Patient characteristics. A total of 498 patients had been hospitalized for COVID–19 by the end of March 20 2020. 451 patients were excluded due to transfer to other hospitals (204 patients), mild or moderate illness (222 patients), or incomplete data (25 patients). Consequently, 47 patients were included in this study.
Of the included 47 patients, 26 patients were discharged after treatment, whereas 21 patients died from the severe illness. Time from onset of symptoms to discharge or death was 27.4 ± 8.3 (27, 12−50) days or 17.9 ± 7.3 (16, 8−33) days, respectively. Initial symptoms included fever, fatigue, dry cough, expectoration, pharyngalgia, dyspnea, anorexia, myalgia, diarrhea, nausea and vomiting. Table 1 summarizes the baseline characteristics and clinical syndromes of patients with severe COVID–19 based on prognosis. The dead patients showed significant increases in age, comorbidities (cerebrovascular disease, diabetes mellitus and chronic kidney disease) and clinical syndromes (sepsis and septic shock) compared with the discharged patients (P <.05). In addition, the dead patients showed significant decreases in lymphocyte count (P <.001), CRP (P <.001), ALT (P <.001) and SpO2 level (P <.001) compared with the discharged patients at baseline. Changes of CT abnormalities.The indications for serial scans included initial diagnosis, clinical deterioration and requirement of a change in treatment. The mean number of CT scans was 3.3 ± 1.2 (3, 2−6) per patient. The mean time from onset of symptoms to the first CT scan was 4.9 ± 3 (5, 0 −13) days, and the mean time from the last CT scan to discharge or death was 3.3 ± 2.3 (3, 0 −10) and 5.6 ± 4 (5, 0−18) days, respectively.
There were apparent changes of CT abnormalities in patients with severe COVID–19 during the hospitalization. In the 26 discharged patients, the total CT score markedly increased during the first two weeks after onset of symptoms, with a median peak CT score of 10 (range, 5−21), and then it dropped slowly to a median CT score of 8 (range, 3−15) in the fourth week or longer (Fig. 1).
The predominant abnormalities were ground-glass opacity and opacification within the first week, followed by coexistence of 4 patterns during the second week, after which the pattern appeared as ground- glass, reticular or mixed patterns (Fig. 2A). The frequency of the ground-glass pattern (Figs. 3 and 4) was highest in the first week (79.2%, 19/24) and maintained a high proportion in the second week (45.5%, 15/33), after which it decreased. Superimposed interlobular and intralobular septal thickening ( Fig. 4B) were frequently observed in the first 2 weeks and superimposed irregular linear opacities (Fig. 4C) became more common thereafter. Consolidation pattern was not common, with a frequency of 16.7% (4/24), 15.2% (5/33) and 4% (1/25) in the first, second and third week, respectively, although consolidation was frequently noted in combination with other abnormalities. Reticular pattern (Fig. 3C) was found from the second week (6.1%, 2/33) and became more common in the third (20%, 5/25) week and fourth week or longer (45.8%, 11/24). Mixed pattern (Fig. 4D) was noted from the second week and maintain high proportions in the second (33.3%, 11/33) week and the third week (44%, 11/25), after which it decreased (29.2%, 7/24). In terms of the longitudinal changes of abnormalities, the initial CT scans demonstrated predominant ground-glass opacities, consolidation, mixed pattern and normal findings in 20, 4, 1 and 1 patients, respectively. Of the 20 patients with ground-glass opacities on the initial scans, 10 developed a reticular pattern, 8 developed a mixed pattern, and 2 decreased in extent before discharge. Of the 4 patients with consolidation on the initial scans, 2 developed a ground-glass opacity pattern, 1 developed a reticular pattern, and 1 developed a mixed pattern. The patient with mixed pattern on the initial scan revolved completely, and the patient with normal findings developed a reticular pattern. Of note, the reticular and mixed pattern generally occurred in the background of the original ground-glass opacities or consolidation and may persist until discharge (Figs. 3 and 4).
The distribution of opacities also varied with time (Fig. 5A). Subpleural distribution (Fig. 4A) was predominant in all the weeks, with proportions of 42.4%−66.7%. Random distribution (Fig. 3A) was noted with a low frequency in all the weeks. Diffuse distribution (Fig. 4B) was occasionally noted in the first week (8.3%, 2/24) and become more common in the second week (39.4%, 13/33), after which it decreased. Thirteen patients presented with pleural thickening adjacent to the lung abnormalities. Seven patients developed mild to mediate pleural effusion, one of whom developed concomitant pericardial effusion. Two patients developed subsegmental atelectasis, which appeared as parenchymal bands and was reversed with inflammation resolution. No pneumothorax, pneumomediastinum or mediastinal lymphadenopathy was noted.
In contrast, the 21 dead patients showed different CT features (Fig. 6). The median CT score was progressively increased from 9 (rang, 1−19) in the first week to 19.5 (rang, 19−20) in the fourth week (Fig. 1). The predominant patterns of abnormality only included ground-glass opacity and consolidation. Ground- glass opacity pattern was more common than consolidation pattern during the first 3 weeks, and thereafter the two patterns were found in equal proportions (Fig. 2B). Opacities were predominantly distributed in the subpleural regions (48.3%, 14/29) during the first week and became more diffuse (69.2%, 9/13) in the second week, after which opacities were only found displaying a diffuse pattern (Fig. 5B). Pleural thickening and pleural effusion were found in 4 and 7 patients, respectively. Pneumomediastinum was noted in 1 patient late in the course (Fig. 6C).
Comparison of CT changes in discharged and dead patients. Given the length of hospital stay, the distribution of time to CT scan and the CT findings, the CT changes was compared in discharged and dead patients on the bases on scans of three time periods: within the first week, within the second week, and from the third week onwards. Table 2 summarizes the temporal change in CT score, abnormality pattern and opacity distribution between the two groups of patients. CT scores of the death group were significantly higher than those of the discharge group within the first week (9 vs. 6, P
= .014), the second week (14 vs. 10, P = .042) and from the third week (19 vs. 9, P <.001). There were significant differences in abnormality pattern between two groups within the second week ( P = .029) and from the third week (P <.001). Mixed and reticular patterns were noted in charged patients during the second week or longer, whereas they were not found in dead patients. Significant differences were also noted in opacity distribution between the two groups from the third week ( P <.001). Subpleural and random distribution were more prevalent in discharged patients, whereas diffuse distribution achieved a dominant proportion in death group from the third week onwards.