Blood Urea Nitrogen to Serum Albumin Ratio: A Good Predictor of In-Hospital and 90-Day All-Cause Mortality in Patients With Acute Exacerbations of Chronic Obstructive Pulmonary Disease

Zixiong Zeng; Xiaocui Ke; Shan Gong; Xin Huang; Qin Liu; Xiaoying Huang; Juan Cheng; Yuqun Li; Liping Wei


BMC Pulm Med. 2022;22(476) 

In This Article

Abstract and Introduction


Background: Previous studies on acute exacerbation of chronic obstructive pulmonary disease (AECOPD) have found that those who died in hospital had higher blood urea nitrogen levels and a worse nutritional status compared to survivors. However, the association between the blood urea nitrogen to serum albumin ratio (BUN/ALB ratio) and in-hospital and short-term prognosis in patients with AECOPD 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: We recorded the laboratory and clinical data in patients with AECOPD on admission. By drawing the ROC curve for the patients, we obtained the cut-off point for the BUN/ALB ratio 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 analyze the factors of 90-day all-cause mortality.

Results: A total of 362 patients were recruited and 319 patients were finally analyzed. Twenty-three patients died during hospitalization and the fatality rate was 7.2%. Furthermore, 14 patients died by the 90-day follow-up. Compared with in-hospital survivors, patients who died in hospital were older (80.78 ± 6.58 vs. 75.09 ± 9.73 years old, P = 0.001), had a higher prevalence of congestive heart failure(69.6% vs. 27.4%, P < 0.001), had a higher BUN/ALB ratio [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 ± 3.72 vs. 36.26 ± 4.53, P < 0.001) and 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-off point value to discriminate survivors from non-survivors in hospital was 0.249, the sensitivity was 78.3%, the specificity was 86.5%, and Youden's index was 0.648. Having a 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 a multivariate logistic regression analysis) and hazard ratio (HR; HR = 5.34, 95% CI 1.62–17.57, P = 0.006 for a multivariate Cox regression analysis).

Conclusion: An elevated BUN/ALB ratio was a strong and independent predictor of in-hospital and 90-day all-cause mortality in patients with AECOPD.


Chronic obstructive pulmonary disease (COPD), a complex multi-component disease with chronic systemic inflammation, is a common cause of death around the world.[1,2] Acute exacerbations in COPD (AECOPD) are key events and they negatively influence the health status of patients, rates of hospitalization, readmission, and disease progression.[3,4] However, effective methods to identify hospitalized patients with AECOPD with poor outcomes are still lacking. It is vital for clinicians to pay more attention to evaluating the severity and prognosis of patients with AECOPD in advance. Some severity scoring systems had been developed to assist with predicting the outcomes for AECOPD, such as the APACHE II score, DECAF score and SAPS II score.[5–7] Although these scoring systems have shown great potential for accurately predicting AECOPD prognoses,[6,8,9] not all patients cooperate with clinicians' investigations; for example, patients with dementia or the elderly. In addition, the subjectivity of some clinicians may affect the scoring system.[10]

Based on previous studies, many blood biomarkers have been reported to predict the prognoses and indicate the severity of AECOPD, such as C-reactive protein and procalcitonin.[11,12] Previous studies have found that non-survivors had higher blood urea nitrogen (BUN) levels and poorer nutritional status than survivors.[13–15] Therefore, we hypothesized that patients with AECOPD with a higher BUN/ALB ratio have an inverse relationship with poorer outcomes of COPD exacerbation. However, to our knowledge, there is no study that has explored the association between BUN/ALB ratio and in-hospital mortality and the short-term prognosis in patients with AECOPD. Accordingly, the objective of our study was to ascertain the prognostic role of BUN/ALB ratio for in-hospital and 90-day all-cause mortality in AECOPD.