patients were hospitalized with COVID-19 during the study period, of whom 70 (54.7%) were male, with a mean age of 51.4 years. The mean (standard deviation [SD]) CRP concentration in patients who died was 152.1 (108.2) mg/dL, which was higher than that in survivors (p=0.007). The mean (SD) albumin concentration was 3.0 (0.6) g/dL among patients who died, which was lower than that in survivors (p=0.004). The mean [SD] CRP-to-albumin ratio was significantly higher among patients who died than among survivors (54.8 [32.8] vs. 34.8 [43.9]; p=0.002). ROC curves showed a higher diagnostic accuracy (69%) for the CRP-to-albumin ratio than for CRP or albumin alone. Analysis of different cut-off points for this ratio showed sensitivities ranging from 71.4% to 92.9%. These results confirm previous observations that CRP, albumin and CRP-to-albumin ratio are associated with serious outcomes from COVID-19 and their measurement at hospital admission identifies patients with a worse prognosis of the disease. Conclusions: Serum concentrations of CRP and albumin and the CRP-to-albumin ratio determined on hospital admission are accurate biomarkers with good sensitivity for predicting mortality among hospitalized patients with COVID-19.