Univariate association between selected clinical characteristics and presence of H1N1 infection
| Characteristic | H1N1 cohort | CAP cohort | OR | 95% CI | p Value |
| Age ≤65 years | 228/254 | 200/648 | 19.6 | 12.7 to 30.3 | <0.001 |
| White cell count ≤12×109/l | 189/239 | 222/646 | 7.2 | 5.1 to 10.3 | <0.001 |
| Oriented in time/place/person | 236/254 | 466/648 | 5.1 | 3.1 to 8.5 | <0.001 |
| Urea <7 mmol/l | 175/232 | 270/647 | 4.3 | 3.1 to 6.0 | <0.001 |
| Temperature ≥38°C | 142/245 | 232/644 | 2.5 | 1.8 to 3.3 | <0.001 |
| Bilateral x-ray change | 89/228 | 129/648 | 2.6 | 1.9 to 3.6 | <0.001 |
| CRP ≤50 mg/l | 67/184 | 126/602 | 2.2 | 1.5 to 3.1 | <0.001 |
| Albumin ≤30 g/dl | 44/177 | 189/488 | 1.9 | 1.3 to 2.8 | 0.001 |
| Female sex | 145/254 | 281/648 | 1.7 | 1.3 to 2.3 | 0.001 |
| Pulse ≥125/min | 45/244 | 107/646 | 1.1 | 0.8 to 1.7 | 0.51 |
CAP, community-acquired pneumonia; CRP, C-reactive protein.