Table 1.
Characteristics of patients with RA in the discovery sample (ESPOIR)*
| Patient group | |||||
|---|---|---|---|---|---|
| Characteristic | Overall RA (n = 163) | RA‐ILD (n = 31) | RA without ILD (n = 132) | OR or ES or HR (95% CI) | P † |
| Characteristic at RA onset | |||||
| Male sex | 35 (21.5) | 12 (38.7) | 23 (17.4) | 2.99 (1.28, 7.01) | 0.01 |
| White race/ethnicity | 150 (92.6) | 27 (87.1) | 123 (93.9) | 2.28 (0.64, 8.11) | 0.25 |
| Age, median (IQR) years | 49.4 (41.2–55.1) | 56.2 (50.6–61.4) | 47.6 (38.5–53.7) | −0.84 (−1.24, −0.43)‡ | <0.0001 |
| BMI median (IQR) kg/m2 | 24.0 (21.5–27.4) | 24.9 (23.0–28.9) | 23.7 (21.4–27.0) | −0.23 (−0.62, −0.17)‡ | 0.11 |
| Ever smoker | 77 (47.2) | 17 (54.8) | 60 (45.5) | 1.46 (0.66, 3.20) | 0.42 |
| Smoking exposure, median (IQR) pack‐years | 0 (0–15) | 8 (0–20) | 0 (0–13) | −0.37 (−0.77, 0.03)‡ | 0.11 |
| DAS28‐ESR, median (IQR) | 5.2 (4.5–6.1) | 5.5 (4.7–6.2) | 5.1 (4.4–6.0) | −0.04 (−0.43, 0.36)‡ | 0.48 |
| CRP, median (IQR) mg/dl | 10.0 (4.0–22.8) | 9.0 (4.5–20.5) | 10.0 (4.0–22.5) | 00.7 (−0.33, 0.43)‡ | 0.69 |
| ACPA positive | 96 (58.9) | 20 (64.5) | 76 (57.6) | 1.34 (0.59, 3.02) | 0.55 |
| ACPA titer, median (IQR) units/ml | 394 (0.0–500) | 429 (0–500) | 325 (0–500) | −0.10 (−0.50, 0.29)‡ | 0.68 |
| RF positive | 128 (78.5) | 24 (77.4) | 104 (78.8) | 0.92 (0.36, 2.36) | 0.81 |
| RF titer, median (IQR) units/ml | 30 (5–95) | 50 (5–161) | 16 (6–43) | −0.16 (−0.55, 0.24)‡ | 0.33 |
| ANA positive | 61 (37.4) | 10 (32.3) | 51 (38.6) | 0.76 (0.33, 1.74) | 0.54 |
| Sicca syndrome | 111 (68.1) | 19 (61.3) | 92 (69.7) | 0.69 (0.31, 1.55) | 0.40 |
| Erosive status | 29 (17.8) | 7 (11.1) | 22 (17.7) | 1.46 (0.56–3.80) | 0.44 |
| Total SHS, median (IQR) | 2.0 (0.0–4.0) | 2.0 (0.0–4.0) | 2.0 (0.0–4.0) | −0.19 (−0.61, 0.23)‡ | 0.59 |
| HAQ score, median (IQR) | 1.0 (0.5–1.5) | 1.1 (0.5–1.4) | 1.0 (0.5–1.5) | −0.07 (−0.47, 0.32)‡ | 0.83 |
| HLA–DRB1*SE allele presence | 0.93 | ||||
| 0 | 68 (42.8) | 14 (45.2) | 54 (42.2) | 1 (referent) | |
| 1 | 65 (40.9) | 13 (42.0) | 52 (40.6) | 0.96 (0.41, 2.25) | |
| 2 | 26 (16.4) | 4 (12.9) | 22 (17.2) | 0.70 (0.21, 2.37) | |
| MUC5B rs35705950 GT/TT genotype, % | 11.3 | 19 | 9.5 | 2.91 (1.22, 6.95) | 0.02 |
| Longitudinal variables at time of chest | |||||
| HRCT scan | |||||
| RA duration, median (IQR) years | 13.9 (13–14.1) | 13.9 (13.3–14) | 13.9 (13–14.1) | 0.82 (0.55, 1.22)§ | 0.30 |
| Smoking status trajectory | |||||
| Never–stop/low | 131 (80.4) | 22 (71.0) | 109 (82.6) | 1 (referent) | 0.21 |
| Maintained/moderate–high | 32 (19.6) | 9 (29.0) | 23 (17.4) | 1.94 (0.79, 4.75) | |
| DAS28‐ESR, median (IQR) | 2.9 (2.4–3.7) | 3.4 (2.7–4.1) | 2.9 (2.3–3.5) | −0.47 (−0.87, −0.07)‡ | 0.03 |
| CRP, median (IQR) mg/dl | 5.8 (3.9–9.2) | 6.6 (3.9–9.2) | 5.8 (4.1–8.7) | −0.38 (−0.78, 0.01)‡ | 0.42 |
| CRP trajectory | |||||
| None–low | 147 (90.2) | 25 (80.6) | 122 (92.4) | 1 (referent) | 0.09 |
