Blood Urea Nitrogen to Serum Albumin Ratio: A Good Predictor of in-Hospital and 90-Day All-Cause Mortality in AECOPD Patients

Abstract Background: Compared with survivors,previous studies of AECOPD have found that those died in hospital had higher blood urea nitrogen levels and poorer nutritional status.Nevertheless,the association between blood urea nitrogen to serum albumin ratio (BUN/ALB ratio) and in-hospital and short-term prognosis in AECOPD patients remains unclear.The aim of this study was to explore the usefulness of BUN/ALB ratio in AECOPD as an objective predictor for in-hospital and 90-day all-cause mortality.Methods: BUN/ALB ratio levels were measured in AECOPD patients on admission.By drawing the ROC curve of the patients,we obtained the cut-point of the BUN/ALB ratio level for in-hospital death.Multivariate logistic regression was used for analyses of the factors of in-hospital mortality and multivariate Cox regression was used to analyse the factors of 90-day all-cause mortality.Results: A total of 362 patients were recruited and 319 patients were finally analyzed,23 patients died during hospitalization and the fatality rate was 7.2%. Furthermore,14 patients died during 90-day follow-up.Compared with those in-hospital survivors,patients who died in hospital were older(80.78±6.58vs.75.09±9.73 years old, P =0.001),had a higher percentage of congestive heart failure(69.6% vs.27.4%, P<0.001),had higher BUN/ALB ratio levels(0.329(0.250,0.399)vs.0.145(0.111,0.210), P<0.001),had higher neutrophil counts(10.27(7.21，14.04)vs.6.58(4.58，9.04), P<0.001),higher blood urea nitrogen levels(10.86(7.10,12.25) vs.5.35(4.14,7.40), P<0.001),a lower albumin level(32.58±3.72vs.36.26±4.53, P<0.001) and had a lower lymphocyte count(0.85(0.58,1.21) vs.1.22(0.86,1.72), P=0.001).The ROC curve showed that the area under the curve (AUC) of BUN/ALB ratio for in-hospital death was 0.87, (95%CI: 0.81-0.93, P< 0.001), the best cut-point value to discriminate survivors from nonsurvivors in hospital was 0.249, the sensitivity was 78.3%, the specificity was 86.5%, and the youden’s index was 0.648.Having an BUN/ALB ratio ≥0.249 was an independent risk factor for both in-hospital and 90-day all-cause mortality after adjustment for relative risk(RR)(RR=15.08,95% CI:3.80-59.78, P< 0.001 for the multivariate logistic regression analysis) and hazard ratio (HR)(HR=5.34,95% CI:1.62-17.57, P=0.006 for the multivariate cox regression analysis).Conclusion: An elevated BUN/ALB ratio level was a strong and independent predictor of in-hospital and 90-day all-cause mortality in AECOPD patients.