Table 1 General characteristics of the samples
Variable, n (%) | Total (N = 992) | Derivation cohort (n = 707) | Validation cohort (n = 285) | p |
|---|---|---|---|---|
Influenza subtype | ||||
A | 846 (85.3%) | 561 (79.3%) | 285 (100.0%) | < 0.001 |
B | 145 (14.5%) | 145 (20.5%) | 0 (0.0%) | |
Both | 1 (0.1%) | 1 (0.1%) | 0 (0.0%) | |
Age (median, IQR) | 79 (66–85) | 79 (65–85) | 79 (67–85) | > 0.20 |
Sex (male) | 522 (52.6%) | 372 (52.6%) | 150 (52.6%) | > 0.20 |
Days since symptoms (median, IQR) | 3 (2–5) | 3 (2–6) | 3 (1–4) | < 0.001 |
Symptoms lasting > 72 h | 427 (43.6%) | 327 (47.1%) | 100 (35.1%) | 0.001 |
Influenza vaccine | 480 (48.4%) | 325 (46.0%) | 155 (54.4%) | 0.017 |
Hypertension | 672 (67.7%) | 484 (68.5%) | 188 (66.0%) | > 0.20 |
Pregnancy | 9 (0.9%) | 7 (1.0%) | 2 (0.7%) | > 0.20 |
Current smokers | 126 (12.8%) | 91 (12.9%) | 35 (12.7%) | > 0.20 |
Obesity | 196 (45.6%) | 108 (46.0%) | 88 (45.1%) | > 0.20 |
Asthma | 90 (9.1%) | 73 (10.3%) | 17 (6.0%) | 0.03 |
COPD | 242 (24.4%) | 172 (24.3%) | 70 (24.6%) | > 0.20 |
Diabetes mellitus | 276 (27.8%) | 206 (29.1%) | 70 (24.6%) | 0.15 |
Cardiovascular disease | 348 (35.1%) | 240 (33.9%) | 108 (37.9%) | > 0.20 |
Chronic kindney disease | 176 (17.7%) | 127 (18.0%) | 49 (17.2%) | > 0.20 |
Liver disease | 53 (5.3%) | 36 (5.1%) | 17 (6.0%) | > 0.20 |
Neurologic disorder | 170 (17.1%) | 188 (16.7%) | 52 (18.2%) | > 0.20 |
Immunosupression (*) | 177 (17.8%) | 132 (18.7%) | 45 (15.8%) | > 0.20 |
CCI (median. IQR) | 2 (1–4) | 2 (1–5) | 2 (1–3) | < 0.001 |
CCI > 2 points | 620 (62.8%) | 458 (65.2%) | 162 (56.8%) | 0.01 |
Respiratory rate (median, IQR) | 20 (16–25) | 18 (16–24) | 22 (16–28) | < 0.001 |
pO2 on room air (median, IQR) | 56 (50–64) | 57 (50–65) | 54 (50–61) | 0.004 |
SpO2 on room air (median, IQR) | 91 (88–95) | 92 (88–95) | 91 (87–95) | 0.099 |
SpO2 on room air < 94% | 627 (66.6%) | 440 (66.4%) | 187 (67.0%) | > 0.20 |
Radiological abnormalities | 396 (41.7%) | 274 (40.5%) | 122 (44.9%) | > 0.20 |
Secondary pneumonia | 161 (16.4%) | 135 (19.1%) | 26 (9.5%) | < 0.001 |
Lymphocyte count (cells/µl) (median, IQR) | 700 (400–1000) | 700 (400–1000) | 700 (400–1000) | > 0.20 |
LDH (U/l) (median, IQR) | 275 (224–335) | 287 (246–348) | 228 (188–292) | < 0.001 |
Respiratory failure | 81 (8.2%) | 48 (6.8%) | 33 (11.6%) | 0.01 |
Admission to ICU | 49 (4.9%) | 30 (4.2%) | 19 (6.7%) | 0.11 |
Mechanical ventilation | ||||
NIPPV | 36 (3.6%) | 18 (2.5%) | 18 (6.3%) | 0.004 |
IMV | 22 (2.2%) | 19 (2.7%) | 3 (1.1%) | 0.11 |
Mortality | ||||
In hospital (overall) | 47 (4.8%) | 33 (4.7%) | 14 (4.9%) | > 0.20 |
30-day | 25 (2.6%) | 18 (2.5%) | 7 (2.6%) | > 0.20 |
Evolution after discharge | ||||
Recovery without sequelae | 794 (80.3%) | 592 (84.1%) | 202 (70.9%) | < 0.001 |
Recovery with sequelae | 148 (15.0%) | 79 (11.2%) | 69 (24.2%) | |
Length of hospital stay (days. median. IQR) | 7 (5–13) | 7 (5–12) | 8 (5–16) | 0.013 |