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Table 1 CO-RADS categories

From: Comparison of the CO-RADS and the RSNA chest CT classification system concerning sensitivity and reliability for the diagnosis of COVID-19 pneumonia

CO-RADS Level of suspicion CT findings
CO-RADS 1 Very low Normal or non-infectious, e.g. emphysema
CO-RADS 2 Low Findings consistent with infections other than COVID-19, e.g. tree-in-bud
CO-RADS 3 Equivocal Equivocal findings for pulmonary involvement of COVID-19 based on CT features that can also be found in other viral pneumonia or non-infectious causes, e.g
  Perihilar GGO
  Homogenous extensive GGO with or without sparing of some secondary pulmonary lobules
  GGO together with smooth interlobular septal thickening with or without pleural effusion in the absence of other typical CT findings
  Small GGO that are not centrilobular or not located close to the visceral pleura
  Patterns of consolidation compatible with organizing pneumonia without other typical findings of COVID-19
CO-RADS 4 High Findings suspicious for COVID-19 but not typical, e.g. unilateral GGO, multifocal consolidations only
CO-RADS 5 Very high Typical for COVID-19, e.g. multifocal GGO, peripheral and basal distribution, GGO and consolidations, crazy paving, reversed halo, spider web sign
  1. CO-RADS COVID-19 Reporting and Data System, CT computed tomography, COVID-19 coronavirus disease 2019, GGO ground-glass opacities