Background Pulmonary function tests play a key role in assessment of systemic sclerosis (SSc) pulmonary manifestations. Reduction of diffusing lung capacity for carbon monoxide (DLCO) is evidence both pulmonary arterial hypertension(PAH) and interstitial lung disease (ILD). Usually ILD progression is accompanied by appearance of restrictive failures of the pulmonary function when the reduction of breathing capacity happens in parallel with DLCO reduction. In some cases of definite ILD “isolated” reduction of DLCO can be detected as only abnormality of lung function, and its clinical value is unclear.
Objectives To estimate the clinical value of isolated reduction of DLCO in patients with SSc-ILD in absence of PAH within 5-year prospective study.
Methods 44 patients (41 women and 3 men; 32 patients (73%) with limited SSc and 12 patients (27%) with diffuse SSc), affected with reduction of DLCO below 80% of predicted values, with forced vital capacity (FVC) ≥ 80% of predicted values, in the absence of PAH on echocardiography (ECG) evidence (SPAP ≤ 35 mm Hg) were selected from 142 patients with definite diagnosis SSc, which were admitted to the Institute of Rheumatology in the 2006-2007s. Average age of the patients was 49 ± 13 years. Duration of the disease from the first non-Raynaud’s syndrome – 7,7 ± 6,8 years. ANA was found out for 41 (93%) patients, anti-centromiric antibodies (ACA) were found out in 5 (11%) patients, a-Scl-70 were found out in 24 (55 %) patients. SPAP was 40 and 45 mm Hg by ECG in two patients affected with severe pulmonary fibrosis. Patients underwent functional pulmonary tests (FVC % of predicted, DLCO % of predicted), chest high resolution computer tomography (HRCT), ECG, activity index (EScSG) was recorded at study entry and after 4,7 ± 1 years of follow up.
Results The CT-signs of ILD were revealed in 39 (89%) patients at study entry and they were additionally detected in 3 patients in at the end of the study. Value of FVC did not change significantly in group (98,3 ± 10 vs 100,3 ± 17,2) and DLCO significantly reduced (60,7 ± 13,3 (min 26 – max 70%) vs 57,2 ± 11,8 (min 32 – max 78%), p=0,01. SPAP remained within the normal range in most patients (27,6 ± 5,2 vs 27,8 ± 6). CT-signs of ILD were revealed in 3 of 5 patients with ACA at the first examination and their SPAP did not increase during the observation period.
A clinically significant FVC decrease (at ≥ 10%) at the time of the second observation was detected in 5 patients (in 3 of them radiological signs of ILD already existed at study entry), and in 2 cases radiological signs of IPL appeared during follow up observation. A-Scl-70 were revealed in all patients affected with FVC reduction and activity index remained above 3 both at study entry and after 5 years. A clinically significant DLCO reduction (at ≥ 10%) was found out in 10 (23%) patients. CT-signs of ILD were revealed in all of this 10 patients during the first examination and in addition, worsening of radiological signs of the pulmonary fibrosis was occurred in 6 patients in the dynamics.
Conclusions Isolated reduction of DLCO in patients with SSc may be the only sign of ILD for a long period of time. During follow up the clinically significant reduction of diffusing lung capacity was associated with the progression of radiological signs of the pulmonary fibrosis in the absence of pulmonary arterial hypertension.
Disclosure of Interest None Declared