Multivariate analysis of variables associated with H1N1 influenza-related pneumonia
| Characteristic | Odds ratio | 95% CI | p Value |
| Age ≤65 years | 12.7 | 7.2 to 22.2 | <0.001 |
| White cell count ≤12×109/l | 9.7 | 6.1 to 15.6 | <0.001 |
| Bilateral radiographic change | 3.3 | 2.1 to 5.4 | <0.001 |
| Oriented in time/place/person | 2.6 | 1.2 to 5.3 | 0.012 |
| Temperature ≥38°C | 1.9 | 1.3 to 3.0 | 0.003 |
| Female sex | 1.4 | 0.9 to 2.2 | 0.09 |
| Urea <7 mmol/l | 1.4 | 0.8 to 2.3 | 0.214 |
Complete data on all seven variables were available in 205 patients in the H1N1 cohort and 642 patients in the community-acquired pneumonia cohort.