|ECR 2019 / C-2418|
|HRCT features in patients with undifferentiated connective tissue disease|
Methods and materials
Study population: In this retrospective descriptive study, we reviewed CT scans obtained in 22 patients with a clinically and serologically diagnosis of UCTD who underwent a CT examination of the chest at Azienda Ospedaliero–Universitaria, Policlinico di Modena, Italy, during a mean 5 year follow up period (range 3 to 7 years).
The diagnosis of UCTD was made according to Mosca et al.  who proposed the following classification criteria: at least one clinical manifestation of CTDs without fulfilling the criteria of definite CTD, positive ANA (antinuclear antibodies) results and a disease duration as assessed from the onset of symptoms/signs of at least three years.
These 22 patients were identified from a clinical database provided by outpatient clinic of Rheumatology Unit of the same hospital. Our study group comprises 14 women and 8 men, who ranged in age from 32 to 83 years (mean, 64 years ± 12.9 [SD]).
All included patients underwent a CT examination of the chest because of their respiratory symptoms (dyspnea, cough and wheezing) and impairment of pulmonary function test results, particularly FVC and DLCO.
All of them are ex-smokers, except for one who is current smoker.
Data acquisition: High-resolution CT (HRCT) scans were obtained using a 64-slice scanner and were performed at baseline in all patients and followed up at a time of acute change in patient’s condition.
CT scans were obtained at maximal end-inspiratory phase with patients in the supine position; additional prone scan was performed optionally. No intravenous contrast material was administered. The images were acquired using helical scanning from the apices to the lung bases with a slice thickness < 2mm. Thin-section CT images were reconstructed with an edge-enhancing algorithm and were viewed at window setting optimized for assessment of lung parenchyma (window width, 1500 HU; window level, -700 HU) and soft tissue (window width, 400 HU; window level, 40 HU).
Data evaluation: All CT images were independently reviewed in a blind manner by two radiologists with 4 years of experience, without knowledge of patient's clinical information except for the UCTD diagnosis. A third expert chest radiologist (10 years of experience) assessed each CT scan and a final decision was reached with consensus of these three radiologists.
We evaluated the following CT features of lung parenchymal involvement, separately described as present or absent, including airspace consolidation, ground-glass opacity (GGO), reticulation (irregular linear opacities), airways abnormalities (bronchial wall thickening and parietal calcification), honeycombing, nodules, emphysema, traction bronchiectasis or bronchiolectasis, mosaic lung attenuation and air trapping.
The extent of three CT findings (reticulation, ground-glass and honeycombing) was graded with a five-point scale within the whole lung field. This scale describes the percentage of lung involvement: grade 0 (the finding was absent); grade 1 (1-25%), grade 2 (26-50%), grade 3 (51-75%), grade 4 (more than 76%).
A three-point scale was used to evaluate the extent of bronchiectasis: grade 0 (none), grade 1 (bronchiectasis localized within one bronchopulmonary segment), grade 2 (bronchiectasis extended into two or more segments).
Each patient was classified taking into account the predominant CT features and the radiologic pattern of ILD was interpreted according to the American Thoracic Society/European Respiratory Society statement on the Idiopathic Interstitial Pneumonias (2013). The CT pattern was recorded as UIP (usual interstitial pneumonia) pattern, NSIP (nonspecific interstitial pneumonia) pattern, OP (organizing pneumonia) pattern and indeterminate. 
The presence of additional findings was assessed, such as hiatal hernia, esophageal dilatation and pleural effusion.
The diameter of the pulmonary artery was recorded, measured at the widest diameter perpendicular to the long axis of the main pulmonary trunk, regarding as cut-off of normal pulmonary artery diameter as 29 mm. As recently reported, pulmonary artery size is accurate for detection pulmonary hypertension in patients both with and without ILD. 
At least, we evaluated the presence or absence of mediastinal lymph node enlargement, on the basis of criteria defined by Glazer et al. 
Statistical Analysis: Patients characteristics, CT findings of lung involvement and CT pattern were reported as frequency counts and percentages.
Interobserver agreement between the first two radiologists was determined by calculating the k value about pulmonary CT findings. The agreement was evaluated using the following scale: fair agreement (k value 0.21-0.40), moderate agreement (0.41-0.60), good agreement (0.61-0.80), excellent agreement (>0.81).
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