One-year follow-up CT findings in COVID-19 patients: A systematic review and meta-analysis

Coronavirus disease 2019 (COVID-19) often causes radiological and functional pulmonary sequelae. However, evidence on 1-year follow-up of pulmonary sequelae is limited. We aimed to investigate the characteristics and time-course of pulmonary sequelae after recovery from COVID-19 through 1-year follow-up. We searched PubMed and EMBASE databases on 25 February 2022, and included studies with computed tomography (CT) findings at the 1-year follow-up. The extracted data on CT findings were analysed using a one-group meta-analysis. We further analysed the data in relation to COVID-19 severity, improvement rate and lung function. Fifteen eligible studies (N = 3134) were included. One year after COVID-19, 32.6% (95% CI 24.0-42.6, I²  = 92.9%) presented with residual CT abnormalities. Ground-glass opacity and fibrotic-like changes were frequently observed in 21.2% (95% CI 15.4-28.4, I²  = 86.7%) and 20.6% (95% CI 11.0-35.2, I²  = 91.9%), respectively. While the gradual recovery was seen on CT (52.9% [mid-term] vs. 32.6% [1 year]), the frequency of CT abnormalities was higher in the severe/critical cases than in the mild/moderate cases (37.7% vs. 20.7%). In particular, fibrotic changes showed little improvement between 4-7 months and 1 year after COVID-19. Pulmonary function tests at 1 year also showed the decline in diffusing capacity of the lung for carbon monoxide, especially in severe/critical cases. Our meta-analysis indicated that residual CT abnormalities were common in hospitalized COVID-19 patients 1 year after recovery, especially fibrotic changes in severe/critical cases. As these sequelae may last long, vigilant observations and longer follow-up periods are warranted.