The blood urea nitrogen-to-creatinine ratio is associated with acute kidney injury among COVID-19 patients

Introduction: To explore the associations between the blood urea nitrogen-to-creatinine ratio (BCR), acute kidney injury (AKI), and in-hospital mortality in coronavirus disease 2019 (COVID-19) patients. Methods: COVID-19 patients from Ruijin Hospital LuWan Branch, Shanghai Jiao Tong University School of Medicine were enrolled in this study. Clinical data and laboratory parameters were collected. AKI was defined using two serum creatinine tests according to KDIGO guidelines. Cox regression and receiver operating characteristic (ROC) curve analyses were performed. Results: Five hundred and sixty-seven COVID-19 patients were enrolled, 44.1% of whom were male. The mean age was 75 years. Among all patients, 17 patients developed AKI, and 30 patients died during hospitalization. Compared to non-AKI patients, the BCR in AKI patients was significantly greater. BCR was significantly associated with AKI (unadjusted HR 1.04, 95% CI: 1.02-1.05, p < 0.001; adjusted HR 1.06, 95% CI 1.02-1.10, p = 0.001). BCR was also a risk factor of in-hospital mortality (unadjusted HR 1.03, 95% CI: 1.02-1.05, p < 0.001; adjusted HR 1.04, 95% CI: 1.01-1.08, p = 0.019). The BCR threshold was 38.9, with 70.6% sensitivity and 87.1% specificity for predicting AKI, while a threshold of 33.0 predicted mortality. Subgroup analysis revealed that BCR could predict AKI and mortality in different subgroups according to sex, age, diabetes mellitus, and estimated glomerular filtration rate. Conclusions: The BCR, a simple index, is associated with AKI onset and mortality in COVID-19 patients. The BCR possesses certain specificity for AKI screening, which indicates an effective clinical indicator for screening patients at high risk of AKI.