Baseline characteristics and pulmonary physiology
| TOTAL | CTD-ILD | Non-CTD-ILD | CTD-ILD versus non-CTD-ILD p-value# | ||
| IPAF | IIP | ||||
| Subjects n | 96 | 27 | 27 | 42 | |
| Age years | 66.4±10.3 | 61.5±8.9 | 64.2±11.1 | 71.0±8.8 | 0.003 |
| Female n (%) | 43 (44.8) | 20 (74.1) | 15 (55.6) | 8 (19.0) | <0.001 |
| Smoking ever n (%) | 55 (57.3) | 10 (37.0) | 16 (59.3) | 29 (69.1) | 0.021 |
| Caucasian n (%) | 79 (82.3) | 19 (70.4) | 23 (85.2) | 37 (88.1) | 0.075 |
| Disease duration years | 7.4±7.7 | 11.3±10.6 | 4.3±3.0 | 6.9±6.5 | 0.002 |
| Respiratory symptoms years | 5.7±5.4 | 5.6±4.8 | 4.3±3.0 | 6.6±6.7 | 0.292 |
| Physiology | |||||
| SpO2 % | 96.6±2.5 | 97.9±2.4 | 96.7±2.3 | 95.8±2.4 | 0.003 |
| FVC % | 73.9±17.8 | 77.0±17.7 | 72.3±18.8 | 72.8±17.5 | 0.281 |
| DLCO % | 54.8±16.6 | 60.7±19.8 | 54.8±16.2 | 50.9±13.6 | 0.028 |
| 6 MWT distance metres | 446.5±126.1+ | 463.0±88.6¶ | 421.5±138.6ƒ | 453.1±137.3## | 0.479 |
| 6 MWT SpO2 nadir % | 90.0±7.1+ | 94.3±3.6¶ | 90.0±7.9ƒ | 87.6±7.2## | 0.001 |
| Composite indices | |||||
| CPI | 43.1±12.8 | 38.9±14.2 | 46.2±10.4 | 46.2±10.4 | 0.044 |
| ILD-GAP score | 1.9±2.2 | 0±1.6 | 1.2±1.5 | 2.5±1.5 | <0.001 |
Data represented as mean±sd unless otherwise stated. CTD-ILD: connective tissue disease associated ILD; IPAF: interstitial pneumonia with autoimmune features; IIP: idiopathic interstitial pneumonia; SpO2: peripheral oxygen saturation; FVC %: percentage predicted forced vital capacity; DLCO %: percentage predicted diffusing capacity for carbon monoxide; 6MWT: 6-min walk test; CPI: composite physiological index; ILD-GAP ILD: gender–age–physiology index. #: p-value for CTD-ILD versus non-CTD-ILD; ¶: n=22; +: n=82; §: n=60; ƒ: n=24; ##: n=36.