Routine screening CT for the identification of COVID-19 pneumonia is currently not recommended by most Radiologic Societies (Italian Society of Medical and Interventional Radiology, American College of Radiology , Royal College of Radiologists , Royal Australian and New Zealand College of Radiology reports  and Canadian Association of Radiologists ) that declare that “CT never can be used in screening programs and that CT as any other diagnostic methods, cannot predict Covid-19 onset”.
Moreover, Zhiliang et al , reported that the 29.2% of patients those COVID-19 positive closed contacts never developed any symptoms or changes on chest CT. The remainder presented changes on CT, but only 21% developed symptoms during their hospital course and none of them developed severe disease. This suggests that a high percentage of COVID-19 carriers are asymptomatic. In 112 cases with confirmed COVID-19 diagnosis at RT-PCR, chest CT images of asymptomatic and symptomatic patients among the passengers and crew of the Diamond Princess cruise ship were analyzed. Of the asymptomatic cases, 54% showed CT signs of pneumonia while 80% of the symptoms had positive CT. Asymptomatic patients tended to show patterns with predominant appearance of the GGO while symptomatic patients tended to have lung thickenings more frequently .
Several publications have described CT imaging features in patients affected by COVID-19, the evolution of these features over time, and the radiologists performance to differentiate COVID-19 from other viral infections [12, 20, 22, 28]. These studies have shown that COVID-19 often occurs on CT images with peripheral ground-glass opacities (GGO) and nodular or mass-like GGO with a distribution bilateral and multilobar. . Guan et al  showed that the most common chest CT patterns were ground-glass opacity (56.4%) and bilateral patchy shadowing (51.8%).
However, additional imaging findings have been reported including linear, curvilinear or perilobular opacities, consolidation and diffuse GGO, which can mimic various pathological processes such as other infections, inhalational exposures, and drug toxicities [31-32]. Moreover, Valente et al  evidenced the importance to report also the incidental findings, not linked to the pneumonia, including peripheral pulmonary artery aneurysms or incidental pulmonary nodules.
The first report of patients with COVID-19 described bilateral lung involvement on initial chest CT in 40 of 41 patients, with a consolidative pattern seen in patients in the Intensive Care Unit (ICU) and a predominantly ground-glass pattern in patients who were not in the ICU . An investigation in 21 individuals with confirmed COVID-19 described abnormal findings in 86% of chest CT, with bilateral lung involvement in 88.9% . Multifocal GGO and consolidations were reported in 57% and 29%, respectively, with a peripheral lung tendency .
Some studies reported that chest CT findings can precede positivity on reverse transcriptase polymerase chain reaction testing (RT-PCR). In the present study, CT findings resulted positive for viral pneumonia in 126 of 134 (94.0%) patients while COVID-19 was diagnosed at RT-PCR in 104 of them (77.6%); the difference between two COVID-19 prevalence rate in this cohort was statistically significant. These results were according to literature reporting that RT-PCR sensitivity ranges from 42% to 71% [34, 35], and that an initially negative RT-PCR may take up to 4 days to convert in a patient with positive COVID-19 diagnosis . The reported sensitivities and specificities of CT for COVID-19 vary widely (60 to 98% and 25% to 53%, respectively)[34-38], probably related to the studies retrospective nature, including lack of strict diagnostic imaging criteria and procedural to confirm the infection. The CT positive and negative predictive value for COVID-19 diagnosis are estimated at 92% and 42%, respectively, in a population with high pretest disease probability . Ai et al  reported that the sensitivity of chest CT in suggesting COVID-19 was 97% based on positive RT-PCR results. In patients with negative RT-PCR results, 75% (308/413) had positive chest CT findings; the specificity, PPV, NPV and accuracy reported were 25%, 65%, 83% and 68% respectively. The relatively low negative predictive values reported in these studies [36-37] suggests that CT may not be an adequate COVID-19 screening test in earlier stages of the disease and the relatively low positive predictive values suggests that CT may not be a valid decision making. Furthermore, the safe use of CT to study COVID-19 patients is logistically demanding and can overwhelm the available resources. Even with proper cleaning protocols, healthcare professionals and CT scanners could become infection vectors for other vulnerable patients requiring imaging.
The goal of structured reporting in the setting of COVID-19 pneumonia is to provide a standardized language in the description of the CT findings decreasing reporting variability allowing the immediacy of the report, reducing waiting times, facilitating the understanding of the result also by other specialists, reducing the uncertainty in reporting findings potentially attributable to this infection, thereby allowing better integration into clinical decision making. While we do not currently recommend the use of CT screening for COVID-19 pneumonia, we suggest using a standardized language when specifically asked to address whether or not findings of COVID-19 pneumonia may be present on CT images and propose language that could be placed in the impression of the report.
The use of structured report allowed to identify the main CT features and to calculate the percentages of presence in this cohort of 134 patients subjected to CT scan at time of the admission. Our results, according to the recent literature, showed that the disease predominantly affects multiple lobes without any lobar prevalence. Multifocal areas of GGO, with or without consolidations (96.8%), were the main CT features in patients with COVID-19 infections. GGOs were predominantly bilateral (89.3%) with peripheral (80.3%) and patchy (70.5%) distribution. Consolidation disease was predominantly bilateral (83.9%) with peripheral (87.1%) and segmental (47.3%) distribution. Moreover, we noted additional significant CT signs of COVID-19 infection such as crazy-paving pattern, seen in 75.4% of patients with a significant p value (<<0.001); septal thickening seen in 37.3% of patients, air bronchogram sign in 39.7% of patients and “reversed halo” sign in 23.8% of cases. Discrete pulmonary nodules, increased trunk diameter of the pulmonary artery, pleural effusion can be found but in a low non-significant percentage of cases (7.9%, 6.3%, 14.3%, respectively). The pericardium effusion reported in and 16.7% of patients could determine cardiac injury that is a common condition among patients hospitalized with COVID-19, associated with higher risk of in-hospital mortality, as reported by Shi et al . Barotrauma sign was absent in all the patients. In this cohort, differently from what is reported in the literature [20, 24], high percentage of the patients suspicious for COVID-19 had mediastinal lymphadenopathy greater than 1 cm in short axis diameter (54.8%).
The main limitation of the present study is the nature retrospective and monocentric of the study conducted on a cohort of symptomatic hospitalized patients from an area of high epidemiological risk and with a high pre-test probability of COVID-19 infection.
In conclusion, the use of a structured report could support the management  of interstitial pneumonia from Covid-19 identifying the cardinal hallmarks of Covid-19 infection on imaging represented by bilateral, multifocal ground-glass opacities with peripheral and patchy distribution and bilateral consolidations with prevalent peripheral and segmental distribution. Other greater CT findings such as “crazy-paving” pattern, septal thickening, air bronchogram and “reversed halo” sign must be listed.
- GGO opacities and consolidations were the two main signs of COVID-19 lesions on CT images.
- GGOs were predominantly bilateral with a peripheral and multifocal/patching
- Consolidation disease was predominantly bilateral, peripheral and
Required Summary Statement
The use of a structured report could support the management of interstitial pneumonia from Covid-19 identifying the cardinal hallmarks of Covid-19 infection on imaging.