| Clinical feature | No | CPE/Emp (%) | Uncomplicated pneumonia (%) | AOR (95% CI) | p Value |
| Albumin <30 g/l | 144 | 38.0 | 9.3 | 4.55 (2.45 to 8.45) | <0.0001 |
| CRP >100 mg/l | 948 | 97.8 | 72.9 | 15.7 (3.69 to 66.9) | 0.0002 |
| Platelet count >400×109/l | 157 | 31.5 | 10.9 | 4.09 (2.21 to 7.54) | <0.0001 |
| Sodium <130 mmol/l | 105 | 19.6 | 7.4 | 2.70 (1.55 to 4.70) | 0.0005 |
| Intravenous drug use | 38 | 10.9 | 2.4 | 2.82 (1.09 to 7.30) | 0.03 |
| Chronic alcohol abuse | 70 | 13 | 4.9 | 4.28 (1.87 to 9.82) | 0.0006 |
| COPD | 257 | 4.3 | 21.5 | 0.18 (0.06 to 0.53) | 0.002 |
AOR, adjusted odds ratio; COPD, chronic obstructive pulmonary disease; CPE/Emp, complicated parapneumonic effusion or empyema; CRP, C-reactive protein.