Chest X-ray and CT Scan for COVID-19

Studies from China suggest that chest radiographs (X-rays) and chest computed tomography (CT) scans can help diagnose the disease. Both can reveal abnormalities indicative of lung disease, including COVID-19.

X-ray

A chest X-ray (radiograph) is the most commonly ordered imaging study for patients with respiratory complaints. In a patient's early stages of COVID-19, a chest X-ray may be read as normal. In patients with severe disease, X-ray readings may resemble pneumonia or acute respiratory distress syndrome (ARDS).

Importantly, these findings are not specific for COVID-19 and may overlap with those of other infections. Doctors cannot make a confident diagnosis of COVID-19 on the basis of chest X-ray alone.

Chest X-ray findings of COVID-19 disease include:

• Bilateral multifocal consolidations that may progress to involve entire lungs: The term "consolidation" refers to the filling of pulmonary airspaces with fluid or other products of inflammation. The phrase "bilateral multifocal" means that the abnormalities occur in different locations in both lungs.
• Small pleural effusions: This is abnormal fluid that develops in the spaces around the lungs.

CT Scan

Also referred to as a CAT scan, a CT scan of the chest is a specialized type of imaging study which uses X-rays to create 3D images of the chest. Chest CT is more effective than chest X-ray in the detection of early COVID-19 disease.

However, up to 50% of patients may have a normal chest CT within the first two days after the onset of symptoms. Also, other types of pneumonia may mimic COVID-19 on chest CT.

Nevertheless, suspicious findings on chest CT are a valuable clue (along with the clinical presentation and exposure history) that a patient may have COVID-19.

Chest CT findings of COVID-19 disease include:

• Multifocal ground-glass opacities and consolidations: The term "ground-glass opacity" refers to the hazy appearance of the lungs on imaging studies, almost as if sections are obscured by ground glass. It may be due to the filling of pulmonary airspaces with fluid, the collapse of the air spaces, or both.
• Location: Abnormalities tend to occur in the peripheral and basal areas of the lungs, more commonly in the posterior lung bases.

CT Scan and Swab Test

The most reliable test for the diagnosis of SARS-CoV-2 infection is an oropharyngeal or nasopharyngeal polymerase chain reaction (PCR) assay, involving a throat swab or a swab of the place where the back of the nose meets the throat.

In this test, a sample is collected and tested for viral RNA. There are very few false positives with this test. However, some reports have suggested a sensitivity of between 60% and 70%, meaning that there may be a significant number of infected people who actually have a negative test.

Multiple tests are unlikely to be done if the first test is negative. But if a patient's condition gets worse, a second test may be done to confidently rule out infection.

Some reports from China have suggested that, in some patients with COVID-19 pneumonia, abnormalities on chest CT may appear despite negative swab tests. This finding, combined with the initial lack of sufficient test kits, has led some medical practices to request chest CTs to screen patients for the disease.

Doctors know to be cautious about this approach. They realize that chest CT may look normal in patients with early disease. Also, the CT abnormalities of COVID-19 may appear similar to those of other infections.

Summary

Researchers are exploring whether X-ray, CT scans, and CT scans and swab tests can help healthcare providers diagnose COVID-19. For now, the results are mixed: Doctors cannot make a confident diagnosis of COVID-19 with chest X-ray alone. The test could miss early-stage COVID-19 while producing results that resemble other conditions (like pneumonia) in more advanced cases. Chest CT is more effective than chest X-ray. But the most reliable test for an accurate diagnosis is an oropharyngeal or nasopharyngeal polymerase chain reaction (PCR) assay, involving a throat swab or a swab of the place where the back of the nose meets the throat.

A Word From Verywell

The COVID-19 pandemic has thrust an enormous responsibility on public health authorities. They must comb through the newest and most reliable data to set policies that limit mortality, curtail disease transmission, protect healthcare workers, and allow the continued function of the healthcare system.

The available data changes rapidly as the scientific community learns more about COIVD-19. No one is comfortable with uncertainty. But it is best to follow the recommendations set by groups like the CDC, whose guidelines are supported by the most solid evidence available.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.