ACEP COVID-19 Field Guide

The CDC does not currently recommend chest CT or chest x-ray (CXR) as a diagnostic method for COVID-19 infection. As such, a CXR may not need to be a part of the workup for a patient with mild disease; however, it may be useful if diagnostic ambiguity is present.

Article summary: ACR recommendations for the use of chest radiography and computed tomography for suspected COVID-19 infection

American College of Radiology. ACR recommendations for the use of chest radiography and computed tomography (CT) for suspected COVID-19 infection. Published 2020 Mar 11. Updated 2020 Mar 22.

Based on the risks of misdiagnosis and viral transmission, the American College of Radiology (ACR) recommends that CT should not be used to screen for or as a first-line test to diagnose COVID-19. CT should be reserved for hospitalized, symptomatic patients with specific clinical indications. 

The ACR believes that the following factors should be considered regarding the use of imaging for suspected or known COVID-19 infection:

• The CDC does not currently recommend CXR or CT to diagnose COVID-19. Viral testing remains the only specific method of diagnosis. Confirmation with the viral test is required, even if radiologic findings are suggestive of COVID-19 on CXR or CT.
• For the initial diagnostic testing for suspected COVID-19 infection, the CDC recommends collecting and testing specimens from the upper respiratory tract (nasopharyngeal and oropharyngeal swabs) or from the lower respiratory tract when available for viral testing.
• Generally, the findings on chest imaging in COVID-19 are not specific, and overlap with other infections, including influenza, H1N1, SARS, and MERS. Being in the midst of the current flu season, with a much higher prevalence of influenza in the US than COVID-19, further limits the specificity of CT.

Based on these concerns, the ACR recommends:

• CT should not be used to screen for or as a first-line test to diagnose COVID-19.
• CT should be used sparingly and reserved for hospitalized, symptomatic patients with specific clinical indications for CT. Appropriate infection control procedures should be followed before scanning subsequent patients.
• Facilities may consider deploying portable radiography units in ambulatory care facilities for use when CXRs are considered medically necessary. The surfaces of these machines can be easily cleaned, avoiding the need to bring patients into radiography rooms.
• As an interim measure, until more widespread COVID-19 testing is available, some medical practices are requesting chest CT to inform decisions on whether to test a patient for COVID-19, admit a patient, or provide other treatment. The ACR strongly urges caution in taking this approach. A normal chest CT does not mean a person does not have a COVID-19 infection, and an abnormal CT is not specific for a COVID-19 diagnosis. A normal CT should not dissuade a patient from being quarantined or provided other clinically indicated treatment when otherwise medically appropriate. Clearly, locally constrained resources may be a factor in such decision making.

Chest x-ray findings

The CDC does not currently recommend chest CT or CXR as a diagnostic method for COVID-19 infection, so a CXR may not need to be a part of the workup for patients with mild disease. It may, however, be useful if diagnostic ambiguity is present.

CXR findings are nonspecific (Table 7.3). They may show:

• Unilateral or bilateral (more likely) infiltrates;
• Consolidation;
• Multifocal; or
• Pleural effusions (rare).

Table 7.3 Characteristics of the radiographic findings reported by the panel of 11 radiologists who re-read CXRs of COVID-19 patients seen in greater NYC UC Centers from March 9, 2020, to March 24, 2020 (N = 636).¹

Note: Numbers do not add to 100%, as some patients had more than one finding.

References

1. Weinstock MB, Echenique A, Russell JW, et al. Chest x-ray findings in 636 ambulatory patients with COVID-19 presenting to an urgent care center: a normal chest x-ray is no guarantee [published online ahead of print]. J Urgent Care Med. 2020 Apr 13. 
2. Rubin GD, Ryerson CJ, Haramati LB, et al. The role of chest imaging in patient management during the COVID-19 pandemic: a multinational consensus statement from the Fleischner Society [published online ahead of print, 2020 Apr 7]. Radiology. 2020;201365. doi:10.1148/radiol.2020201365
3. Rubin GD, Ryerson CJ, Haramati LB, et al. The role of chest imaging in patient management during the COVID-19 pandemic: a multinational consensus statement from the Fleischner Society [published online ahead of print, 2020 Apr 7]. Radiology. 2020;201365. doi:10.1148/radiol.2020201365
4. Toussie D, Voutsinas N, Finkelstein M, et al. Clinical and Chest Radiography Features Determine Patient Outcomes In Young and Middle Age Adults with COVID-19. [published online ahead of print, 2020 May 14]. Radiology. https://doi.org/10.1148/radiol.2020201754

CT findings

Author: Christopher Sampson, MD, FACEP, Program Director, Emergency Medicine Residency, Assistant Medical Director, MU Emergency Medical Services, Department of Emergency Medicine, Associate Clinical Professor, University of Missouri-Columbia

Ground-glass opacities (GGOs) are the primary finding being seen, based on early literature as well as consolidation. Bilateral findings also appear to be most commonly seen. It appears that GGOs and opacities are more likely an intermediate or late finding in the disease process. Anecdotally, GGOs have been discovered incidentally in patients receiving imaging for other clinical indications.

In one study from China¹ with 121 patients, 22% had no GGOs and no consolidation on chest CT. Of the 94 patients with GGOs, consolidation, or both:

• 34% had only GGOs (with no consolidation); and
• 2% had consolidation in the absence of GGOs.
• The number of lobes affected included:
• 15% with opacities in one lobe;
• 12% with two affected lobes;
• 9% with three affected lobes;
• 15% with four affected lobes;
• 27% with disease affecting all five lobes; and
• 60% with bilateral lung disease.
• The frequency of lobe involvement was:
• 44% right upper lobe;
• 41% right middle lobe;
• 65% right lower lobe;
• 48% left upper lobe; and
• 63% left lower lobe.

In another study from China,² CT images showed:

• Pure GGOs in 77% of patients, including:
• GGOs with reticular and/or interlobular septal thickening in 75% of patients; and
• GGOs with consolidation present in 59% of patients.
• Pure consolidation was present in 55% of patients.
• 86% of patients had bilateral lung involvement;
• 80% involved the posterior part of the lungs; and
• 86% were peripheral.

The authors reported that there were more consolidated lung lesions in patients 5 days or more from disease onset, and patients older than 50 years had more consolidated lung lesions than did those aged 50 years or younger. They also concluded that patients with fever and/or cough and conspicuous GGO lesions in the peripheral and posterior lungs on CT images, combined with normal or decreased white blood cells and a history of epidemic exposure, are highly suspected of having 2019 novel coronavirus (2019-nCoV) pneumonia.

References

1. Bernheim A, Mei X, Huang M, et al. Chest CT findings in coronavirus disease-19 (COVID-19): relationship to duration of infection [published online ahead of print, 2020 Feb 20]. Radiology. 2020;200463. doi:10.1148/radiol.2020200463
2. Song F, Shi N, Shan F, et al. Emerging 2019 novel coronavirus (2019-nCoV) Pneumonia. Radiology. 2020;295(1):210-217. doi:10.1148/radiol.2020200274