| Moderate–high | 16 (9.8) | 6 (19.4) | 10 (7.6) | 2.93 (0.91, 8.79) | |
| HAQ score, median (IQR) | 0.4 (0.2–0.8) | 0.6 (0.3–1.1) | 0.4 (0.2–0.6) | −0.01 (−0.4, 0.39)‡ | 0.007 |
| MTX exposure | 138 (84.7) | 27 (87.1) | 111 (84.1) | 1.28 (0.40, 4.03) | 0.79 |
| MTX exposure trajectory | |||||
| None–low | 51 (31.3) | 12 (38.7) | 39 (29.6) | 1 (referent) | 0.64 |
| Moderate | 76 (46.6) | 13 (41.9) | 63 (47.7) | 0.67 (0.28, 1.62) | |
| High | 36 (22.1) | 6 (19.4) | 30 (22.7) | 0.65 (0.22, 1.93) | |
| bDMARD exposure | 66 (40.5) | 14 (45.2) | 52 (39.4) | 1.27 (0.58, 2.79) | 0.68 |
| TNF inhibitor exposure | 54 (33.1) | 14 (45.2) | 40 (30.3) | 1.89 (0.85, 4.21) | 0.14 |
| Glucocorticoid exposure trajectory | 0.84 | ||||
| None–low | 60 (36.8) | 13 (41.9) | 47 (35.6) | 1 (referent) | |
| Moderate | 30 (18.4) | 5 (16.2) | 25 (18.9) | 0.72 (0.23, 2.26) | |
| High | 73 (44.8) | 13 (41.9) | 60 (45.5) | 0.78 (0.33, 1.85) | |
| ILD pattern on chest HRCT | – | ||||
| UIP and probable UIP | – | 4 (12.9) | – | – | |
| NSIP | – | 4 (12.9) | – | – | |
| Indeterminate | – | 23 (74.2) | – | – | |
| Extent of ILD on chest HRCT | – | ||||
| <5% | – | 7 (22.6) | – | – | |
| 5–10% | – | 15 (48.4) | – | – | |
| >10% | – | 9 (29.0) | – | – | |
| Pulmonary function test results, median (IQR) | – | ||||
| FVC, % predicted | – | 110 (91.8–117) | |||
| FEV1, % predicted | – | 96 (90.3–113) | – | – | |
| TLC, % predicted | – | 104 (92.3–108.3) | – | – | |
| DLco, % predicted | 77 (62–80) | – | – | ||
Except where indicated otherwise, results (qualitative variables) are the number (%); quantitative variables are shown as median and interquartile range (IQR). The odds ratio (OR) with 95% confidence interval (95% CI) represents the likelihood of a qualitative variable being higher in the rheumatoid arthritis–associated interstitial lung disease (RA‐ILD) group than in the RA without ILD group. Erosive status indicates presence of articular erosions due to RA. The effect size (ES) with 95% CI represents the effect size of a quantitative variable being higher in the RA‐ILD group than in the RA without ILD group. BMI = body mass index; DAS28‐ESR = Disease Activity Score in 28 joints using the erythrocyte sedimentation rate; CRP = C‐reactive protein; ACPA = anti–citrullinated peptide antibody; RF = rheumatoid factor; ANA = antinuclear antibody; SHS = modified Sharp/van der Heijde score of radiographic progression; HAQ = Health Assessment Questionnaire; HLA–DRB1*SE = HLA–DRB1 shared epitope; HRCT = high‐resolution computed tomography; MTX = methotrexate; bDMARD = biologic disease‐modifying antirheumatic drug; TNF = tumor necrosis factor; UIP = usual interstitial pneumonia; NSIP = nonspecific interstitial pneumonia; FVC = forced vital capacity, FEV1 = forced expiratory volume in 1 second; TLC = total lung capacity; DLco = diffusing capacity for carbon monoxide.
Results from the bivariate analysis.
ES with 95% CI.
Hazard ratio (HR) with 95% CI.