- Patient characteristics
Details of patients’ clinical information were summarized in Table 1. A total of 29 patients (17 males and 12 females) were included in this study. The median age of patients was 56 years (IQR, 47-67). Admission occurred 9 days (IQR, 5-13) after symptom onset. Discharge occurred 27 days (IQR, 21-35) days after symptom onset, and the median in-hospital period was 18 days (IQR, 11-26).
The most common symptoms at illness onset were moderate to high degree of fever (15 moderate fever, 52%; 9 high fever, 31%), dyspnea (20/29, 69%) and dry cough (16/29, 55%). Ten patients (10/29, 35%) had at least one medical comorbidities, and the most common comorbidities were hypertension (7/29, 24%) and hepatitis B infection (5/29, 24%). The median value of blood oxygen saturation on admission was 87% (IQR, 85%-91%). All patients received nasal cannula or/and high-flow mask oxygen therapy.
Laboratory investigations were generally performed once a week in-hospital. Details of laboratory results were summarized in Table 2. The most common abnormalities during hospitalized period were lymphopenia (26/29, 90%), elevated ferritin (26/29, 90%), elevated lactate dehydrogenase (25/29, 86%), and decreased albumin (25/29, 86%).
- Radiological abnormalities on chest CT
Intervals from symptom onset were divided into four stages by interquartile range: stage-1, ≤ 15 days; stage-2, 16-29 days; stage-3, 30-63 days; stage-4, ≥ 64 days. Dynamic patterns of lung abnormalities were analyzed based on the four stages.
Twenty-one patients (21/29, 72%) underwent chest CT scan at stage-1 (≤ 15 days after symptom onset). The median chest CT score was 12 (IQR, 8-15), and predominant patterns in patients were GGO (12/29, 57%), consolidation (6/29, 29%) and crazy-paving (3/29, 14%). Nineteen patients (19/29, 66%) underwent chest CT scan at stage-2 (16-29 days after symptom onset), and lesion progression peaked during this period with a median chest CT score of 13 (IQR, 10-15). Predominant patterns of lung abnormalities were consolidation (11/19, 58%) and GGO (8/19, 42%) (Figure 1).
Follow-up chest CT scans included in stage-3 (30-63 days after symptom onset) mainly described lung abnormalities at a period around one month after discharge, and included 21 patients (21/29, 72%). The median chest CT score decreased to 6 (IQR, 3-11). Four patients (4/21, 19%) in this period revealed complete radiological resolution. Predominant pattern of consolidation (1/21, 5%) decreased, while subpleural parenchymal bands emerged in 6 patients (6/21, 29%). The last follow-up chest CT was performed 66 days (IQR, 61-77) after symptom onset and were mostly included in stage-4 (≥ 64 days after symptom onset). Nineteen patients (19/29, 66%) underwent chest CT scan during this period. Chest CT score continued decreasing to a median of 2 (IQR, 0-3). The most common pattern at last follow-up chest CT were subpleural parenchymal bands (9/19, 47%) and complete radiological resolution (7/19, 37%).
In addition, four patients (4/29, 14%) revealed mild traction bronchiectasis on follow-up chest CT, and 1 patient (1/29, 3%) revealed a small amount of pleural effusion in-hospital which was absorbed at follow-up. Nodules, cystic changes, and lymphadenopathy were rarely presented in this study.
- Dynamic patterns of radiological abnormalities between in-hospital and follow-up chest CT
Comparing lung abnormalities between in-hospital and follow-up chest CT, chest CT scores decreased significantly after discharge from hospital ([13, IQR, 10-16] to [3, IQR, 0-5], P < 0.001). Lung abnormalities revealed by in-hospital chest CT scans were mainly GGO and consolidation. Crazy-paving pattern was presented on chest CT close to admission. Lesion progression occurred in-hospital was presented as increased consolidation from GGO or crazy-paving pattern. On follow-up chest CT scans, which were generally include in stage-3 and -4, patients with consolidation as predominant pattern decreased first and those with GGO in sequence. After discharge, subpleural parenchymal bands increasingly presented as predominant pattern in patients, and was the longest-lasting feature before complete radiological resolution.