Background Interstitial pneumonia (IP) may precede the clinical onset of connective tissue diseases (CTD). Idiopathic pulmonary fibrosis (IPF) is fibrosing pneumonia of an unknown cause, and has a poor prognosis. The differentiation between IP and IPF, raises a considerable diagnostic challenge as they share overlapping features. High resolution computed tomography (HRCT) has been put forth as a surrogate to recognize pathological IP, assessing distribution and predominance of key radiological findings such as ground glass opacities (GGOs) (Mink and Maycher, 2012 and Walash, et al., 2013).
Objectives To examine whether the radiographic features of idiopathic pulmonary fibrosis (IPF) and interstitial pneumonia (IP) of connective tissue diseases (CTD), as assessed by high resolution computed tomography (HRCT) which can be used to distinguish between these two entities.
Methods This study included 100 selected patients with CTD, with clinical diagnosis with IP, 27males and 73 females, (68 rheumatoid arthritis, 18 systemic lupus erythematosus, 7 scleroderma, and 7 ankylosing spondylitis), 40 patients with IPF and 20 controls. Those patients were recruited from Out-patients clinics of Rheumatology and Chest Departments of Assiut and Alazhar university hospitals. A standardized pulmonary evaluation was systematically conducted and included determination of patient's smoking history, occupation, environmental exposure and determination of pulmonary symptoms. Pulmonary function tests (PFTs) were done and included FEV1, FVC, RV, TLC, FEF 25-75%, FEF50% and FEF75%, and DLCO. ANA, anti-dsDNA, ENA (Sm, and La), U1-snRNP, C3, C4, RF, Acl, LA and plain radiography for chest and HRCT were done. HRCT scans were reviewed at 5 levels scored by 2 observers working independently. They evaluated the extent and distribution (reticulation, honeycombing and GGOs, were estimated to the nearest 5%). The relative proportions of interstitial lung disease (up to the total of 100%) made up of reticular pattern and GGOs were quantified.
Results The median extent of IP in patients with CTD was less than that in patients with IPF (P<0.001). The coarseness of fibrosis was significantly less course in patients with CTD than in patients with IPF (P<0.001).The proportion of GGOs was greater in patients with CTD than in those with IPF (P<0.001). IPF was characterized by a lower proportion of GGOs (P<0.001). Comparing groups of patients, a significant decrease of fibrosis, and a higher proportion of GGOs were found in CTD (P<0.001), while there was a significant increase of fibrosis and a lower proportion of GGOs in IPF (P<0.001). There was HRCT evidence of emphysema in 19.4% of IP patients and 12% of IPF patients.
Conclusions High resolution computed tomography has a beneficial role in diagnosing and differentiation between idiopathic pulmonary fibrosis and interstial pneumonia of connective tissue diseases.
Mink SN,and Maycher B (2012): Comparative manifestations and diagnostic accuracy of HRCT in usual interstitial pneumonia and nonspecific IP. Curr. Opin. Pulm. Med. 18(5):530-4.
Walsh et al. (2013): CTD related fibrotic lung disease:HRCT and pulmonary function indices as prognostic determinants. Thorax, p. thoraxjnl-2013-203843v2.
Disclosure of Interest None declared