Background: The coronavirus disease 2019 (COVID-19) causes a wide spectrum of lung manifestations ranging from mild asymptomatic disease to severe respiratory failure. Recently, it has been suggested that respiratory damage remains for a long time after recovery from COVID-19. We aimed to clarify the characteristics of radiological and functional lung sequelae of COVID-19 patients described in follow-up period.
Methods: PubMed and EMBASE were searched on October 20th, 2020 to investigate characteristics of lung sequelae in COVID-19 patients through retrospective studies according to PRISMA guidelines. Radiological and pulmonary function test (PFT) data were collected and analyzed using one-group meta-analysis in a random-effects model.
Results: Our search identified 9 eligible retrospective studies with follow-up period up to 3 months. A total of 581 discharged patients were evaluated by chest CT scans or PFT. The frequency of residual CT abnormalities after hospital discharge was 61.5% ([95% confidential interval (CI)]: [41.3-81.7], I2=96.0%, 243/421 patients). Pulmonary fibrosis and ground glass opacity was found in 42.7% ([95% CI]: [10.4-74.9], I2=96.31%, 56/166 patients) and 42.4% ([95% CI]: [33.3-51.5], I2=43.0%, 107/250 patients) of patients, respectively. The frequency of abnormal pulmonary function test was 39.2% ([95% CI]: [19.8-58.6], I2=79.4%, 48/123 patients) and impaired diffusion capacity was most frequently observed in 32.8% ([95% CI]: [18.2-47.4], I2=86.2%, 93/272 patients) of patients. Restrictive pattern and obstructive pattern were observed in 10.5% ([95% CI]: [6.9-14.0], I2=0%, 31/290 patients) and 4.8% ([95% CI]: [0.9-8.6], I2=45.8%, 14/240 patients), respectively.
Conclusions: This systematic review analyzed the frequency of chest CT and PFT abnormalities after hospital discharge. 61.5% and 39.2% of patients had abnormal chest CT and PFT results within a period of 3 months after hospital discharge. The most frequent PFT abnormality was impaired diffusion capacity which is potentially suggestive of residual impact of microthromboembolism in lung vasculature due to hypercoagulability. Further studies with longer follow-up term are warranted to elucidate long term consequences of COVID-19 disease.
