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

Table 4 Univariate and multivariate logistic regression analyses of factors affecting in-hospital mortality

Variable	Univariate analysis		Multivariate analysis
Variable	RR (95% CI)	P value	RR (95% CI)	P value
Age (per increase of 5-year)	1.47 (1.11–1.96)	0.008	0.95 (0.60–1.51)	0.836
BMI (per increase of 1 point)	0.94 (0.84–1.05)	0.243	0.90 (0.76–1.06)	0.201
Sex (female vs. male)	0.60 (0.23–1.61)	0.312	0.35 (0.05–2.19)	0.259
Smoking status (never smoker vs. current/ever smoker)	1.23 (0.41–3.76)	0.713	3.09 (0.40–23.70)	0.277
Exacerbations during preceding year (yes vs. no)	2.50 (1.03–6.07)	0.044	2.93 (0.74–11.59)	0.127
GOLD stage (per increase to next stage)	0.87 (0.52–1.45)	0.590
CHF (yes vs. no)	6.07 (2.41–15.29)	< 0.001	4.36 (1.07–17.85)	0.040
RD (yes vs. no)	0.85 (0.36–1.99)	0.701	0.32 (0.09–1.13)	0.076
Bronchiectasis (yes vs. no)	0.47 (0.16–1.43)	0.186
Diabetes (yes vs. no)	0.84 (0.19–3.78)	0.825
Hypertension (yes vs. no)	1.06 (0.45–2.50)	0.893
CHD (yes vs. no)	1.54 (0.63–3.79)	0.343
Neutrophil count(per increase of 1 × 10⁹/L)	1.16 (1.08–1.24)	< 0.001	1.15 (1.02–1.30)	0.020
Lymphocyte count(per increase of 1 × 10⁹/L)	0.24 (0.09–0.59)	0.002	0.36 (0.09–1.47)	0.154
PH
(PH < 7.35 vs. 7.35 ≤ PH ≤ 7.45)	5.08 (1.78–14.48)	0.002	8.87 (1.62–48.55)	0.012
(PH > 7.45 vs. 7.35 ≤ PH ≤ 7.45)	7.31 (2.51–21.32)	< 0.001	4.04 (0.87–18.81)	0.075
PaO₂ (≥ 60 vs. < 60 mmHg)	4.56 (1.51–13.77)	0.007	4.86 (0.89–26.67)	0.069
PaCO₂ (≥ 50 vs. < 50 mmHg)	1.88 (0.74–4.77)	0.187
BUN/ALB ratio (≥ 0.249 vs. < 0.249)	22.39 (7.88–63.62)	< 0.001	15.08 (3.80–59.78)	< 0.001

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