Table 1.

Baseline clinical characteristics of the connective tissue disease-associated interstitial lung disease (CTD-ILD) group are compared to those of the idiopathic pulmonary fibrosis (IPF) group, and baseline characteristics of the systemic sclerosis-associated ILD (SSc-ILD) group are compared to those of the non-SSc_ILD group. If a baseline value was unavailable for a subject, the first available observation for the variable was used. P values are derived from t-tests, Wilcoxon signed-rank tests, Mann-Whitney U test, or exact tests where appropriate. Data are mean (SD) unless otherwise specified. Values represented as percentages indicate the proportion of subjects who are positive for the variable.

Variable	CTD, n = 76		IPF n = 148		p, CTD vs IPF	SSc n = 26		Non-SSc n = 50		p, SSc vs Non-SSc
Variable	N		N			N		N
Baseline age, yrs	75	56.1 (13.7)	147	68.6 (12.1)	< 0.0001	25	49.8 (14.2)	50	59.2 (12.5)	0.004
BMI, kg/m²	61	29.1 (6.6)	117	29.4 (6.4)	0.758	19	26.2 (4.8)	42	30.5 (7)	0.017
ILD disease duration, yrs	63	6.2 (7.2)	123	1.7 (4)	< 0.0001	24	4.7 (5.6)	39	6.8 (7.7)	0.273
White, %	72	58	130	69	0.119	26	50	46	63	0.281
Sex, % women	76	80	148	42	< 0.0001	26	85	50	78	0.492
Ever smoker, %	65	52	126	68	0.041	25	56	40	50	0.638
GERD, %	76	32	131	34	0.767	26	39	50	28	0.352
Raynaud’s, %	76	40	125	2	< 0.0001	26	73	50	22	< 0.0001
Anemia, %	54	22	80	18	0.498	22	23	32	22	0.941
ANA-positive, %	48	81	40	25	< 0.0001	21	100	27	67	0.003
High muscle enzymes, %	51	18	72	14	0.570	18	17	33	18	0.892
Thyroid disease, %	76	15	148	11	0.425	26	12	50	16	0.600
UIP on HRCT, %	76	37	148	68	< 0.0001	26	27	50	42	0.265
FVC, % predicted	72	67.4 (21.9)	143	67.3 (20.2)	0.956	24	77.6 (20.2)	48	62.3 (21.1)	0.005
FEV1, % predicted	71	72 (22.2)	135	75.9 (23.3)	0.247	24	79.4 (19.5)	47	68.3 (22.7)	0.045
TLC, % predicted	45	71.8 (19.6)	118	66.9 (18.1)	0.133	15	80.9 (19.6)	30	67.3 (18.2)	0.026
DLCO, unadjusted % predicted	68	52 (18.4)	139	44.9 (18.7)	0.015	24	58.4 (19)	44	48.6 (17.3)	0.029
NYHA class	47	2 (0.8)	116	2.4 (0.8)	0.007	16	1.5 (0.7)	31	2.2 (0.7)	0.003
Exercise O₂ sat, %	36	93.3 (6)	55	89.7 (6.2)	0.002	11	96.3 (3.6)	25	91.9 (6.4)	0.016
O₂ sat ever < 90%, %	71	13	140	26	0.029	23	4	48	17	0.144

BMI: body mass index; GERD: gastroesophageal reflux disease; ANA-positive: antinuclear antibody ≥ 1:80; UIP: usual interstitial pneumonia; HRCT: high-resolution computed tomography; FVC: forced vital capacity; FEV1: forced expiratory volume in 1 second; TLC: total lung capacity; DLCO: diffusion capacity for carbon monoxide; NYHA: New York Heart Association; O₂ sat: oxygen saturation.