Elevated BUN Upon Admission as a Predictor of in-Hospital Mortality Among Patients with Acute Exacerbation of COPD: A Secondary Analysis of Multicenter Cohort Study

BACKGROUND: High blood urea nitrogen (BUN) is observed in a subset of patients with acute exacerbation of COPD (AECOPD) and may be linked to clinical outcome, but findings from previous studies have been inconsistent. METHODS: We performed a retrospective analysis of patients prospectively enrolled in the MAGNET AECOPD Registry study (ChiCTR2100044625). Receiver operating characteristic (ROC) was used to determine the level of BUN that discriminated survivors and non-survivors. Univariate and multivariate Cox proportional hazards regression analyses were performed to assess the impact of BUN on adverse outcomes. RESULTS: Overall, 13,431 consecutive inpatients with AECOPD were included in this study, of whom 173 died, with the mortality of 1.29%. The non-survivors had higher levels of BUN compared with the survivors [9.5 (6.8–15.3) vs 5.6 (4.3–7.5) mmol/L, P < 0.001]. ROC curve analysis showed that the optimal cutoff of BUN level was 7.30 mmol/L for in-hospital mortality (AUC: 0.782; 95% CI: 0.748–0.816; P < 0.001). After multivariate analysis, BUN level ≥7.3 mmol/L was an independent risk factor for in-hospital mortality (HR = 2.099; 95% CI: 1.378–3.197, P = 0.001), also for invasive mechanical ventilation (HR = 1.540; 95% CI: 1.199–1.977, P = 0.001) and intensive care unit admission (HR = 1.344; 95% CI: 1.117–1.617, P = 0.002). Other independent prognostic factors for in-hospital mortality including age, renal dysfunction, heart failure, diastolic blood pressure, pulse rate, PaCO2 and D-dimer. CONCLUSION: BUN is an independent risk factor for in-hospital mortality in inpatients with AECOPD and may be used to identify serious (or severe) patients and guide the management of AECOPD. CLINICAL TRIAL REGISTRATION: MAGNET AECOPD; Chinese Clinical Trail Registry NO.: ChiCTR2100044625; Registered March 2021, URL: http://www.chictr.org.cn/showproj.aspx?proj=121626.