Characteristics of study participants
| Patients with RA who have genotype data (n=2444) | Patients with RA who have chest CT* | P value in multivariable analysis | ||||
| Total (n=683) | RA-ILD (n=105) | RA-noILD (n=578) | P value in univariate analysis | |||
| Age at RA diagnosis | 43.0±12.8 | 45.9±13.0 | 50.9±12.3 | 45.0±13.0 | 1.3×10−5 | 1.4×10−4 |
| Age at ILD diagnosis | 65.7±10.7 | |||||
| Sex, female | 2141 (87.6) | 573 (83.9) | 82 (78.1) | 491 (84.9) | 0.079 | 0.807 |
| Smoking | ||||||
| Never | 2025/2434 (83.2) | 542/680 (79.4) | 79 (75.2) | 463/575 (80.5) | ||
| Ever | 221/2434 (9.1) | 71/680 (10.4) | 15 (14.3) | 56/575 (9.7) | 0.152 | 0.662 |
| Current | 188/2434 (7.7) | 67/680 (9.8) | 11 (10.5) | 56/575 (9.7) | 0.689 | 0.974 |
| RF positivity | 2058/2428 (84.8) | 619/683 (90.6) | 99 (94.3) | 520 (90.4) | 0.204 | 0.273 |
| Anti-CCP antibody positivity | 2097 (85.8) | 610 (89.3) | 101 (96.2) | 509 (88.1) | 0.013 | 0.064 |
| ILD pattern on chest CT* | ||||||
| UIP (or probable UIP) | 63 (60.0) | |||||
| Other than UIP† | 42 (40.0) | |||||
Values are presented as estimated means±SD or N (%).
*Of the patients who had chest CT scans, 11 patients with organising pneumonia were excluded.
†Patients with RA-ILD with other than UIP had the following patterns on chest CT: non-specific interstitial pneumonia or indeterminate for UIP.
CCP, citrullinated cyclic peptides; noILD, without ILD; RA, rheumatoid arthritis; RA-ILD, rheumatoid arthritis-interstitial lung disease; RF, rheumatoid factor; UIP, usual interstitial pneumonia.