Table 1 Patient characteristics

Age, years

65.1 ± 9.8

62.5 ± 9.5

68.5 ± 9.6

0.113

Sex, Female

16 (61.5)

9 (60.0)

7 (63.6)

1.000

Former or current smoker

11 (42.3)

6 (40.0)

5 (45.5)

1.000

UIP-like fibrotic pattern on high-resolution CT

14 (53.9)

9 (60.0)

5 (45.5)

0.692

Primary CTD

Systemic sclerosis (SSc)

11 (42.3)

8 (53.3)

3 (27.3)

0.246

Polymyositis, Dermatomyositis (PM/DM)

6 (23.1)

3 (20.0)

3 (27.3)

1.000

Rheumatoid arthritis (RA)

4 (15.4)

2 (13.3)

2 (18.2)

1.000

Microscopic polyangiitis (MPA)

3 (11.5)

0 (0)

3 (27.3)

0.064

Eosinophilic granulomatosis with polyangiitis (EGPA)

1 (3.8)

1 (6.7)

0 (0)

1.000

Sjögren’s syndrome (SS)

1 (3.8)

1 (6.7)

0 (0)

1.000

Duration of CTD, years

9.8 ± 8.3

9. 0 ± 6.4

6.1 ± 5.2

0.232

Duration of CTD-ILD, years

7.7 ± 5.6

9. 0 ± 6.4

5.9 ± 3.9

0.299

Criteria for disease progression over the past 24 months

Relative decline in FVC of ≥ 10% of the predicted value

7 (26.9)

3 (20.0)

4 (36.4)

0.407

Relative decline in FVC of ≥ 5% to ≤ 10% of the predicted value, along with worsening respiratory symptoms or increased extent of fibrosis on high-resolution CT.

6 (23.1)

4 (26.7)

2 (18.2)

1.000

Worsening respiratory symptoms and increased extent of fibrosis on high-resolution CT

13 (50.0)

8 (53.3)

5 (45.5)

1.000

Additional immunosuppressive agents administered following the diagnosis of CTD-associated PF-ILD

Rituximab

6 (24.0)

0 (0)

6 (54.6)

0.002^**

Glucocorticoids (≥ 20 mg/day of prednisolone equivalent)

4 (15.4)

0 (0)

4 (36.4)

0.022*

Abatacept

2 (7.7)

0 (0)

2 (18.2)

0.169

Cyclophosphamide

1 (3.8)

0 (0)

1 (9.1)

0.423

Mycophenolate mofetil

1 (4.0)

0 (0)

1 (9.1)

0.423

Tacrolimus

1 (4.0)

0 (0)

1 (9.1)

0.423