Baseline characteristics of the study population(full analysis set)
| Characteristics | High dose | Low dose | Placebo | p-value# |
| Subjects | 108 | 55 | 104 | |
| Male | 85 (78.7) | 47 (85.5) | 81 (77.9) | 0.53 |
| Female | 23 (21.3) | 8 (14.5) | 23 (22.1) | |
| Age yrs | 65.4±6.2 | 63.9±7.5 | 64.7±7.3 | 0.44 |
| Smoking history | ||||
| Smokers | 5 (4.6) | 10 (18.2) | 13 (12.5) | 0.07¶ |
| Ex-smokers | 81 (75.0) | 33 (60.0) | 70 (67.3) | |
| Never smokers | 22 (20.4) | 12 (21.8) | 21 (20.2) | |
| Time since first diagnosis yrs | ||||
| <1 | 38 (35.2) | 20 (36.4) | 41 (39.4) | 0.86 |
| 1–3 | 29 (26.9) | 13 (23.6) | 25 (24.0) | |
| ≥3 | 41 (38.0) | 22 (40.0) | 38 (36.5) | |
| Prior treatment (steroids) received | ||||
| No | 99 (91.7) | 49 (89.1) | 98 (94.2) | 0.49 |
| Yes | 9 (8.3) | 6 (10.9) | 6 (5.8) | |
| Current steroid use | 8 (7.4) | 6 (10.9) | 5 (4.8) | |
| Surgical lung biopsy | 26 (24.1) | 16 (29.1) | 28 (26.9) | 0.78 |
| VC mL | 2400.8±638.4 | 2437.8±684.8 | 2472.3±698.9 | 0.74 |
| VC % pred | 77.3±16.8 | 76.2±18.7 | 79.1±17.4 | 0.57 |
| TLC % pred | 73.2±16.5 | 72.4±15.6 | 75.2±15.7 | 0.50 |
| DL,CO % pred | 52.1±16.8 | 53.6±19.1 | 55.2±18.2 | 0.44 |
| Pa,O2 at rest mmHg | 79.8±10.2 | 81.6±8.4 | 81.0±9.5 | 0.48 |
| PA–a,O2 mmHg | 18.4±11.3 | 16.9±9.6 | 17.4±9.7 | 0.64 |
| Lowest Sp,O2 % | 89.0±2.3 | 88.8±2.4 | 89.0±2.0 | 0.86 |
| Presence of desaturation below 88% on walk test | 34 (31.5) | 19 (34.5) | 24 (23.1) |
Data are presented as n, n (%) or mean±sd, unless stated otherwise. VC: vital capacity; % pred: % predicted; TLC: total lung capacity; DL,CO: diffusion capacity of the lung for carbon monoxide; Pa,O2: arterial oxygen tension; PA–a,O2: alveolar–arterial oxygen tension difference; Sp,O2: oxygen saturation measured by pulse oximetry. #: using Fisher's exact test, Kruskal–Wallis test and ANCOVA in accordance with nominal and binary, ordinal and continuous data, respectively. VC, TLC, DL,CO, Pa,O2 and PA–a,O2 were measured for 106 subjects in the high-dose pirfenidone group, and TLC and DL,CO for 103 subjects in the placebo group. ¶: p<0.15.