Analysis of comorbidity, demography, clinical characteristics, care pathway and selected investigations as risk factors for severe outcomes (level 2 or 3 admission and/or death) in patients hospitalised with pandemic H1N1 infection during the 2009–2010 pandemic (n=1520)
| Patient characteristic | Cases (severe outcomes), n=268 (17.6%), n (%) | Controls, n=1252 (82.4%), n (%) | Unadjusted OR (95% CI) | p Value |
| Age (years) | ||||
| <1 | 25 (9.3) | 96 (7.7) | 1.87 (1.04 to 3.34) | 0.036 |
| 1–4 | 23 (8.6) | 115 (9.2) | 1.43 (0.80 to 2.58) | 0.231 |
| 5–15 | 29 (10.8) | 192 (15.3) | 1.08 (0.63 to 1.87) | 0.776 |
| 16–24 | 30 (11.2) | 215 (17.2) | 1.00 (reference) | – |
| 25–34 | 44 (16.4) | 198 (15.8) | 1.59 (0.96 to 2.63) | 0.070 |
| 35–44 | 37 (13.8) | 158 (12.6) | 1.68 (0.99 to 2.83) | 0.053 |
| 45–54 | 33 (12.3) | 135 (10.8) | 1.75 (1.02 to 3.00) | 0.042 |
| 55–64 | 30 (11.2) | 85 (6.8) | 2.53 (1.44 to 4.45) | 0.001 |
| ≥65 | 17 (6.3) | 58 (4.6) | 2.10 (1.08 to 4.07) | 0.028 |
| Asthma | 43 (16.0) | 342 (27.3) | 0.51 (0.36 to 0.72) | <0.001 |
| Chronic pulmonary conditions excluding asthma or COPD | 12 (4.5) | 24 (1.9) | 2.40 (1.18 to 4.86) | 0.015 |
| Neurological disorders | 31 (11.6) | 56 (4.5) | 2.79 (1.76 to 4.43) | <0.001 |
| Cardiovascular disease | 50 (18.7) | 138 (11.0) | 1.85 (1.30 to 2.64) | 0.001 |
| Radiological Pneumonia | 94 (35.1) | 160 (12.8) | 3.69 (2.73 to 4.98) | <0.001 |
| C-reactive protein (mg/litre) | ||||
| ≤30 | 38 (14.2) | 355 (28.4) | 1.00 | |
| 31–99 | 41 (15.3) | 221 (17.7) | 1.73 (1.08 to 2.78) | 0.022 |
| ≥100 | 73 (27.2) | 89 (7.1) | 7.66 (4.86 to 12.09) | <0.001 |
| Missing | 116 (43.3) | 587 (46.9) | – | |
| Recorded obese | 17 (6.3) | 32 (2.6) | 2.58 (1.41 to 4.72) | 0.002 |
| Altered consciousness | 40 (14.9) | 34 (2.7) | 6.28 (3.89 to 10.14) | <0.001 |
| Dyspnoea | 141 (52.7) | 434 (34.7) | 2.09 (1.60 to 2.73) | <0.001 |
| Pre-admission antibiotics | 74 (27.6) | 206 (16.5) | 1.94 (1.43 to 2.63) | <0.001 |
| Required supplemental oxygen on admission | 163 (60.8) | 272 (21.7) | 5.59 (4.23 to 7.40) | <0.001 |
| Intravenous fluid replacement on admission | 93 (34.7) | 297 (23.7) | 1.71 (1.29 to 2.27) | <0.001 |
| Delayed admission | ||||
| No | 114 (42.5) | 729 (58.2) | 1.00 | |
| Yes | 47 (17.5) | 180 (14.4) | 1.67 (1.15 to 2.43) | 0.008 |
| Missing | 107 (39.9) | 343 (27.4) | – | |
| Length of hospital stay | ||||
| <2 days | 5 (1.9) | 284 (22.7) | 1.00 | |
| ≥2 days | 170 (63.4) | 875 (69.9) | 11.04 (4.49 to 27.12) | <0.001 |
| Missing | 93 (34.7) | 93 (7.4) | – | |
| In-hospital antibiotic therapy | 235 (87.7) | 1020 (81.5) | 1.62 (1.10 to 2.40) | 0.016 |
No statistically significant association was observed between severe outcomes (level 2 or 3 admission or death) and the following patient characteristics: sex, ethnicity; comorbidities such as chronic obstructive pulmonary disease (COPD), hepatic disease, diabetes, hypertension, immunocompromised status or total comorbidity burden; smoking status, pregnancy, pre-admission antiviral use, oxygen saturation <94% on air; and inpatient treatment with antivirals.