Table 1 Comparison between the training set and the validation set
| Â | 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 |