title: Utility of expiratory thin-section CT for fibrotic interstitial pneumonia.
abstract: 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.
  
  
  OBJECTIVE
  To examine the utility of expiratory high-resolution computed tomography (HRCT) for differentiating between CVD-ILD and IPF.
  
  
  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 < 0.0001). Frequency of centrilobular nodules was significantly higher in CVD-ILD than in IPF (P = 0.021). In contrast, frequencies of interlobular interstitial thickening and traction bronchiectasis were significantly higher in IPF than in CVD-ILD (P = 0.005, P = 0.007, respectively). Correlations were seen between visual extent of air trapping and pulmonary function test results such as air trapping index (P = 0.004, r = 0.34), closing volume/vital capacity (P = 0.0002, r = -0.47), and closing capacity/total lung capacity (P < 0.0001, r = -0.51).
  
  
  CONCLUSIONS
  The presence of air trapping on expiratory HRCT suggests CVD-ILD rather than IPF.
authors.affiliation: Department of Radiology, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai City, Japan.
authors.forename: Sayoko
authors.initials: S
authors.lastname: Tokura
authors.affiliation: Department of Radiology, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai City, Japan Department of Radiology, Osaka City University Graduate School of Medicine, Osaka City, Japan o-kuma@msic.med.osaka-cu.ac.jp.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Okuma
authors.affiliation: Department of Radiology, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai City, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Akira
authors.affiliation: Department of Internal Medicine, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai City, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Arai
authors.affiliation: Department of Internal Medicine, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai City, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Department of Pathology, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai City, Japan.
authors.forename: Masanori
authors.initials: M
authors.lastname: Kitaichi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D003240:Connective Tissue Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D054988:Idiopathic Interstitial Pneumonias / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: CT; Thorax; air trapping; lung