**5.2 Chest CT**

Although chest computed tomography (CT) may be more sensitive than chest radiograph and some chest CT findings may be characteristic of COVID-19, no finding can completely rule in or rule out the possibility of COVID-19. Chest CT in patients with COVID-19 most commonly demonstrates ground-glass opacification with or without consolidative abnormalities, consistent with viral pneumonia. In a systematic review of studies evaluating the chest CT findings in over 2700 patients with COVID-19, the following abnormalities were noted: Ground-glass opacifications, Ground-glass opacifications with mixed consolidation, adjacent pleural thickening, Interlobular septal thickening, Air bronchograms. Other less common findings were a crazy paving pattern (ground-glass opacifications with superimposed septal thickening), bronchiectasis, pleural effusion, pericardial effusion, and lymphadenopathy. Chest CT abnormalities in COVID-19 are often bilateral, have a peripheral distribution, and involve the lower lobes.

Although these findings are common in COVID-19, they are not unique to it and are frequently seen with other viral pneumonias.

As with chest radiographs, chest CT may be normal soon after the onset of symptoms, with abnormalities more likely to develop over the course of illness. However, chest CT abnormalities have also been identified in patients prior to the development of symptoms and even prior to the detection of viral RNA from upper respiratory specimens. Among patients who clinically improve, resolution of radiographic abnormalities may lag behind improvements in fever and hypoxia.
