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Table 3 Ordinary, marginal and multilevel logistic regression results: Odds ratios, OR, describing associations with 30-day mortality for patient-level and hospital-level characteristics

From: Hospital-level associations with 30-day patient mortality after cardiac surgery: a tutorial on the application and interpretation of marginal and multilevel logistic regression

Risk factor Ordinary Marginal Multilevel*
  OR 95% CI OR 95% CI OR 95% CI
Patient-level       
Age group (< 60 y, reference group):       
60-70 y 1.5 (1.2,2.0) 1.5 (1.2-1.8) 1.5 (1.2,2.0)
70-80 y 2.7 (2.1,3.4) 2.4 (2.0-3.0) 2.7 (2.1,3.3)
80+y 3.6 (2.8,4.8) 3.3 (2.7-4.5) 3.7 (2.8,4.9)
Gender (female vs. male) 1.3 (1.1,1.6) 1.3 (1.1-1.5) 1.3 (1.1,1.6)
NYHA Class (I&II, reference group):       
III 1.3 (1.1,1.6) 1.3 (1.1-1.6) 1.4 (1.1,1.6)
IV 1.7 (1.4,2.1) 1.6 (1.3-2.0) 1.7 (1.4,2.2)
Urgency of procedure (elective, reference group):       
Urgent 2.0 (1.6,2.4) 1.8 (1.5-2.2) 2.0 (1.6,2.4)
Emergency/salvage 5.4 (4.3,7.0) 4.9 (4.0-6.0) 5.5 (4.3,7.0)
Ejection fraction estimate (Mild, > 45%, reference group):       
Moderate (30-45%) 1.4 (1.2,1.8) 1.3 (3.0-1.6) 1.4 (1.2,1.8)
Severe (< 30%) 2.3 (1.8,2.9) 2.2 (1.8-2.7) 2.3 (1.8,2.9)
Hypercholesterolaemia 1.0 (0.8, 1.1) 1.0 (0.8-1.1) 1.0 (0.8,1.2)
Preoperative dialysis 2.2 (1.5,3.2) 2.2 (1.5-3.0) 2.2 (1.5,3.2)
Previous cardiac surgery 1.6 (1.3,2.0) 1.6 (1.3-2.0) 1.7 (1.3,2.0)
Procedure type (CABG, reference group):       
Valve(s) 1.7 (1.3, 2.2) 1.6 (1.2-2.0) 1.7 (1.3, 2.2)
Valve(s)+CABG 2.2 (1.8, 2.8) 2.0 (1.6-2.6) 2.2 (1.8, 2.8)
Other 3.4 (2.7,4.1) 3.0 (2.4-3.7) 3.4 (2.8,4.2)
Inotropic medication 3.1 (2.4,3.9) 3.0 (2.4-3.7) 3.2 (2.5,4.1)
Peripheral vascular disease 1.7 (1.4,2.1) 1.6 (1.3-2.0) 1.7 (1.4,2.0)
Body mass index (25+ vs. < 25 kg/m 2 ) 0.8 (0.7,1.0) 0.9 (0.7-1.0) 0.8 (0.7,1.0)
Hospital-level       
Academic affiliation (teaching vs. non-teaching) 1.2 (0.9,1.7) 1.2 (0.9-1.5) 1.3 (0.8,1.9)
Median of the annual number of cardiac surgeries 2001-2009, per 100 surgeries 0.88 (0.83,0.94) 0.93 (0.9-1.0) 0.91 (0.82,1.1)
  1. *The estimated hospital-level variance, τ2, was 0.04.
  2. *The estimated hospital-level variance, τ2, was 0.04