TABLE 1.
Baseline patient characteristics.
| Variables | Exposure to silica (N = 95) | No exposure to silica (N = 1,344) | P |
| Demographics | |||
| Age ≥ 50 years, N (%) | 25 (27.5) | 546 (41.5) | 0.016 |
| Male sex, N (%) | 43 (45.3) | 149 (11.1) | <0.001 |
| Caucasian, N (%) | 88 (92.6) | 1,204 (89.7) | 0.626 |
| Disease duration ≥ 5 years, N (%) | 47 (51.6) | 773 (58.9) | 0.207 |
| Smoking, N (%) | 67 (70.5) | 786 (58.7) | 0.065 |
| Clinical characteristics | |||
| Diffuse disease, N (%) | 48 (51.6) | 470 (35.3) | 0.003 |
| Treatment with CYC or MMF, N (%) | 14 (14.9) | 110 (8.3) | 0.082 |
| ILD, N (%) | 36 (38.3) | 393 (30.0) | 0.157 |
| FVC < 70, N (%) (n = 1,244) | 18 (21.7) | 130 (11.2) | 0.016 |
| Pulmonary arterial hypertension, N (%) (n = 909) | 8 (15.4) | 140 (16.3) | 0.208 |
| Rodnan score, median (IQR) | 10.00 [4.00, 17.50] | 6.00 [2.00, 14.00] | 0.011 |
| Digital ulcer/pitting scars, N (%) | 45 (47.9) | 556 (41.8) | 0.516 |
| Necrosis/gangrene/amputation, N (%) | 32 (34.0) | 473 (35.6) | 0.957 |
| Nailfold capillaroscopy, N (%) | 67 (71.3) | 1,017 (76.5) | 0.513 |
| GI_14, Median (IQR) (n = 1,343) | 4.00 [2.00, 7.00] | 3.00 [1.00, 6.00] | 0.014 |
| Joint impairment, N (%) | 23 (24.5) | 377 (28.3) | 0.721 |
| History of renal crisis, N (%) | 7 (7.4) | 48 (3.6) | 0.174 |
| Cancer, N (%) | 8 (8.5) | 108 (8.1) | 0.991 |
| Antibody profile | |||
| ACA antibody, N (%) (n = 1,244) | 24 (28.3) | 458 (39.5) | 0.075 |
| ATA antibody, N (%) (n = 1,244) | 18 (21.8) | 172 (14.8) | 0.189 |
| U1RNP, N (%) (n = 1,276) | 6 (7.0) | 63 (5.3) | 0.758 |
| Ro52, N (%) (n = 1,244) | 22 (25.8) | 309 (26.7) | 0.664 |
| Ku, N (%) (n = 1,244) | 0 (0.0) | 9 (0.7) | 0.477 |
| Nor90, N (%) (n = 1,244) | 1 (1.1) | 26 (2.2) | 0.54 |
| Nucleolar antibodies, N (%) (n = 1,243) | 18 (21.4) | 232 (20.0) | 0.795 |
| Medsger severity scores | |||
| Medsger—general, mean (SD) | 1.06 (1.37) | 0.89 (1.18) | 0.172 |
| Medsger—peripheral vascular, Mean (SD) (n = 1,156) |
1.88 (1.21) | 1.63 (1.24) | 0.097 |
| Medsger—skin, mean (SD) | 1.36 (0.77) | 1.21 (0.70) | 0.05 |
| Medsger—joint/tendon, Mean (SD) (n = 1,095) |
0.96 (1.32) | 0.68 (1.18) | 0.055 |
| Medsger—muscle, mean (SD) | 0.33 (0.90) | 0.23 (0.72) | 0.185 |
| Medsger—GI tract, mean (SD) | 2.07 (0.85) | 1.91 (0.78) | 0.049 |
| Medsger—lung, mean (SD) | 1.57 (1.21) | 1.30 (1.11) | 0.02 |
| Medsger—heart, mean (SD) | 0.56 (1.17) | 0.46 (0.95) | 0.354 |
| Medsger—kidney, mean (SD) (n = 1,266) | 0.16 (0.65) | 0.11 (0.61) | 0.473 |
IQR, interquartile range; SD, standard deviation; CYC, cyclophosphamide; MMF, mycophenolate mofetil; ACA, anticentromere antibody; ATA, anti-topoisomerase I antibody; U1RNP, anti-U1 Ribonucleoproteins antibody; ILD, interstitial lung disease; FVC, forced vital capacity; Unless a different denominator (n) is indicated, the missing number for remaining variables was < 5%.
Chi-square or fisher exact test for categorical variable. ANOVA or Kruskal-Wallis test for continuous variables.
N provided where > 5% of data was missing.
Bold indicates statistically significant values.