Positive Chest CT Features in Patients With COVID-19 Pneumonia and Negative Real-Time Polymerase Chain Reaction Test

Abstract

Objectives Clinically suspicious novel coronavirus (COVID-19) lung pneumonia can be observed typically on computed tomography (CT) chest scans even in patients with a negative real-time polymerase chain reaction (RT-PCR) test. The purpose of the study was to describe the CT imaging findings of five patients with negative RT-PCR results on initial and repeated testing but a high radiological suspicion of COVID-19 pneumonia. Methods Out of 19 clinically and/or radiologically diagnosed COVID-19 patients from our institution, five patients were selected for our study who had typical findings of COVID-19 on CT scan despite two negative RT-PCR results. Two district general hospital radiologists reviewed the chest CT images without prior knowledge of the RT-PCR test results. Scans were analyzed for the density of opacification and the distribution of disease. Results Out of 19 patients, five (26%) had initial negative RT-PCR test findings but positive CT chest features consistent with COVID-19. All patients had typical CT imaging findings of COVID-19. These included one patient with purely ground-glass opacities (GGO) and four patients with mixed GGO and consolidation. The typical distribution of parenchymal involvement was bilateral, posterior, and peripheral. Of the five patients with negative RT-PCR and positive CT findings, the range of CT severity score was 5 to 14. The median score, seen in three patients, was a score of 5, which corresponded to mild disease. One patient had a score of 8, corresponding to moderate disease, and one patient had severe disease with a score of 14. Conclusion Lung parenchymal changes related to COVID-19 can be seen on chest CT clearly despite repeated RT-PCR negative results.

Keywords: 2019-ncov; chest ct; covid-19; novel coronavirus; rt-pcr; sars-cov-2.

Figure 1. Patient selection flowchart

Figure 2. Patient 1

A 42-year-old female patient presented with a persistent cough and fever. Her D-dimer was 433 ng/mL and there was a clinical concern of a pulmonary embolus. A CT pulmonary angiogram (CTPA) scan was performed of the chest, which demonstrated changes consistent with COVID-19. A contrast-enhanced, axial CT image of the chest in lung windows showed bilateral patchy ground-glass opacification (white arrows). There was a large peripheral, posterior lesion in the left lower lobe in a distribution typical of COVID-19. There was also evidence of peripheral vascular engorgement (black arrows).

Figure 3. Patient 2

A 44-year-old female patient presented with persistent shortness of breath, pleuretic chest pain, and a raised D-dimer of more than 1400. A pulmonary embolus was suspected, and the patient was investigated with a CT pulmonary angiogram (CTPA). The CTPA showed no embolus; however, the patient did have features of COVID-19, which would account for her symptoms. Figure 3a demonstrates an axial, contrast-enhanced, CT image through the thorax, in lung windows. There was evidence of left basal consolidation (red box), right basal pleural thickening (white arrows), and basal vascular engorgement (black arrows).

Figure 4. Patient 2 axial CT

An axial computed tomography (CT) image in lung windows was taken at the level of the hila. The image shows a curvilinear subpleural reticular line (white arrows), vascular engorgement, and patchy peripheral and posterior ground glass opacification (red box).

Figure 5. Patient 3

A 53-year-old male patient was admitted to the emergency department with left-sided abdominal pain, decreased appetite, and vomiting. The patient was investigated with a whole-body computed tomography (CT), which demonstrated lung parenchymal changes consistent with COVID-19. (Figure 5a) An axial contrast-enhanced CT of the chest, in lung windows, demonstrates patchy bilateral ground glass and consolidative changes. There is evidence of bi-basal pleural thickening (white arrows), air bronchograms (black arrows), and mosaic attenuation (red box).

Figure 6. Patient 3 axial CT slice

An axial computed tomography (CT) slice through the chest in the same patient, in mediastinal windows, demonstrates mediastinal lymphadenopathy (white arrows).

Figure 7. Patient 4

A 51-year-old male patient was admitted to the emergency department with a two-day history of vomiting. His abdomen was distended, with palpable bowel loops. He was investigated with whole-body computed tomography (CT). His abdominal CT (not shown) demonstrated small bowel obstruction, and imaging of the chest showed evidence of parenchymal changes consistent with COVID-19. Figure 4 shows an axial contrast-enhanced CT image of the chest, in lung windows. The image shows left basal consolidation (red box) with air bronchograms (white arrows). There are multiple, right, lower lobe ground glass-opacities (black arrows).

Figure 8. Patient 5

A 51-year-old female received staging computed tomography (CT) of the chest as part of her work-up for newly diagnosed breast cancer. She was asymptomatic with regard to respiratory symptoms. Her CT scan of the chest showed incidental changes consistent with COVID-19. Her subsequent real-time polymerase chain reaction (RT-PCR) swab tests were negative. Follow-up imaging with a chest X-ray showed the resolution of the consolidative changes. (Figure 8a) Axial contrast-enhanced CT slice of the thorax. There are bilateral patchy ground-glass and consolidative changes. There is a patch of linear consolidation seen in the periphery of the right lower lobe, a typical morphology for COVID-19 (red box). There are multiple thickened and irregular septa in both lung bases (white arrows).

Figure 9. Patient 5 axial CT image

An axial computed tomography (CT) image from the same study, at the level of the lung bases, demonstrates multiple thickened and irregular septae and a curvilinear subpleural line (black arrows). These features are commonly seen in COVID-19 patients.