The CO-RADS classification is a standardized reporting system for patients with suspected COVID-19 infection developed for a moderate to high prevalence setting.
CO-RADS 1
- COVID-19 is highly unlikely.
- The CT is normal or there are findings that indicate a non-infectious disease like congestive heart failure, sarcoid, histoplasmosis, malignancy, UIP or fibrotic NSIP (if unchanged to prior examination).
- An exemption has to be made for the first few days of a mild infection when the CT can be normal.
CO-RADS 2
- Level of suspicion of COVID-19 infection is low.
- Findings are consistent with other infections like typical bronchiolitis with tree-in-bud and thickened bronchus walls.
- No typical signs of COVID-19.
CO-RADS 3
- COVID-19 unsure or indeterminate.
- CT abnormalities indicating infection, but unsure whether COVID-19 is involved, like widespread bronchopneumonia, lobar pneumonia, septic emboli with ground glass opacities.
CO-RADS 4
- In CO-RADS 4 the level of suspicion is high.
- Mostly these are suspicious CT findings but not extremely typical:
- Unilateral ground glass
- Multifocal consolidations without any other typical finding
- Findings are suspicious of COVID-19 in underlying pulmonary disease.
CO-RADS 5
- Multifocal GGO and consolidation
- PCR positive
CO-RADS 6
- Patient with positive PCR and bilateral GGO.
