TABLE 2

Pulmonary function tests of the studied population at inclusion, divided into four groups: systemic sclerosis (SSc) patients without any pulmonary involvement, i.e. neither interstitial lung disease (ILD) nor pulmonary hypertension (Group A), SSc patients with ILD but without pulmonary hypertension (Group B), SSc patients with both ILD and pulmonary hypertension (Group C), and SSc patients without ILD but with pulmonary hypertension (Group D)

	Group A	Group B	Group C	Group D	p-value
Subjects	313	201	35	23
FEV₁
L	2.49±0.66^#,¶,+	2.28±0.63⁺	2.00±0.64	1.87±0.63	<0.0001
% pred	102±20^#,¶,+	91±20	83±20	86±22	<0.0001
FVC
L	3.21±0.79^#,¶,+	2.88±0.85	2.64±0.87	2.56±0.89	<0.0001
% pred	111±20^#,¶,+	95±22	90±22	97±23	<0.0001
FEV₁/FVC % (actual)	78±8^#,+	80±8	77±12	73±7	<0.0001
SVC
L	3.32±0.80^#,¶,+	2.93±0.87	2.65±0.77	2.52±0.68	<0.0001
% pred	114±20^#,¶,+	96±23	91±21	99±22	<0.0001
TLC
L	5.20±0.95^#,¶	4.76±1.31	4.63±1.13	4.87±1.01	<0.0001
% pred	105±15^#,¶	89±19	86±17	97±18	<0.0001
FRC
L	3.02±0.63^#	2.79±0.86	2.87±0.83	2.83±0.73	0.023
% pred	109±21^#,¶	96±24	94±22	101±22	<0.0001
RV
L	1.97±0.52^#	1.80±0.64⁺	1.84±0.52	2.19±0.80	0.001
% pred	106±25^#,¶	91±28	90±24	107±38	<0.0001
T_LCO
mL·mmHg^–1·min^–1	18.4±5.6^#,¶,+	14.6±6.0^¶,+	9.6±3.3	9.7±4.3	<0.0001
% pred	81±22^#,¶,+	63±22^¶,+	44±19	49±21	<0.0001
T_LNO
mL·mmHg^–1·min^–1	91.0±27.7^#,¶,+	71.9±26.5^¶,+	51.2±18.0	48.9±17.0	<0.0001
% pred	67±22^#,¶,+	56±23^¶,+	43±17	40±14	<0.0001
T_LNO/T_LCO	5.06±1.20	5.16±1.28	5.46±1.42	5.78±2.61	0.036
Hb g·100 mL^–1	13.4±1.4⁺	13.1±1.4	13.0±2.0	12.5±1.7	0.014
V_C
mL	45±18^#,¶,+	37±18^¶	25±11	27±15	<0.0001
% pred	72±25^#,¶,+	58±26^¶	43±23	47±24	<0.0001
D_MCO
mL·mmHg^–1·min^–1	104±105^#	74±38	85±97	105±244	0.008
% pred	106±101^#	73±38	73±60	138±345	0.0008
D_MCO/V_C	2.77±5.19⁺	2.38±1.87⁺	4.90±8.29	7.66±24.5	0.002

Data are presented as n or mean±sd. FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; SVC: slow vital capacity; TLC: total lung capacity; FRC: functional residual capacity; RV: residual volume; T_LCO: transfer factor of the lung for carbon monoxide; T_LNO: transfer factor of the lung for nitric oxide; Hb: haemoglobin concentration; V_C: alveolar capillary blood volume; D_MCO: membrane conductance (diffusing capacity) for carbon monoxide. ^#: p<0.05 versus Group B; ^¶: p<0.05 versus Group C; ⁺: p<0.05 versus Group D.