Chest X-rays (radiographs) were frequently used during the COVID-19 pandemic to evaluate the lungs of infected patients. This rapid and accessible imaging technique provided a picture of the chest’s internal state, which was useful for managing the large volume of cases. Understanding the characteristic patterns of lung involvement seen on these images helped medical professionals assess the disease’s impact on a patient’s respiratory function.
The Role of Chest X-rays in COVID-19 Care
Chest X-rays played a significant role in the initial management of individuals presenting with symptoms of COVID-19. One of their primary uses was in triage, helping to quickly determine which patients required immediate hospitalization and intensive care resources. By visualizing the extent of disease within the lungs, medical teams could risk-stratify patients and allocate resources efficiently.
Radiologists developed scoring systems to quantify the severity of the infection based on the number of lung zones showing abnormalities. A higher score, indicating more widespread lung involvement, was often associated with a greater likelihood of severe outcomes, such as the need for intubation. X-rays were also used serially to monitor how the disease was evolving, showing if the opacities were worsening, remaining stable, or resolving over time.
Distinctive Features of COVID-19 on X-ray
The lung changes associated with COVID-19 pneumonia present a recognizable pattern on a chest X-ray. The most common finding is hazy, ill-defined areas known as opacities. These opacities represent areas where the tiny air sacs in the lungs, the alveoli, are partially filled with fluid and inflammatory material.
The term “ground-glass opacity” (GGO) is frequently used to describe this appearance, which looks like a veil or frosted glass covering the lung tissue. Lung markings are often still visible through the haze, differentiating it from denser consolidation. These GGOs are often distributed bilaterally, meaning they appear in both the left and right lungs.
The location of these abnormalities commonly favors the peripheral areas of the lungs, close to the chest wall, and the lower lobes. This subpleural distribution, along with the multifocal shape of the opacities, is a strong indicator of COVID-19 viral pneumonia. The severity of the visible changes typically peaks around 10 to 12 days after the onset of symptoms.
Distinguishing COVID-19 Findings from Other Pneumonia
The pattern of COVID-19 pneumonia differs noticeably from the typical presentation of bacterial pneumonia, which helps clinicians in differential diagnosis. Bacterial infections often cause a dense, localized area of consolidation, known as lobar pneumonia, where a whole segment or lobe of the lung appears completely “whited-out” on the X-ray. This consolidation is usually unilateral, affecting only one lung.
In contrast, the viral pneumonia caused by COVID-19 typically produces the more diffuse, patchy, and peripheral ground-glass pattern described previously. Unlike many bacterial infections, COVID-19 X-rays infrequently show an associated pleural effusion, which is a buildup of fluid around the lungs. The bilateral and peripheral nature of the haziness without significant pleural fluid helps to suggest a viral cause over a bacterial one.
Limitations and the Use of CT Scans
Despite their utility, chest X-rays have limitations, particularly early in the course of the infection. The sensitivity of a CXR for detecting COVID-19 pneumonia is lower compared to other diagnostic tools, with studies suggesting it may only detect abnormalities in about 56% to 69% of confirmed cases. A patient can be infected and symptomatic, yet their X-ray may appear completely normal, especially in mild cases.
Computed Tomography (CT) scans offer much higher resolution and sensitivity, ranging from 85% to 98% for identifying lung changes. A CT scan can detect subtle ground-glass opacities that are too faint to be seen on a standard X-ray. For this reason, CT scans were typically reserved for hospitalized patients with complex or uncertain diagnoses, or when a clearer, more detailed assessment of the lung damage was necessary.