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Table 1 Patient characteristics and in-hospital mortality overall and by hospital case volume level for discharges with a principal diagnosis of pneumonia, Japanese DPC database, 2010

From: Association between hospital case volume and mortality in non-elderly pneumonia patients stratified by severity: a retrospective cohort study

  Total Very low (≤7) Low (8–11) Medium (12–17) High (≥18) p
Number of patients 8293 1771 2020 2146 2356  
Sex (male, %) 57.6% 59.7% 59.3% 55.5% 56.4% 0.01
Age       0.11
 18–44 years 37.9% 36.8% 36.5% 40.5% 37.4%  
 45–54 years 15.7% 15.3% 15.6% 15.5% 16.3%  
 55–64 years 46.4% 47.9% 47.8% 44.0% 46.3%  
Charlson comorbidity index       0.16
 0 43.9% 44.0% 42.2% 43.1% 46.1%  
 1 or 2 42.8% 42.3% 43.3% 43.2% 42.2%  
 3–6 11.1% 11.2% 12.0% 11.4% 10.0%  
 7 and above 2.2% 2.6% 2.4% 2.2% 1.7%  
Referred from clinics/other hospitals 36.9% 36.0% 35.6% 42.4% 33.5% <.001
Severity Indices       
 BUN ≥21 mg/dL or signs of dehydration 19.8% 22.7% 19.7% 19.3% 18.4% 0.01
 SpO2 ≤ 90% (or ≤ PaO2 60 Torr) 22.1% 21.0% 22.7% 21.9% 22.5% 0.60
 Presence of cognitive disturbance 8.0% 8.0% 8.0% 8.4% 7.6% 0.79
 Systolic blood pressure ≤90 mmHg 7.6% 9.3% 8.2% 7.1% 6.4% 0.004
Academic hospital 12.1% 11.5% 14.9% 11.1% 10.9% <.001
In-hospital death 3.3% 3.8% 3.6% 3.4% 2.6% 0.14
  1. p-value from chi-squared test for independence.
  2. BUN: blood urea nitrogen; SpO2: oxygen saturation; PaO2: arterial oxygen tension.