Utility of expiratory thin-section CT for fibrotic interstitial pneumonia

Background Collagen vascular disease-associated interstitial lung disease (CVD-ILD) must be differentiated from idiopathic pulmonary fibrosis (IPF) since prognosis and treatment strategies differ between these two conditions. However, differentiating between CVD-ILD and IPF is often difficult. Purpose To examine the utility of expiratory high-resolution computed tomography (HRCT) for differentiating between CVD-ILD and IPF. Material and Methods Seventy patients were examined with expiratory and inspiratory HRCT with CVD-ILD (n = 36) or IPF (n = 34). Associated diagnoses in patients with CVD-ILD were rheumatoid arthritis (n = 22), Sjögren syndrome (n = 3), scleroderma (n = 2), polymyositis/dermatomyositis (n = 1), and unspecified connective tissue disease (n = 8). Parenchymal abnormalities on inspiratory HRCT and visual extent of air trapping on expiratory HRCT were evaluated, statistical differences in HRCT findings between the two conditions were determined, and air trapping CT scores were correlated with the results of pulmonary function testing. Results Air trapping was found in 27 (75%) of 36 cases of CVD-ILD and four (12%) of 34 cases of IPF. Seventeen of the 27 cases for which air trapping was exhibited with CVD-ILD were diagnosed with rheumatoid arthritis. A significant difference in frequency of air trapping was seen between CVD-ILD and IPF (P