[Comparison of Recovery Phase CT Features between Mild/moderate and Severe/critical Coronavirus Disease 2019...

Objective To investigate the computed tomographc(CT)features of mild/moderate and severe/critical cases of coronavirus disease 2019(COVID-19)in the recovery phase. Methods Totally 63 discharged patients in Wuhan,China,who underwent both chest CT and reverse transcription-polymerase chain reaction(RT-PCR)from February 1 to February 29,2020,were included.With RT-PCR as a gold standard,the performance of chest CT in diagnosing COVID-19 was assessed.Patients were divided into mild/moderate and severe/critical groups according to the disease conditions,and clinical features such as sex,age,symptoms,hospital stay,comorbidities,and oxygen therapy were collected.CT images in the recovery phase were reviewed in terms of time from onset,CT features,location of lesions,lobe score,and total CT score. Results There were 37 patients in the mild/moderate group and 26 in the severe/critical group. Compared with the mild/moderate patients,the severe/critical patients had older age [(43±16) years vs. (52±16) years; t=2.10, P=0.040], longer hospital stay [(15±6)d vs. (19±7)d; t=2.70, P=0.009], higher dyspnea ratio (5.41% vs. 53.85%; χ²=18.90, P<0.001), lower nasal oxygen therapy ratio (81.08% vs. 19.23%;χ²=23.66, P<0.001), and higher bi-level positive airway pressure ventilation ratio (0 vs. 57.69%; χ²=25.62, P<0.001). Time from onset was (23±6) days in severe/critical group, significantly longer than that in mild/moderate group [(18±7) days] (t=3.40, P<0.001). Severe/critical patients had significantly higher crazy-paving pattern ratio (46.15% vs.10.81%;χ²=4.24, P=0.039) and lower ground-glass opacities ratio (15.38% vs. 67.57%; χ²=16.74, P<0.001) than the mild/moderate patients. The proportion of lesions in peripheral lung was significantly higher in mild/moderate group than in severe/critical group (78.38% vs.34.61%; χ²=13.43, P<0.001), and the proportion of diffusely distributed lesions was significantly higher in severe/critical group than in mild/moderate group (65.38% vs.10.81%; χ²=20.47, P<0.001). Total CT score in severe/critical group was also significantly higher in severe/critical group than in mild/moderate group [11 (8,17) points vs. 7 (4,9) points; Z=3.81, P<0.001]. Conclusions The CT features in the recovery stage differ between mild/moderate and severe/critical COVID-19 patients.The lung infiltration is remarkably more severe in the latter.