Blood urea nitrogen to serum albumin ratio independently predicts mortality and severity of community-acquired pneumonia

Motoi Ugajin, Kenichi Yamaki, Natsuko Iwamura, Takeo Yagi, Takayuki Asano

Department of Respiratory Medicine, Ichinomiya-Nishi Hospital, Ichinomiya City, Aichi Prefecture, Japan

Background: Early studies of community-acquired pneumonia showed that nonsurvivors had higher blood urea nitrogen levels and lower serum albumin levels than survivors. Therefore, elevation of the blood urea nitrogen to serum albumin (B/A) ratio may identify patients with community-acquired pneumonia who are becoming critically ill. This study investigated the correlation between commonly used laboratory markers, in particular the B/A ratio, and clinical outcomes of community-acquired pneumonia.
Methods: This observational study was performed in consecutive patients with community-acquired pneumonia admitted to our hospital over a period of one year. Blood counts, commonly used laboratory markers, microbiological tests, and calculation of Pneumonia Severity Index (PSI) and CURB-65 were done on admission. The endpoints were mortality within 28 days of admission and requirement for intensive care.
Results: One hundred and seventy-five patients with community-acquired pneumonia were enrolled. Nineteen patients died within 28 days of admission and 29 patients required intensive care. Using multivariate analysis, independent factors associated with mortality were the requirement for intensive care (odds ratio [OR] 14.96, 95% confidence interval [CI] 3.73–60.03, P < 0.001), PSI class (OR 3.55, 95% CI 1.08–11.66, P = 0.037), and B/A ratio (OR 1.10, 95% CI 1.01–1.20, P = 0.037). Similarly, independent factors associated with need for intensive care were PSI class (OR 5.35, 95% CI 1.90–15.06, P = 0.002), CURB-65 (OR 2.37, 95% CI 1.26–4.45, P = 0.007), and B/A ratio (OR 1.27, 95% CI 1.09–1.47, P = 0.002).
Conclusion: The B/A ratio is a simple but independent predictor of mortality and severity of community-acquired pneumonia.

Keywords: blood urea nitrogen to serum albumin ratio, Pneumonia Severity Index, CURB-65, community-acquired pneumonia, mortality, severity