Demographic, clinical, serological and functional characteristics at IIM-ILD diagnosis in the IIM-ILD population, categorised as PF-ILD or non-PF-ILD patients
| Total population n=79 | PF-ILD n=14 | non-PF-ILD n=64 | P value | |
| Demographics | ||||
| Male—n (%) | 24 (30) | 5 (36) | 19 (29) | 0.75 |
| Female—n (%) | 55 (70) | 9 (64) | 46 (72) | |
| Age at diagnosis—years | 57 (18–83) | 57.5 (44–81) | 57 (18–83) | 0.82 |
| Age at ILD diagnosis—years | 58 (18–80) | 57 (44–80) | 58 (18–79) | 0.99 |
| Follow-up duration—years | 4 (0–22) | 2 (0.25–13) | 5 (0–22) | 0.047 |
| Deaths—n (%) | 3 (4) | 1 (7) | 2 (3) | 0.45 |
| IIM clinical phenotype | ||||
| Polymyositis—n (%) | 16 (20) | 3 (21) | 13 (20) | 0.95 |
| Dermatomyositis—n (%) | 15 (19) | 3 (21) | 12 (19) | |
| Anti-synthetase syndrome—n (%) | 48 (61) | 8 (57) | 40 (61) | |
| Clinical features | ||||
| Muscular weakness—n (%) | 35 (44) | 6 (43) | 29 (45) | 0.90 |
| Dyspnoea—n (%) | 46 (58) | 8 (47) | 38 (54) | 0.93 |
| Dysphagia—n (%) | 6 (8) | 2 (14) | 4 (6) | 0.28 |
| Fever—n (%) | 20 (25) | 3 (21) | 17 (26) | 0.71 |
| Arthritis—n (%) | 19 (24) | 5 (36) | 14 (22) | 0.31 |
| Mechanic hands—n (%) | 18 (23) | 4 (29) | 14 (22) | 0.73 |
| Heliotropic rash—n (%) | 7 (9) | 4 (29) | 3 (5) | 0.02 |
| Raynaud’s phenomenon—n (%) | 18 (23) | 2 (14) | 16 (25) | 0.63 |
| Gottron’s sign—n (%) | 6 (8) | 1 (7) | 5 (8) | 0.94 |
| Gottron’s papules—n (%) | 8 (10) | 2 (14) | 6 (9) | 0.63 |
| Xerophthalmia—n (%) | 7 (9) | 4 (29) | 3 (5) | 0.02 |
| Xerostomia—n (%) | 9 (11) | 5 (36) | 4 (6) | 0.007 |
| Muscle involvement | ||||
| MMT-8 at diagnosis | 150 (70–150) | 150 (70–150) | 150 (70–150) | 0.88 |
| CK at diagnosis—U/L | 179 (31–7000) | 128 (40–4500) | 400 (31–7000) | 0.30 |
| Myositis (biopsy and/or MRI)—n (%) | 34 (43) | 3 (21) | 31 (48) | 0.08 |
| Autoantibody profile | ||||
| Myositis-specific antibodies—n (%) | 59 (75) | 11 (79) | 48 (74) | 0.38 |
| Myositis-associated antibodies—n (%) | 44 (56) | 5 (36) | 39 (60) | 0.14 |
| Anti-synthetase—n (%) | 51 (65) | 8 (57) | 43 (66) | 0.55 |
| ENA—n (%) | 60 (76) | 11 (79) | 49 (75) | 0.99 |
| ANA—n (%) | 56 (71) | 8 (57) | 48 (74) | 0.33 |
| Anti-Jo1—n (%) | 36 (46) | 5 (36) | 31 (48) | 0.56 |
| Anti-PL12—n (%) | 7 (9) | 2 (14) | 5 (8) | 0.60 |
| Anti-PL7—n (%) | 7 (9) | 1 (7) | 6 (9) | 0.99 |
| Anti-Pm/Scl—n (%) | 13 (16) | 0 (0) | 13 (20) | 0.11 |
| Anti-SSA—n (%) | 37 (47) | 6 (43) | 31 (48) | 0.78 |
| Anti-SSB—n (%) | 4 (5) | 0 (0) | 4 (6) | 1.00 |
| Anti-U1RNP—n (%) | 3 (4) | 1 (7) | 2 (3) | 0.45 |
| Anti-Ku—n (%) | 3 (4) | 1 (7) | 2 (3) | 0.45 |
| Anti-TIF1γ—n (%) | 0 (0) | 0 (0) | 0 (0) | – |
| Anti-Ro52—n (%) | 28 (35) | 4 (29) | 24 (37) | 0.76 |
| Anti-MDA5—n (%) | 8 (10) | 4 (29) | 4 (6) | 0.03 |
| Anti-EJ—n (%) | 1 (1) | 0 (0) | 1 (2) | 0.99 |
| Anti-SRP—n (%) | 4 (5) | 1 (7) | 3 (5) | 0.55 |
| Anti-ASMA—n (%) | 0 (0) | 0 (0) | 0 (0) | – |
| Anti-MI2—n (%) | 3 (4) | 0 (0) | 3 (5) | 1.00 |
| Anti-SAE1—n (%) | 0 (0) | 0 (0) | 0 (0) | – |
| Pulmonary function tests | ||||
| FVC—L | 2.58 (1.21–4.22) | 3.27 (1.56–4.08) | 2.57 (1.21–4.22) | 0.29 |
| FVC—% pred. | 84 (47–146) | 89 (53–146) | 83 (47–121) | 0.36 |
| TLC—L | 4.43 (2.22–7.30) | 4.27 (3.06–5.39) | 4.54 (2.22–7.30) | 0.78 |
| TLC—% pred. | 80 (47–126) | 79 (62–126) | 80 (47–119) | 0.94 |
| DLCO—% pred. | 58 (28–102) | 59 (35–91) | 55 (21–102) | 0.68 |
| KCO—% pred. | 78 (42–143) | 83 (66–99) | 77 (42–143) | 0.51 |
Values are expressed as numbers and (%) or median and Q1–Q3 as appropriate.
ANA, anti-nuclear antibodies; CK, creatine kinase; DLCO, diffusion lung CO; DM, dermatomyositis; ENA, extractable nuclear antigen; FVC, forced vital capacity; IIM, idiopathic inflammatory myopathy; ILD, interstitial lung disease; KCO, carbon monoxide transfer coefficient; MDA5, anti-melanoma differentiation-associated gene; MMT, manual muscle test; PF, pulmonary function; RNP, ribonucleoprotein; SAE, small ubiquitin-like modifier-1 activating enzyme; SRP, signal recognition particle; TIF1γ, transcription intermediary factor 1-gamma; TLC, total lung capacity.