Table 1.
Comparison between the training set and the validation set
| Total (n = 4663) | Training set (n = 3238) | Validation set (n = 1425) | P value | |
|---|---|---|---|---|
| Demographic | ||||
| Age | 55.0 [37.0;67.0] | 56.0 [41.0;68.0] | 53.0 [30.0;66.0] | < 0.001 |
| Sex, male | 1841 (39.5%) | 1182 (36.5%) | 659 (46.2%) | < 0.001 |
| Symptoms and signs | ||||
| Initial body temperature | 36.8 [36.5;37.3] | 36.9 [36.5;37.3] | 36.8 [36.5;37.2] | 0.001 |
| Cough | 1944 (41.7%) | 1523 (47.0%) | 421 (29.5%) | < 0.001 |
| Sputum | 1344 (28.8%) | 1049 (32.4%) | 295 (20.7%) | < 0.001 |
| Hemoptysis | 26 (0.6%) | 23 (0.7%) | 3 (0.2%) | 0.058 |
| Sore throat | 682 (14.6%) | 514 (15.9%) | 168 (11.8%) | < 0.001 |
| Rhinorrhea | 440 (9.4%) | 334 (10.3%) | 106 (7.4%) | 0.002 |
| Chest pain | 351 (7.5%) | 294 (9.1%) | 57 (4.0%) | < 0.001 |
| Myalgia | 733 (15.7%) | 583 (18.0%) | 150 (10.5%) | < 0.001 |
| Arthralgia | 18 (0.4%) | 16 (0.5%) | 2 (0.1%) | 0.124 |
| Lethargic | 179 (3.8%) | 143 (4.4%) | 36 (2.5%) | 0.003 |
| Dyspnea | 632 (13.6%) | 528 (16.3%) | 104 (7.3%) | < 0.001 |
| Headache | 773 (16.6%) | 612 (18.9%) | 161 (11.3%) | < 0.001 |
| Nausea, vomiting | 216 (4.6%) | 171 (5.3%) | 45 (3.2%) | 0.002 |
| Diarrhea | 400 (8.6%) | 333 (10.3%) | 67 (4.7%) | < 0.001 |
| Medical history | ||||
| Pregnancy | 17 (0.4%) | 12 (0.4%) | 5 (0.4%) | 1.000 |
| Diabetes | 704 (15.1%) | 510 (15.8%) | 194 (13.6%) | 0.067 |
| Heart failure | 66 (1.4%) | 40 (1.2%) | 26 (1.8%) | 0.151 |
| Hypertension | 1183 (25.4%) | 847 (26.2%) | 336 (23.6%) | 0.068 |
| Chronic cardiac disease | 188 (4.0%) | 138 (4.3%) | 50 (3.5%) | 0.261 |
| Asthma | 118 (2.5%) | 93 (2.9%) | 25 (1.8%) | 0.033 |
| COPD | 40 (0.9%) | 34 (1.1%) | 6 (0.4%) | 0.048 |
| Chronic kidney disease | 56 (1.2%) | 45 (1.4%) | 11 (0.8%) | 0.101 |
| Cancer | 154 (3.3%) | 111 (3.4%) | 43 (3.0%) | 0.526 |
| Chronic liver disease | 72 (1.5%) | 51 (1.6%) | 21 (1.5%) | 0.897 |
| Chronic neurologic disorder | 41 (0.9%) | 23 (0.7%) | 18 (1.3%) | 0.091 |
| Chronic hematologic disorder | 34 (0.7%) | 27 (0.8%) | 7 (0.5%) | 0.280 |
| HIV infection | 9 (0.2%) | 7 (0.2%) | 2 (0.1%) | 0.856 |
| Autoimmune disease | 32 (0.7%) | 25 (0.8%) | 7 (0.5%) | 0.380 |
| Dementia | 320 (6.9%) | 172 (5.3%) | 148 (10.4%) | < 0.001 |
| Smoking | < 0.001 | |||
| Never smoker | 4280 (91.8%) | 3034 (93.7%) | 1246 (87.4%) | |
| Ex-smoker | 131 (2.8%) | 94 (2.9%) | 37 (2.6%) | |
| Current smoker | 252 (5.4%) | 110 (3.4%) | 142 (10.0%) | |
| ADL | < 0.001 | |||
| Normal | 4011 (86.0%) | 2884 (89.1%) | 1127 (79.1%) | |
| Partially dependent | 358 (7.7%) | 194 (6.0%) | 164 (11.5%) | |
| Totally dependent | 294 (6.3%) | 160 (4.9%) | 134 (9.4%) | |
| Imaging and laboratory findings | ||||
| Chest X-ray infiltration | 1650 (35.4%) | 1229 (38.0%) | 421 (29.5%) | < 0.001 |
| Hemoglobin level, g/dL | 13.2 [12.1;14.4] | 13.2 [12.2;14.3] | 13.3 [12.1;14.5] | 0.066 |
| Platelet count, 103/μL | 224.0 [176.0;280.0] | 227.0 [178.0;283.0] | 218.0 [175.0;273.0] | 0.002 |
| WBC count, 103/μL | 5.7 [4.4;7.1] | 5.7 [4.5; 7.2] | 5.7 [4.4; 7.0] | 0.301 |
| Lymphocyte, % | 28.7 [20.9;36.2] | 28.7 [20.9;36.1] | 28.6 [21.3;36.5] | 0.638 |
| Hematocrit, % | 39.1 [36.2;42.3] | 39.0 [36.1;42.1] | 39.5 [36.2;42.8] | 0.018 |
| AST level, IU/L | 24.0 [19.0;33.0] | 25.0 [20.0;34.0] | 23.0 [19.0;32.0] | < 0.001 |
| ALT level, IU/L | 20.0 [14.0;31.0] | 20.0 [14.0;31.0] | 19.0 [13.0;30.0] | < 0.001 |
| Albumin level, g/dL | 4.2 [3.8;4.5] | 4.1 [3.8; 4.4] | 4.3 [3.9; 4.6] | < 0.001 |
| BUN level, mg/dL | 12.3 [10.0;15.8] | 12.5 [10.0;16.0] | 12.0 [9.7;15.0] | < 0.001 |
| Creatinine level, mg/dL | 0.7 [0.6;0.9] | 0.7 [0.6; 0.9] | 0.8 [0.6; 0.9] | 0.342 |
| Outcomes | ||||
| Requiring ICU | 444 (9.5%) | 320 (9.9%) | 124 (8.7%) | 0.226 |
| Admission to ICU | 213 (4.6%) | 113 (3.5%) | 70 (5.0%) | 0.016 |
| Mechanical ventilation | 49 (1.1%) | 35 (1.1%) | 14 (1.0%) | 0.697 |
| ECLS | 28 (0.6%) | 22 (0.7%) | 6 (0.4%) | 0.397 |
| Vasopressor treatment | 118 (2.5%) | 83 (2.6%) | 35 (2.5%) | 0.182 |
| Death | 217 (4.7%) | 141 (4.3%) | 76 (5.4%) | 0.113 |
Values are number (%) or median [interquartile range]
ADL activities of daily living, AST aspartate aminotransferase, ALT alanine aminotransferase, BUN blood urea nitrogen, COPD chronic obstructive pulmonary disease, ECLS extracorporeal life support, HIV human immunodeficiency virus, ICU intensive care unit, WBC white blood cell