Table 1. Baseline Characteristics of Data Sets.
| Variable | No. (%) | ||
|---|---|---|---|
| Institute 1 (n = 998) | Institute 2 (n = 246) | Institute 3 (n = 205) | |
| Sex | |||
| Male | 539 (54.0) | 133 (54.1) | 105 (51.2) |
| Female | 459 (46.0) | 113 (45.9) | 100 (48.8) |
| Age, mean (SD), y | 54.2 (9.82) | 55.3 (8.74) | 51.8 (9.13) |
| Normal radiographs | 423 (42.4) | 131 (53.2) | 113 (54.9) |
| Nodule chest radiographs | 575 (57.6) | 115 (46.8) | 92 (44.8) |
| Total No. of nodules | 598 | 119 | 92 |
| Nodule size on CT | 23.8 (8.8) | 24.4 (7.4) | 25.1 (8.7) |
| mean (SD), mm | |||
| 1.0 cm ≤ × < 2.0 cm | 198 (33.1) | 49 (41.2) | 28 (30.4) |
| 2.0 cm ≤ × < 3.0 cm | 400 (66.9) | 70 (58.8) | 64 (69.6) |
| Location | |||
| Right | |||
| Upper lobe | 160 (26.7) | 30 (25.2) | 25 (27.1) |
| Middle lobe | 36 (6.0) | 11 (9.2) | 10 (10.9) |
| Lower lobe | 131 (21.9) | 24 (20.2) | 22 (24.0) |
| Left | |||
| Upper lobe | 142 (23.7) | 29 (24.4) | 25 (27.1) |
| Lower lobe | 129 (21.7) | 25 (21.0) | 10 (10.9) |
| Internal characteristics of CT findings | |||
| Subsolid nodule | 32 (5.4) | 5 (4.2) | 3 (3.3) |
| Solid nodule | 566 (94.6) | 114 (95.8) | 89 (96.7) |
| Pathology | |||
| Benign | 65 (10.9) | 18 (15.1) | 10 (10.9) |
| Malignant (primary) | 483 (80.7) | 95 (79.8) | 74 (80.4) |
| Malignant (metastatic) | 50 (8.4) | 6 (5.1) | 8 (8.7) |
Abbreviation: CT, computed tomography.