Table 5 Overview of the COVID-19 reporting and data system categories (CO-RADS) [8]

CO-RADS 1

Highly unlikely

Normal or non-infectious such as malignancy, congestive heart failure, and sarcoidosis

CO-RADS 2

Very low

Typical for infections that are incompatible with COVID-19 pneumonia, such as bronchitis, bronchiolitis, bronchopneumonia with patchy opacities, and pulmonary abscess. Features include tree-in-bud sign, centrilobular nodular pattern, lobar or segmental consolidation, and lung cavitation

CO-RADS 3

Indeterminate

Findings can be compatible with various viral pulmonary infections, including COVID-19 pneumonia, like widespread bronchopneumonia consolidations with GGO

CO-RADS 4

High

Similar to those found in CO-RADS 5 but are not located in contact with the pleura or located unilaterally. This category also encompasses multifocal consolidations without any other typical findings

CO-RADS 5

Very high

Multifocal bilateral GGO with or without consolidations, close to the pleura / the interlobar fissures. Rounded and unsharp demarcated GGO and sharply delineated GGO outlining the secondary pulmonary lobules, indicating early involvement of the lungs

The “crazy paving” pattern appears later in the course of the disease, with visible interlobular lines and increasing consolidations within the GGO areas

Opacities resembling organizing pneumonia, reverse halo sign and GGO with subpleural consolidations in the late course of the disease. Subpleural bands with thickened vessels