What radiographic features are common in COVID-19 patients?

The incidence of chest radiograph (CXR) abnormality appears to be lower in a cohort of swab-positive coronavirus disease (COVID-19) patients, including those identified from contact tracing, than previously reported, a Singapore study has found. Ground-glass opacity or consolidation was the predominant pattern, but mixed central and peripheral involvement is more common than peripheral involvement alone.

“CXR is widely used as a tool for prompt initial evaluation and subsequent management of COVID-19 pneumonia,” the researchers said. “Improved understanding of the patterns of radiographic findings will enhance diagnostic workflow and the appropriate use of CXR in public health measures to deal with the current pandemic.”

This retrospective review included swab-positive COVID-19 patients admitted to four different hospitals in Singapore between 22 January and 9 March 2020. Three experienced radiologists reviewed initial and follow-up CXR to identify the predominant pattern and distribution of lung parenchymal abnormalities.

A total of 347 CXR of 96 patients were reviewed. Of the patients, 41 (42.7 percent) had abnormal initial CXR. The mean time from onset of symptoms to CXR abnormality was 5.3 days (range, 1–21). Ground-glass opacity on initial CXR (51.2 percent) and consolidation on follow-up CXR (51.0 percent) were the most common pattern of lung abnormality. [Singapore Med J 2020;doi:10.11622/smedj.2020142]

“This is in line with the published literature, which reported ground-glass opacities, mixed ground-glass opacities, and consolidation as the predominant lung parenchymal abnormalities on computed tomography (CT),” the researchers said. [Radiology 2020;295:202-207; Radiology 2020;295:200463; Radiology 2020;296:E15-25; AJR Am J Roentgenol 2020;214:1072-1077; AJR Am J Roentgenol 2020;214:1287-1294]

“Our results showed an almost equal proportion of ground-glass opacity and consolidation in both the initial and follow-up radiographs, with a slight predominance for ground-glass opacity. It is known that CT has higher sensitivity for detecting mild ground-glass opacities compared to CXR,” they added.

Furthermore, multifocal bilateral abnormalities in mixed central and peripheral distribution were noted in 63.4 percent of abnormal initial and 59.2 percent of follow-up CXR. The lower zones were involved in 90.2 percent and 93.9 percent of the initial and follow-up CXR, respectively.

SARS-CoV-2, the causative agent of COVID-19, tends to invade the bronchioles and cause bronchiolitis and peribronchitis with subsequent distal spread, which brings about initial ground-glass opacity and subsequent lobular patchy opacity when the entire secondary pulmonary lobule is involved, according to a previous study. [J Infect 2020;81:e33-39]

“Variable findings [of] COVID-19 pneumonia, depending on the time course of the disease at which the imaging is taken, may pose a diagnostic challenge to radiologists,” the researchers noted.

Chest CT might be used when urgent detection and diagnosis of COVID-19 infection is needed while awaiting results from respiratory samples, according to the researchers. However, this depended on the pretest probability of COVID-19.

“For these reasons, we do not recommend CT as an initial diagnostic test,” they said. “This is in line with the recent recommendations by the American College of Radiology and the British Society of Thoracic Imaging, which state that CT should be utilized for specific clinical indications, and not be used to screen for COVID-19 or as a first-line test to diagnose COVID-19.” [https://www.acr.org/Advocacy-and-Economics/ACR-PositionStatements/Recommendations-for-Chest-Radiography-and-CT-for-Suspected-COVID19-Infection; https://www.bsti.org.uk/standards-clinical-guidelines/clinical-guidelines/covid-19-bstistatement-and-guidance/]

In addition, the Fleischner Society recently published a consensus statement recommending imaging for patients with mild symptoms who are at risk of disease progression, patients with moderate to severe features, and those with worsening respiratory status. [Radiology 2020;296:172-180]