Stages of COVID-19 on chest CT
| Early stage (0–2 days) |
| Approximately 50% of patients have negative chest CT |
| The remaining have ground-glass opacities (44%) and consolidation (17%), more often unilateral |
| The less pulmonary consolidation identified on CT, the greater the probability of initial negative reverse transcriptase polymerase chain reaction results11 |
| Intermediate stage (3–5 days) |
| 9% of patients have negative chest CT |
| 88% have ground-glass opacities with or without crazy paving (a sign of progression or peak stage), and 55% have consolidation (bilateral in 76%, peripheral in distribution in 64% with rounded morphology)12 |
| Late phase (6–12 days) |
| Most patients have positive CT findings |
| Progressive consolidation, evolving linear consolidation, and organizing pneumonia |
| Reverse-halo appearance (a sign of healing or evolving lesion)12 |
| Ground-glass opacities in 88% with or without crazy paving |
| Severe phase |
| Massive pulmonary consolidation and “white lungs” |
| Recovery phase |
| Parenchymal abnormalities resolve with residual linear opacities (Figure 6) |
Based on information from references 5 and 11–14.