Table 1.
Patient characteristics
| Characteristic | Overall (N=418) | Development cohort (N=282) | Validation cohort (N=136) | P value |
| Age | 56.0 (50.0–65.8) | 55.5 (50.0–66.0) | 56.0 (50.0–65.0) | 0.496 |
| Gender | 0.811 | |||
| Female | 264 (63%) | 177 (63%) | 87 (64%) | |
| Male | 154 (37%) | 105 (37%) | 49 (36%) | |
| Smoking | 0.175 | |||
| Absent | 310 (76%) | 204 (74%) | 106 (80%) | |
| Present | 97 (24%) | 71 (26%) | 26 (20%) | |
| Unknown | 11 | 7 | 4 | |
| Cough | 0.630 | |||
| Absent | 61 (15%) | 43 (16%) | 18 (14%) | |
| Present | 337 (85%) | 227 (84%) | 110 (86%) | |
| Unknown | 20 | 12 | 8 | |
| Breathless | 0.740 | |||
| Absent | 37 (10%) | 26 (11%) | 11 (9.4%) | |
| Present | 327 (90%) | 221 (89%) | 106 (91%) | |
| Unknown | 54 | 35 | 19 | |
| Fever | 0.430 | |||
| Absent | 286 (69%) | 196 (70%) | 90 (66%) | |
| Present | 130 (31%) | 84 (30%) | 46 (34%) | |
| Unknown | 2 | 2 | 0 | |
| Heliotrope sign | 0.056 | |||
| Absent | 354 (85%) | 232 (83%) | 122 (90%) | |
| Present | 63 (15%) | 49 (17%) | 14 (10%) | |
| Unknown | 1 | 1 | 0 | |
| Gottron sign | 0.454 | |||
| Absent | 219 (53%) | 144 (51%) | 75 (55%) | |
| Present | 198 (47%) | 137 (49%) | 61 (45%) | |
| Unknown | 1 | 1 | 0 | |
| Myasthenia | 0.588 | |||
| Absent | 334 (80%) | 223 (79%) | 111 (82%) | |
| Present | 83 (20%) | 58 (21%) | 25 (18%) | |
| Unknown | 1 | 1 | 0 | |
| Arthralgia | 0.169 | |||
| Absent | 326 (78%) | 214 (76%) | 112 (82%) | |
| Present | 90 (22%) | 66 (24%) | 24 (18%) | |
| Unknown | 2 | 2 | 0 | |
| HRCT | 0.258 | |||
| NSIP | 156 (37%) | 100 (35%) | 56 (41%) | |
| OP or UIP | 262 (63%) | 182 (65%) | 80 (59%) | |
| MDA5 | 0.228 | |||
| Negative | 272 (65%) | 178 (63%) | 94 (69%) | |
| Positive | 146 (35%) | 104 (37%) | 42 (31%) | |
| RO52 | 0.072 | |||
| Negative | 161 (39%) | 117 (41%) | 44 (32%) | |
| Positive | 257 (61%) | 165 (59%) | 92 (68%) | |
| WBC | 7.4 (5.4–10.0) | 7.2 (5.4–10.0) | 7.7 (5.4–10.0) | 0.724 |
| PLT | 226.5 (173.0–285.8) | 227.0 (173.3–295.3) | 226.0 (172.0–276.8) | 0.467 |
| Lymphocyte | 1.1 (0.8–1.7) | 1.2 (0.7–1.7) | 1.1 (0.8–1.7) | 0.840 |
| CD3+CD4+ T | 0.4 (0.2–0.6) | 0.4 (0.2–0.6) | 0.3 (0.2–0.5) | 0.150 |
| Unknown | 3 | 3 | 0 | |
| LDH | 298.5 (236.5–422.3) | 292.0 (232.8–408.3) | 320.5 (246.5–439.3) | 0.058 |
| Unknown | 2 | 2 | 0 | |
| CRP | 6.7 (3.8–21.4) | 6.7 (3.8–20.7) | 6.7 (3.9–21.6) | 0.805 |
| IgG | 12.0 (9.6–14.7) | 12.3 (9.7–14.8) | 11.3 (9.4–14.6) | 0.123 |
| Unknown | 5 | 3 | 2 | |
| ESR | 27.5 (16.0–44.0) | 28.0 (16.0–45.8) | 26.0 (13.0–41.5) | 0.158 |
| CK | 49.0 (30.0–102.3) | 47.5 (30.0–94.5) | 55.0 (32.8–123.8) | 0.161 |
| Unknown | 2 | 2 | 0 | |
| FVC% | 61.8 (50.7–71.5) | 62.1 (52.0–71.5) | 61.2 (47.3–71.4) | 0.506 |
| Unknown | 185 | 125 | 60 | |
| FEV1% | 67.2 (55.9–75.8) | 67.4 (56.4–75.0) | 67.2 (53.6–77.8) | 0.608 |
| Unknown | 189 | 128 | 61 | |
| DLCO% | 53.0 (43.0–65.0) | 51.7 (43.2–64.6) | 53.6 (41.1–67.5) | 0.786 |
| Unknown | 185 | 125 | 60 | |
| PO2 | 73.0 (64.0–85.0) | 73.0 (64.0–86.0) | 71.5 (63.8–82.8) | 0.483 |
| Unknown | 1 | 1 | 0 | |
| PCO2 | 35.4 (32.8–39.8) | 35.5 (33.0–39.6) | 35.2 (32.2–39.8) | 0.988 |
| Unknown | 45 | 31 | 14 | |
| PaO2/FiO2 | 310.0 (220.0–376.0) | 319.0 (220.0–380.0) | 305.0 (218.8–376.0) | 0.248 |
| Unknown | 1 | 1 | 0 |
Data are given as median (IQR) or n (%). A Gottron’s sign and inverse Gottron’s sign were pooled in data collection.
CK, creatine kinase; CRP, C reactive protein; DLCO%, diffusing capacity of the lung for carbon monoxide predicted; ESR, erythrocyte sedimentation rate; FiO2, fraction of inspiration O2; FVC%, forced vital capacity predicted; HRCT, high-resolution CT; IgG, immunoglobulin G; LDH, lactate CT; MDA5, melanoma differentiation-associated gene 5; NSIP, non-specific interstitial pneumonia; OP, organising pneumonia; PLT, platelets; UIP, usual interstitial pneumonitis; WBC, white cell counts.