Clinical characteristics of study population. Values are n (%) unless otherwise specified.
| Characteristics | Total, n = 420 | SSc-PM, n = 24 | SSc, n = 396 | p, SSc-PM vs SSc |
|---|---|---|---|---|
| Age, yrs, mean (SD) | 50 (13.1) | 52 (12.1) | 50 (13.2) | 0.28 |
| Female | 273/420 (65) | 13/24 (54) | 260/396 (66) | 0.25 |
| Type SSc, lcSSc/dcSSc | 306 (73)/114 (27) | 19 (79)/5 (21) | 287 (73)/109 (27) | 0.47 |
| Disease duration since SSc, yrs, median (IQR) | 7.8 (3.9–14.1) | 6.3 (4.2–12.9) | 7.8 (3.9–14.1) | 0.85 |
| Disease duration since PM, yrs, median (IQR) | — | 5.7 (3.8–12.9) | — | — |
| Mortality | 73/420 (17) | 8/24 (33) | 65/396 (16) | 0.048 |
| SSc features | ||||
| RP | 400/420 (95) | 21/24 (88) | 379/396 (96) | 0.098 |
| Digital ulcers | 169/420 (40) | 5/24 (21) | 161/395 (41) | 0.046 |
| mRSS, median (IQR) | 7/386 (4–12) | 6/15 (5–11) | 7/371 (4–12) | 0.96 |
| Serology | ||||
| ANA | 318/420 (76) | 24/24 (100) | 294/396 (74) | 0.004 |
| Anticentromere | 78/414 (19) | 2/18 (11) | 76/396 (19) | 0.55 |
| Antitopoisomerase I | 86/416 (21) | 0/20 (0) | 86/396 (22) | 0.019 |
| Internal organ involvement | ||||
| ILD | 156/429 (37) | 14/24 (58) | 142/396 (36) | 0.027 |
| HRCT fibrosis | 185/364 (51) | 15/18 (83) | 170/346 (49) | 0.005 |
| X-thorax fibrosis | 61/414 (15) | 6/20 (30) | 55/394 (14) | 0.096 |
| TLC ≤ 70% of predicted | 71/273 (26) | 3/20 (15) | 68/253 (27) | 0.24 |
| TLCO ≤ 70% of predicted | 276/363 (76) | 16/16 (100) | 260/347 (75) | 0.016 |
| FEV1 ≤ 70% of predicted | 98/385 (25) | 6/22 (27) | 92/363 (25) | 0.84 |
| Diastolic dysfunction, cardiac | US153/371 (41) | 7/19 (37) | 146/352 (42) | 0.69 |
| PH suspicion by cardiac US | 92/372 (25) | 3/20 (15) | 89/352 (25) | 0.43 |
| PH by cardiac catheterization | 57/187 (31) | 0/5 (0) | 57/182 (31) | 0.33 |
| Renal crisis | 18/420 (4) | 1/24 (4) | 17/396 (4) | 1.0 |
SSc: systemic sclerosis; PM: polymyositis; lcSSc: limited cutaneous SSc; dcSSc: diffuse cutaneous SSc; IQR: interquartile range; RP: Raynaud phenomenon; mRSS: modified Rodnan skin score; ANA: antinuclear antibody; ILD: interstitial lung disease; HRCT: high-resolution computed tomography; TLC: total lung capacity of pulmonary function test; TLCO: transfer factor of the lung for carbon monoxide; FEV1: forced expiratory volume in 1 s; US: ultrasound; PH: pulmonary hypertension.