Basic characteristics of the 336 patients categorised by 30-day mortality
| All | Survivor | Non-survivor | P value | |
| n=336 | n=264 | n=72 | ||
| Demographic data | ||||
| Age (years) | 61(53-69) | 62 (55.8–72.3) | 61 (51–69) | 0.09 |
| Sex | 211 (62.8%) | 164 (62.1%) | 47 (65.3%) | 0.68 |
| Body mass index | 24.5 (21.5–27.7) | 24.33 (21.4–26.2) | 24.71 (21.6–28.2) | 0.01 |
| Disease severity | ||||
| APACHE II | 22 (17–29) | 28 (22.0–35.0) | 21 (15–27) | <0.01 |
| PSI | 118 (88–151) | 146.5 (123.0–172.5) | 108 (80–140) | <0.01 |
| PaO2/FiO2 | 107 (65–159.2) | 85.9 (55.4–130.4) | 111.2 (68–174) | <0.01 |
| Comorbidities | ||||
| Malignancy | 50 (14.9%) | 37 (14%) | 13 (18.1%) | 0.45 |
| Congestive heart failure | 37 (11%) | 27 (10.2%) | 10 (13.9%) | 0.40 |
| Diabetes mellitus type 2 | 102 (30.4%) | 78 (29.5%) | 24 (33.3%) | 0.56 |
| Chronic pulmonary diseases | 31 (9.2%) | 25 (9.5%) | 6 (8.3%) | 0.99 |
| Chronic renal failure | 24 (7.1%) | 18 (6.8%) | 6 (8.3%) | 0.61 |
| Symptoms | ||||
| Fever | 239 (71.1%) | 191 (72.3%) | 48 (66.7%) | 0.38 |
| Myalgia | 83 (24.7%) | 67 (25.4%) | 16 (22.2%) | 0.65 |
| Headache | 17 (5.1%) | 13 (4.9%) | 4 (5.6%) | 0.77 |
| Haemoptysis | 23 (6.8%) | 20 (7.6%) | 3 (4.2%) | 0.43 |
| Complication of influenza | ||||
| Pulmonary complication | 327 (97.3%) | 255 (96.6%) | 72 (100%) | 0.21 |
| Neurological complication | 7 (2.1%) | 5 (1.9%) | 2 (2.8%) | 0.65 |
| Myocarditis | 17 (5.1%) | 12 (4.5%) | 5 (6.9%) | 0.38 |
| Virology data | ||||
| Rapid influenza diagnostic test | 162 (48.2%) | 127 (48.1%) | 35 (48.6%) | 0.99 |
| Virus culture | 102 (30.4%) | 75 (28.4%) | 27 (37.5%) | 0.15 |
| RT-PCR | 266 (79.2%) | 207 (78.4%) | 59 (81.9%) | 0.62 |
| Influenza subtype A | 255 (75.9%) | 204 (77.3%) | 51 (70.8%) | 0.28 |
| Influenza subtype B | 27 (8%) | 18 (6.8%) | 9 (12.5%) | 0.14 |
| Laboratory data | ||||
| White blood cell counts (/ml) | 8900 (6008–13 500) | 8800 (5850–16 155) | 8920 (6100–13 210) | 0.52 |
| Haemoglobin (mg/dl) | 11.9 (9.6–13.7) | 11.2 (9.2–13.8) | 12 (9.7–13.5) | 0.60 |
| Platelet count (103/ml) | 145 (102–202.2) | 135 (81.3–196.0) | 149 (107–204.8) | 0.21 |
| C reactive protein (mg/dl) | 13.9 (6.1–22.6) | 16.3 (7.495–24.935) | 12.9 (6.0–20.8) | 0.07 |
| Blood urea nitrogen (mg/dl) | 22 (14.4–43.3) | 30 (19–54.5) | 20.8 (13.9–40) | 0.01 |
| Creatinine (mg/dl) | 1.1 (0.8–1.9) | 1.5 (1.0–2.6) | 1.0 (0.8–1.7) | 0.01 |
| Sodium (mg/dl) | 137 (133–140) | 138 (132–141) | 137 (133–140) | 0.55 |
| Potassium (mg/dl) | 3.9 (3.5–4.4) | 4 (3.5–4.7) | 3.9 (3.5–4.3) | 0.20 |
| Management | ||||
| First-dose oseltamivir (days) | 0.6 (0.1–1.9) | 0.5 (0.1–1.9) | 0.6 (0.1–1.9) | 0.77 |
| ICU wait (days) | 0.2 (0–1.0) | 0.2 (0–0.9) | 0.2 (0–1.0) | 0.70 |
| Prone ventilation | 65 (19.3%) | 48 (18.2%) | 17 (23.6%) | 0.31 |
| ECMO | 53 (15.8%) | 33 (12.5%) | 20 (27.8%) | <0.01 |
| Haemodialysis | 36 (10.7%) | 19 (7.2%) | 17 (23.6%) | <0.01 |
| Steroid usage | 144 (46.3%) | 103 (42.4%) | 41 (60.3%) | 0.01 |
| Vasopressor usage | 110 (32.7%) | 80 (30.3%) | 30 (41.7%) | 0.09 |
| Sedation usage | 222 (66.1%) | 175 (66.3%) | 47 (65.3%) | 0.89 |
Data were presented as frequencies (percentages) or median (IQR).
APACHE II, Acute Physiology and Chronic Health Evaluation II; ECMO, extracorporeal membrane oxygenation; ICU, intensive care unit; PSI, pneumonia severity index; RT-PCR, reverse transcriptase-polymerase chain reaction.