CO-RADS (COVID-19 Reporting and Data System)

As per research studies, typical features of COVID-19 seen on CT scans: 

• Ground-glass opacities or areas
• Crazy paving (described as visible intralobular lines)
• Patterns compatible with pneumonia
• Thickened vessels within abnormalities

Following are each of the categories are what they mean for the patient:

CO-RADS Category 0

CO-RADS category 0 is assigned when the CT scan was incomplete or not technically sufficient enough for assigning any of the other scores. Ideally, the scan should be repeated for an accurate score.

CO-RADS Category 1

In category 1, the level of suspicion of pulmonary involvement is considered to be very low. In cases assigned category 1, either the CT scan results were normal or they showed abnormalities that could be attributed to non-infectious diseases such as mild to severe emphysema, perifissural nodules, lung tumors or fibrosis.

CO-RADS Category 2

In category 2, the level of suspicion of pulmonary involvement with COVID-19 is considered to be low. In cases assigned this category, the CT results could indicate another infection besides COVID-19, like bronchitis, infectious bronchiolitis, bronchopneumonia, lobar pneumonia and pulmonary abscess.

CO-RADS Category 3

In category 3, the level of suspicion of pulmonary involvement with COVID-19 is considered to be unsure, as the CT results, which may show ground-glass opacities (typical for COVID-19 affected lungs), could indicate pulmonary involvement by COVID-19 but also other conditions, such as other viral pneumonia or non-infectious diseases of the lungs.

CO-RADS Category 4

In category 4, the level of suspicion on pulmonary involvement with COVID-19 is considered to be high due to the abnormalities shown in the images. If assigned this category, it would mean that the CT results are typical for a COVID-19 positive patient but there is a slight overlap still with other types of viral pneumonia as there are some classic features that are placed atypically on the images - this is what differentiates it from Category 5.

(Read more: Lung infections)

CO-RADS Category 5

In category 5, the level of suspicion of pulmonary involvement with COVID-19 becomes very high. Ground glass opacities are noted in the CT scans, with or without consolidation, closer to the visceral pleura (a membrane surrounding the lungs) than in the categories before this. There are three different patterns that may be noted on the images, which confirm the stage of the disease.

CO-RADS Category 6

Category 6 is for confirmed cases of COVID-19 infection through an RT-PCR test.

(Read more: COVID-19 and pregnancy)