Table 1.
Characteristics of the study population
| Variables | No bacterial coinfection (N = 3943) |
Bacterial coinfection (N = 133) |
p value |
|---|---|---|---|
| Age, median (Q1; Q3), years | 63 (54; 71) | 65 (55; 72) | 0.369 |
| Male sex, n (%) | 2777 (70) | 86 (65) | 0.547 |
| BMI, median (Q1; Q3), kg/m2 | 28.9 (26.1; 32.3) | 29.5 (26.1; 32.3) | 0.105 |
| Comorbidities, n (%)a | 1758 (45) | 73 (55) | 0.019 |
| Diabetes mellitus | 961 (24) | 39 (29) | 0.192 |
| Chronic liver disease | 119 (3) | 9 (7) | 0.036 |
| Chronic heart disease | 469 (12) | 25 (19) | 0.016 |
| Chronic lung disease | 564 (14) | 30 (23) | 0.008 |
| Chronic renal failure | 242 (6) | 5 (4) | 0.258 |
| Immunosuppression | 131 (4) | 4 (3) | > 0.999 |
| Days from first symptoms to hospital admission, median (Q1; Q3) | 7 (4; 8) | 7 (5; 9) | 0.091 |
| Days from initial symptoms to ICU admission, median (Q1; Q3) | 9 (7; 12) | 7 (6; 10) | < 0.001 |
| Days from hospital admission to ICU admission, median (Q1; Q3) | 2 (0; 4) | 0 (0; 1) | < 0.001 |
| Treatment before admission, n (%) | |||
| Corticosteroids | 278 (7) | 11 (8) | 0.591 |
| Antibiotics | 0 (0) | 10 (8) | < 0.001 |
| Characteristics at hospital admission | |||
| Glasgow Coma Scale, median (Q1; Q3) | 15 (15; 15) | 15 (15; 15) | < 0.001 |
| Temperature, median (Q1; Q3), °C | 37.3 (36.5; 38.1) | 37.1 (36.2; 37.8) | 0.006 |
| Respiratory rate, median (Q1; Q3), bpm | 25 (20; 30) | 26 (22; 32) | 0.035 |
| Arterial blood gases at hospital admission | |||
| PaO2/FiO2 ratio, median (Q1; Q3) | 200 (105; 277) | 165 (100; 237) | 0.017 |
| PaO2/FiO2 ratio in ventilated patients at hospital admission, median (Q1; Q3)b | 133 (83; 229) | 122 (95; 179) | 0.340 |
| PaO2/FiO2 ratio categories in ventilated patients at hospital admission, n (%)b | 0.001 | ||
| Severe (< 100) | 439 (35) | 24 (32) | 0.582 |
| Moderate (≥ 100–< 200) | 418 (33) | 39 (52) | 0.001 |
| Mild (≥ 200–< 300) | 252 (20) | 12 (16) | 0.381 |
| No ARDS (≥ 300) | 141 (11) | 0 (0) | 0.002 |
| pH, median (Q1; Q3) | 7.44 (7.4; 7.47) | 7.42 (7.35; 7.46) | < 0.001 |
| PaCO2, median (Q1; Q3), mmHg | 34.3 (30.7; 40) | 37 (32; 43) | 0.001 |
| PaCO2 in vetilated patients at hospital admission, median (Q1; Q3), mmHgb | 35 (31; 42) | 36 (32; 45.7) | 0.158 |
| Laboratory findings at hospital admission | |||
| Haemoglobin, median (Q1; Q3), g/dL | 14 (12.9; 15.1) | 13.6 (12.5; 14.9) | 0.016 |
| Leucocyte count, median (Q1; Q3), 109/L | 7 (5.2; 9.9) | 8.3 (6.1; 11.5) | < 0.001 |
| Neutrophil count, median (Q1; Q3), 109/L | 5.6 (3.9; 8.4) | 6.9 (5; 10.1) | < 0.001 |
| Platelet count, median (Q1; Q3), 109/L | 190 (148; 247) | 207 (174; 280) | 0.001 |
| D-dimer, median (Q1; Q3), ng/mL | 670 (376; 1282) | 890 (456; 1810) | 0.004 |
| Procalcitonin, median (Q1; Q3), ng/mL | 0.19 (0.1–0.44) | 0.26 (0.12 to 0.94) | 0.010 |
| C-reactive protein, median (Q1; Q3), mg/L | 131 (70; 213) | 163 (109; 242) | < 0.001 |
| Serum creatinine, median (Q1; Q3), mg/dL | 0.95 (0.78; 1.2) | 0.96 (0.75; 1.25) | 0.977 |
| LDH, median (Q1; Q3), U/L | 420 (321; 568) | 492 (372; 647) | 0.003 |
| Ferritin, median (Q1; Q3), ng/mL | 921 (464; 1650) | 1080 (543; 1676) | 0.149 |
| Respiratory support at hospital admissionc | < 0.001 | ||
| Conventional oxygen therapy | 2365 (60) | 49 (37) | < 0.001 |
| High-flow nasal cannula | 700 (18) | 18 (14) | 0.196 |
| Non-invasive mechanical ventilation | 378 (10) | 8 (6) | 0.159 |
| Invasive mechanical ventilation | 470 (12) | 58 (44) | < 0.001 |
| Patients undergoing invasive mechanical ventilation in the first 48 h from hospital admission | 1352 (34) | 99 (74) | < 0.001 |
ICU indicates intensive care unit, Q1 first quartile, Q3 third quartile; BMI, body mass index, PaO2 partial pressure of arterial oxygen, FiO2 fraction of inspired oxygen, LDH lactate dehydrogenase, ECMO extracorporeal membrane oxygenation. Percentages calculated on non-missing data. p values marked in bold indicate numbers that are statistically significant on the 95% confidence limit
aPossibly > 1 comorbidity
bPatients who received high-flow nasal cannula, non-invasive ventilation or invasive mechanical ventilation at hospital admission
cPatients who received high-flow nasal cannula but needed non-invasive ventilation were included in the non-invasive mechanical ventilation group. Patients who received high-flow nasal cannula and/or non-invasive ventilation but needed intubation were included in the invasive mechanical ventilation group