Longitudinal Assessment of Pulmonary Involvement and Prognosis in Different Subtypes of COVID-19 Patients After One Year Using Low-Dose CT: A Prospective Observational Study

Abstract

Rationale and objectives: Severe COVID-19 typically results in pulmonary sequelae. However, current research lacks clarity on the differences in these sequelae among various clinical subtypes. This study aimed to evaluate the changing lung imaging features and predictive factors in patients with COVID-19 pneumonia in northern China over a 12-month follow-up period after the relaxation of COVID-19 restrictions in 2022.

Materials and methods: Imaging and clinically relevant data from three groups (moderate, severe, and critical) of patients with varying severity were prospectively analyzed. Low-dose CT scans were conducted at 3, 6, and 12 months after discharge, with chest CT images evaluated at baseline and each follow-up using qualitative and quantitative analyses. Clinical symptoms and pulmonary function recovery at 12 months were documented. The correlation between lung function and CT results was analyzed. Univariate and multivariable logistic regression analyses were employed to examine factors influencing prognosis, while a post-hoc analysis model was utilized to investigate the relationships among different groups, time points, and chest CT findings.

Results: Among the 103 hospitalized patients with COVID-19 pneumonia, 64 completed the 12-month evaluation. The median age was 63.70 ± 12.15%, and 62.5% (40/64) were men. During the follow-up period, while 67.19% (43/64) showed abnormalities, including fibrotic changes in 9.38% (6/64). Multivariable logistic regression identified age ≥ 65 (OR: 8.66; 95% CI: 1.86, 40.34; P = 0.006), length of hospital stays (OR: 1.23; 95% CI: 1.03, 1.47; P = 0.022), and baseline consolidation volume as a percentage of the whole lung (OR: 56.95; 95% CI: 1.198, 2706.782; P = 0.04) as independent risk factors for persistent CT lung abnormalities at 1 year. After 1 year, 34.38% (22/64) of patients still had abnormal lung function, and 9.38% (6/64) had pulmonary fibrosis and restrictive ventilatory dysfunction. The relationship between lung function and CT findings is weak correlation. The mixed model analysis revealed significant differences between groups, particularly between the moderate and severe groups, and significant changes in CT values over time.

Conclusion: One year after infection, more than one third of even moderate patients with mild symptoms had persistent pulmonary abnormalities. In our study, fibrotic changes were seen in severe and critically ill patients and remained stable 6 months after discharge from hospital. Imaging parameters can predict the prognosis. The larger the extent of baseline consolidation, the worse the prognosis of elderly patients.

Keywords: COVID-19; Chest CT Imaging; Lung Function; Pulmonary Fibrosis.