• Jinfeng Gu, Li Yang, Tao Li, Ye Liu, Jing Zhang, Kejia Ning, and Dajian Su.
• Department of Radiology, The Second Hospital in Fuyang, Fuyang, Anhui, China.
• Eur Radiol. 2021 Mar 1; 31 (3): 1175-1184.

ObjectiveTo determine CT's role in the early detection of COVID-19 infection and serial CT changes in the disease course in patients with COVID-19 pneumonia.MethodsFrom January 21 to February 18, 2020, all of the patients who were suspected of novel coronavirus infection and verified by RT-PCR tests were retrospectively enrolled in our study. All of the patients underwent serial RT-PCR tests and serial CT imaging. The temporal relationship between the serial RT-PCR results (negative conversion to positive, positive to negative) and serial CT imaging was investigated, and serial CT changes were evaluated.ResultsA total of 155 patients with confirmed COVID-19 pneumonia were evaluated. Chest CT detection time of COVID-19 pneumonia was 2.61 days earlier than RT-PCR test (p = 0.000). The lung CT improvement time was significantly shorter than that of RT-PCR conversion to negative (p = 0.000). Three stages were identified from the onset of the initial symptoms: stage 1 (0-3 days), stage 2 (4-7 days), and stage 3 (8-14 days and later). Ground glass opacity (GGO) was predominant in stage 1, then consolidation and crazy paving signs were dramatically increased in stage 2. In stage 3, fibrotic lesions were rapidly increased. There were significant differences in the main CT features (p = 0.000), number of lobes involved (p = 0.001), and lesion distribution (p = 0.000) among the different stages.ConclusionChest CT detected COVID-19 pneumonia earlier than the RT-PCR results and can be used to monitor disease course. Combining imaging features with epidemiology history and clinical information could facilitate the early diagnosis of COVID-19 pneumonia.Key Points• The chest CT detection time of COVID-19 pneumonia was 2.61 days earlier than that of an initial RT-PCR positive result (t = - 7.31, p = 0.000). • The lung CT improvement time was significantly shorter than that of RT-PCR conversion to negative (t = - 4.72, p = 0.000). • At the early stage (0-3 days), the CT features of COVID-19 were predominantly GGO and small-vessel thickening; at stage 2 (4-7 days), GGO evolved to consolidation and crazy paving signs. At stage 3 (8-14 days and later), fibrotic lesions significantly increased, accompanied by consolidation, GGO, and crazy paving signs.

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