The coronavirus pandemic has filled our vocabularies with more medical terms than most of us would ever hear about otherwise: flattening the curve, active and passive immunity, PPE.
Another—ground glass opacities, referring to findings on computed tomography (CT) scans of COVID-19 patients—has also been in the news lately, with reports showing that those specific findings on patient's scans can help diagnose and monitor coronavirus infections.
While it's important to note that ground glass opacities aren't specific to COVID-19, meaning they can show up in other conditions and infections, they are common among those with coronavirus. Here's what you need to know.
What are ground glass opacities?
According to Isabel Oliva Cortopassi, MD, chief of thoracic imaging at Yale Medicine and an associate professor of radiology and biomedical imaging, ground glass opacities (GGOs, for short) indicate abnormalities in the lungs. "Ground glass opacities [are] a pattern that can be seen when the lungs are sick," says Dr. Cortopassi. She adds that, while normal lung CT scans appear black, an abnormal chest CT with GGOs will show lighter-colored or gray patches.
Those lighter patches don't completely obscure the other structures in the lungs, says Jennifer Possick, MD, a Yale Medicine pulmonologist—that makes them different from lesions associated with lung cancer, which can often appear as solid. With GGOs, "there is haziness seen overlying an area of the lung, but the underlying structures of the lung (airways, blood vessels, lung tissue) can still be identified," she says. It resembles, well, ground glass, or glass that is still transparent but has a matte finish.
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What do ground glass opacities indicate?
It's important to keep in mind that GGOs aren't specific to COVID-19 and can be seen in so many different settings, says Dr. Possick. GGOs in chest CT scans can also indicate congestive heart failure, inflammatory interstitial lung diseases, and diffuse alveolar hemorrhage (bleeding into the airspaces of the lungs), among other issues. But one of the most common diagnosis for GGOs is viral pneumonias, most often caused by respiratory syncytial virus (RSV), cytomegalovirus, herpes simplex virus, and coronavirus.
In terms of COVID-19, Dr. Cortopassi explains GGOs on a CT scan are indicative of COVID-19-related pneumonia, or lung inflammation caused by the viral infection. (It's important to note, however, that not all patients with COVID-19 will go on to develop pneumonia, says Dr. Cortopassi.)
Researchers from the University of Michigan reported on the prevalence of GGOs in chest imaging among COVID-19 patients in a new case series published in the journal Radiology: Cardiothoracic Imaging. Looking at three different cases of confirmed COVID-19 patients in China, researchers discovered GGOs in each patient's CT scan. Those findings, according to the researchers, show that "in the context of a travel history or exposure, the presence of nodular and peripheral ground glass opacities should alert the radiologists to [the possibility]" of a COVID-19 diagnosis.
Another study published in the journal Radiology found that, among 51 Chinese patients with confirmed COVID-19 pneumonia, GGOs showed up in the chest CT scans of 77% of patients. And original research from scientists in China, also published in Radiology, found that CT scans were able to find 97% of COVID-19 infections overall, while blood tests were only able to correctly identify 59% of cases.
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While GGOs are some of the most common findings seen in patients with COVID-19-related pneumonia, Dr. Cortopassi points out that there are additional imaging appearances that can signal it as well—including consolidation (a white portion on a lung CT that signifies fluid is present) and septal thickening (a thickening of the connective tissues within the lung, also indicative of fluid, fibrous tissue, or cell infiltration). “These are terms we radiologists use to describe what we see when reading a chest CT and are not specific for one disease,” she adds.
These terms are important to know, especially if the words "ground glass opacities" ever come out of your doctor's mouth. But Dr. Corotpassi reiterates that a COVID-19 diagnosis doesn't automatically lead to a worsened condition in which these GGOs will show up in a CT scan, nor does an abnormal scan definitively mean a coronavirus infection. "Some people will have completely different radiologic findings, and some people will have no imaging abnormalities at all," she says.
As always, however, if you are experiencing symptoms of COVID-19—dry cough, fever, shortness of breath, fatigue—it's best to call your doctor or other health care professional for a telemedicine evaluation (don't go directly to the ER or your doctor's office, otherwise you risk infecting others or yourself). Your doctor can then determine whether you should be tested for COVID-19 and can help you figure out next steps on your way to a possible diagnosis.
The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.
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