Prediction of the Development of Pulmonary Fibrosis Using Serial Thin-Section CT and Clinical Features in Patients Discharged after Treatment for COVID-19 Pneumonia

Abstract

Objective: To identify predictors of pulmonary fibrosis development by combining follow-up thin-section CT findings and clinical features in patients discharged after treatment for COVID-19.

Materials and methods: This retrospective study involved 32 confirmed COVID-19 patients who were divided into two groups according to the evidence of fibrosis on their latest follow-up CT imaging. Clinical data and CT imaging features of all the patients in different stages were collected and analyzed for comparison.

Results: The latest follow-up CT imaging showed fibrosis in 14 patients (male, 12; female, 2) and no fibrosis in 18 patients (male, 10; female, 8). Compared with the non-fibrosis group, the fibrosis group was older (median age: 54.0 years vs. 37.0 years, p = 0.008), and the median levels of C-reactive protein (53.4 mg/L vs. 10.0 mg/L, p = 0.002) and interleukin-6 (79.7 pg/L vs. 11.2 pg/L, p = 0.04) were also higher. The fibrosis group had a longer-term of hospitalization (19.5 days vs. 10.0 days, p = 0.001), pulsed steroid therapy (11.0 days vs. 5.0 days, p < 0.001), and antiviral therapy (12.0 days vs. 6.5 days, p = 0.012). More patients on the worst-state CT scan had an irregular interface (59.4% vs. 34.4%, p = 0.045) and a parenchymal band (71.9% vs. 28.1%, p < 0.001). On initial CT imaging, the irregular interface (57.1%) and parenchymal band (50.0%) were more common in the fibrosis group. On the worst-state CT imaging, interstitial thickening (78.6%), air bronchogram (57.1%), irregular interface (85.7%), coarse reticular pattern (28.6%), parenchymal band (92.9%), and pleural effusion (42.9%) were more common in the fibrosis group.

Conclusion: Fibrosis was more likely to develop in patients with severe clinical conditions, especially in patients with high inflammatory indicators. Interstitial thickening, irregular interface, coarse reticular pattern, and parenchymal band manifested in the process of the disease may be predictors of pulmonary fibrosis. Irregular interface and parenchymal band could predict the formation of pulmonary fibrosis early.

Keywords: COVID-19; Clinical characteristic; Computed tomography; Fibrosis; Follow-up; Prediction.

Fig. 1. Proportion of positive patients for typical imaging features of COVID-19 pneumonia on thin-section CT at different stages.

Pure GGO, GGO with consolidation, interstitial thickening, crazy paving, irregular interface, and parenchymal band are most common CT features in COVID-19 pneumonia. GGO = ground-glass opacity

Fig. 2. Follow-up thin-section CT imaging of 72-year-old man with confirmed COVID-19 pneumonia with fever and muscle aches.

A. First thin-section chest CT scan in our hospital on January 12, 2020 (10 days after symptoms onset). CT imaging shows GGO and little interstitial thickening in bilateral lobes and mainly peripheral sections. B. Three days later, crazy paving is obvious, with also some consolidation. Extent of lesions is increased. C. On January 18, patient was admitted to ICU due to aggravation of disease. CT imaging shows consolidation in bilateral lobes with increased lesion extent. D. On February 8, 5 days after discharge, most lesions are absorbed and parenchymal bands with residual GGO are observed. ICU = intensive care unit

Fig. 3. Typical CT imaging findings of 22-year-old woman with fever.

A. On January 21 (1 day after illness onset), CT imaging shows small region of GGO located in right lower lobe. B. Five days later, extent of lesion is increased, typical features of interstitial thickening and crazy paving are observed. C. Ten days after initial CT imaging, CT imaging shows consolidation with GGO in edge and little parenchymal bands. D. Nine days after discharge during follow-up, all lesions are totally absorbed and there is normal pulmonary parenchyma appearance.