Incidental diagnosis of Covid-19 pneumonia on chest computed tomography

Abstract

Purpose: The purpose of this study was to determine the prevalence and imaging characteristics of incidentally diagnosed COVID-19 pneumonia on computed tomography (CT).

Materials and methods: This retrospective study was conducted between March 20th and March 31st, 2020 at Cochin hospital, Paris France. Thoracic CT examinations of all patients referred for another reason than a suspicion of SARS-CoV-2 infection were reviewed. CT images were analyzed by a chest radiologist to confirm the presence of findings consistent with COVID-19 pneumonia and quantify disease extent. Clinical and biological data (C-reactive protein serum level [CRP] and white blood cell count) of patients with CT findings suggestive for COVID-19 pneumonia were retrieved from the electronic medical chart.

Results: During the study period, among 205 diagnostic CT examinations, six examinations (6/205, 3%) in 6 different patients (4 men, 2 women; median age, 57 years) revealed images highly suggestive of COVID-19 pneumonia. The final diagnosis was confirmed by RT-PCR. Three inpatients were suspected of extra thoracic infection whereas three outpatients were either fully asymptomatic or presented with fatigue only. All had increased CRP serum level and lymphopenia. Disease extent on CT was mild to moderate in 5/6 patients (83%) and severe in 1/6 patient (17%).

Conclusion: Cumulative incidence of fortuitous diagnosis if COVID-19 pneumonia did not exceed 3% during the highest pandemic phase and was predominantly associated with limited lung involvement.

Keywords: COVID-19 pneumonia; Computed tomography; Incidental findings; Multidetector.

Fig. 1

A 86-year-old asymptomatic woman with suspicion of lung cancer (Patient # 3). A, CT image of the thorax in the axial plane shows spiculated solid nodule (arrow) in right upper lobe. B, At a different level, sub pleural ground glass opacities are seen bilaterally, with superimposed intralobular thickening resulting in a crazy-paving pattern (arrowhead) in the right lower lobe.

Fig. 2

A 30-year-old asymptomatic woman treated with antibiotics for post-partum endometritis who has unexplained persistent fever (Patient #5). A, B, Unenhanced CT images in the axial plane show focal ground glass opacities and consolidations. C, At a different level, CT image shows subpleural, curvilinear lines in left lower lobe (arrow).