Chest radiography findings of COVID-19 pneumonia: a specific pattern for a confident differential diagnosis

Abstract

Background: Chest radiography (CR) patterns for the diagnosis of COVID-19 have been established. However, they were not ideated comparing CR features with those of other pulmonary diseases.

Purpose: To create the most accurate COVID-19 pneumonia pattern comparing CR findings of COVID-19 and non-COVID-19 pulmonary diseases and to test the model against the British Society of Thoracic Imaging (BSTI) criteria.

Material and methods: CR of COVID-19 and non-COVID-19 pulmonary diseases, admitted to the emergency department, were evaluated. Assessed features were interstitial opacities, ground glass opacities, and/or consolidations and the predominant lung alteration. We also assessed uni-/bilaterality, location (upper/middle/lower), and distribution (peripheral/perihilar), as well as pleural effusion and perihilar vessels blurring. A binary logistic regression was adopted to obtain the most accurate CR COVID-19 pattern, and sensitivity and specificity were computed. The newly defined pattern was compared to BSTI criteria.

Results: CR of 274 patients were evaluated (146 COVID-19, 128 non-COVID-19). The most accurate COVID-19 pneumonia pattern consisted of four features: bilateral alterations (Expß=2.8, P=0.002), peripheral distribution of the predominant (Expß=2.3, P=0.013), no pleural effusion (Expß=0.4, P=0.009), and perihilar vessels' contour not blurred (Expß=0.3, P=0.002). The pattern showed 49% sensitivity, 81% specificity, and 64% accuracy, while BSTI criteria showed 51%, 77%, and 63%, respectively.

Conclusion: Bilaterality, peripheral distribution of the predominant lung alteration, no pleural effusion, and perihilar vessels contour not blurred determine the most accurate COVID-19 pneumonia pattern. Lower field involvement, proposed by BSTI criteria, was not a distinctive finding. The BSTI criteria has lower specificity.

Keywords: COVID 19; SARS-CoV-2 virus; diagnostic X-ray; differential diagnosis; pneumonitis.

Fig. 1.

Chest radiography anatomical division. Location: Upper-middle-lower zones are identified by two anatomical landmarks: (a) the inferior wall of the aortic arch and (b) halfway between A and the dome of the lower hemi-diaphragm. Distribution: peripheral and perihilar zone are delimited by the halfway between the lateral edge of the lung and hilum (dotted line).

Fig. 2.

Flow chart of patients’ inclusion. ED, emergency department; RT-PCR, real-time reverse transcription polymerase chain reaction.

Fig. 3.

Application of COVID-19 pneumonia CR models. Sitting in AP CR, COVID-19 pneumonia fits our pattern: bilateral alterations, mostly sustained by GGO with a peripheral predominant distribution (consolidations are also present), absence of pleural effusion, and contour of perihilar vessels not blurred. The alterations mostly involve middle fields: this aspect does not fit the BSTI classic pattern. A nodule is also present in the upper zone of the right lung. Sitting in AP CR, COVID-19 pneumonia fits both our and BSTI classic patterns: bilateral alterations with predominant peripheral and lower involvement distribution (mostly by GGO in this example), absence of pleural effusion, pneumothorax or pulmonary edema, with contour of perihilar vessels not blurred. AP, anteroposterior; BSTI: British Society of Thoracic Imaging; CR, chest radiography; GGO, ground glass opacities.