Coronavirus Disease 2019 (COVID-19) Workup

Updated: Jun 12, 2023
  • Author: David J Cennimo, MD, FAAP, FACP, FIDSA, AAHIVS; Chief Editor: Michael Stuart Bronze, MD  more...
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Approach Considerations

Diagnostic testing for SARS-CoV-2 infection can be conducted by the CDC, state public health laboratories, hospitals using their own developed and validated tests, and some commercial reference laboratories. [132]

State health departments with a patient under investigation (PUI) should contact CDC’s Emergency Operations Center (EOC) at 770-488-7100 for assistance with collection, storage, and shipment of clinical specimens for diagnostic testing. Specimens from the upper respiratory tract, lower respiratory tract, and serum should be collected to optimize the likelihood of detection. [113]

The FDA now recommends that nasal swabs that access just the front of the nose be used in symptomatic patients, allowing for (1) a more comfortable and simplified collection method and (2) self-collection at collection sites. [133]

Various organizations, including the CDC, have published guidelines on COVID-19. 

Please see Laboratory Diagnostics and Testing Guidance for COVID-19.



Laboratory Studies

Signs and symptoms of coronavirus disease 2019 (COVID-19) may overlap with those of other respiratory infections; therefore, it is important to perform laboratory testing to specifically identify symptomatic individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). 

Three types of tests may be utilized to determine if an individual has been infected with SARS-CoV-2: 

  • Viral nucleic acid (RNA) detection 
  • Viral antigen detection 
  • Detection of antibodies to the virus  

Viral tests (nucleic acid or antigen detection tests) are used to assess acute infection, whereas antibody tests provide evidence of prior infection with SARS-CoV-2. Home sample collection kits for COVID-19 testing have been available by prescription; in December 2020, the LabCorp Pixel COVID-19 Test Home Collection Kit became the first to receive an FDA EUA for nonprescription use. 

The FDA has advised against the use of antibody tests to ascertain immunity or protection from COVID-19, particularly in patients who have been vaccinated against the disease. According to the agency, differences between antibodies that arise from prior SARS-CoV-2 infection and those induced by vaccination leave the tests unable to determine whether an individual has achieved protection through a vaccine.

Laboratory findings in patients with COVID-19

Leukopenia, leukocytosis, and lymphopenia were common among early cases. [97, 120]  

Lactate dehydrogenase and ferritin levels are commonly elevated. [120]

Wu and colleagues [134] reported that, among 200 patients with COVID-19 who were hospitalized, older age, neutrophilia, and elevated lactate dehydrogenase and D-dimer levels increased the risks for ARDS and death.

Please see Laboratory Diagnostics and Testing Guidance for COVID-19 and COVID-19 Pulmonary Management.


CT Scanning

Chest computed tomography (CT) scanning in patients with COVID-19–associated pneumonia usually shows ground-glass opacification, possibly with consolidation. Some studies have reported that abnormalities on chest CT scans are usually bilateral, involve the lower lobes, and have a peripheral distribution. Pleural effusion, pleural thickening, and lymphadenopathy have also been reported, although with less frequency. [120, 135, 136]

Bai and colleagues reported the following common chest CT scanning features among 201 patients with CT abnormalities and positive RT-PCR results for COVID-19 [137] :

  • Peripheral distribution (80%)
  • Ground-glass opacity (91%)
  • Fine reticular opacity (56%)
  • Vascular thickening (59%)

Less-common features on chest CT scanning included the following [137] :

  • Central and peripheral distribution (14%)
  • Pleural effusion (4.1%)
  • Lymphadenopathy (2.7%)

The American College of Radiology (ACR) recommends against using CT scanning for screening or diagnosis but instead reserving it for management in hospitalized patients. [138]

At least two studies have reported on manifestations of infection in apparently asymptomatic individuals. Hu and colleagues reported on 24 asymptomatic infected persons in whom chest CT scanning revealed ground-glass opacities/patchy shadowing in 50% of cases. [139]  Wang and colleagues reported on 55 patients with asymptomatic infection, two thirds of whom had evidence of pneumonia as revealed by CT scanning. [140]

Progression of CT abnormalities

Li and colleagues recommend high-resolution CT scanning and reported the following CT changes over time in patients with COVID-19 among three Chinese hospitals:

  • Early phase: Multiple small patchy shadows and interstitial changes begin to emerge in a distribution beginning near the pleura or bronchi rather than the pulmonary parenchyma.
  • Progressive phase: The lesions enlarge and increase, evolving to multiple ground-glass opacities and infiltrating consolidation in both lungs.
  • Severe phase: Massive pulmonary consolidations occur, while pleural effusion is rare.
  • Dissipative phase: Ground-glass opacities and pulmonary consolidations are absorbed completely. The lesions begin evolving into fibrosis. [141]

Please see Coronavirus Disease 2019 (COVID-19) Radiologic Images and COVID-19 Pulmonary Management.

Axial chest CT demonstrates patchy ground-glass op Axial chest CT demonstrates patchy ground-glass opacities with peripheral distribution.
Coronal reconstruction chest CT of the same patien Coronal reconstruction chest CT of the same patient above, showing patchy ground-glass opacities.
Axial chest CT shows bilateral patchy consolidatio Axial chest CT shows bilateral patchy consolidations (arrows), some with peripheral ground-glass opacity. Findings are in peripheral and subpleural distribution.

Chest Radiography

In a retrospective study of patients in Hong Kong with COVID-19, common abnormalities on chest radiography, when present, included consolidation (30 of 64 patients; 47%) and ground-glass opacities (33%). Consolidation was commonly bilateral and of lower zone distribution. Pleural effusion was an uncommon finding. Severity on chest radiography peaked 10 to 12 days after symptom onset. [142]

Chest radiography may reveal pulmonary infiltrates. [143]

Please see Coronavirus Disease 2019 (COVID-19) Radiologic Images and COVID-19 Pulmonary Management.

The heart is normal in size. There are diffuse, pa The heart is normal in size. There are diffuse, patchy opacities throughout both lungs, which may represent multifocal viral/bacterial pneumonia versus pulmonary edema. These opacities are particularly confluent along the periphery of the right lung. There is left midlung platelike atelectasis. Obscuration of the left costophrenic angle may represent consolidation versus a pleural effusion with atelectasis. There is no pneumothorax.
The heart is normal in size. There are bilateral h The heart is normal in size. There are bilateral hazy opacities, with lower lobe predominance. These findings are consistent with multifocal/viral pneumonia. No pleural effusion or pneumothorax are seen.
The heart is normal in size. Patchy opacities are The heart is normal in size. Patchy opacities are seen throughout the lung fields. Patchy areas of consolidation at the right lung base partially silhouettes the right diaphragm. There is no effusion or pneumothorax. Degenerative changes of the thoracic spine are noted.
The same patient as above 10 days later. The same patient as above 10 days later.
The trachea is in midline. The cardiomediastinal s The trachea is in midline. The cardiomediastinal silhouette is normal in size. There are diffuse hazy reticulonodular opacities in both lungs. Differential diagnoses include viral pneumonia, multifocal bacterial pneumonia or ARDS. There is no pleural effusion or pneumothorax.