Radiological and Functional Lung Sequelae of COVID-19

A Systematic Review and Meta-Analysis

Matsuo So; Hiroki Kabata; Koichi Fukunaga; Hisato Takagi; Toshiki Kuno


BMC Pulm Med. 2021;21(97) 

In This Article

Abstract and Introduction


Background: The coronavirus disease 2019 (COVID-19) causes a wide spectrum of lung manifestations ranging from mild asymptomatic disease to severe respiratory failure. We aimed to clarify the characteristics of radiological and functional lung sequelae of COVID-19 patients described in follow-up period.

Method: PubMed and EMBASE were searched on January 20th, 2021 to investigate characteristics of lung sequelae in COVID-19 patients. Chest computed tomography (CT) and pulmonary function test (PFT) data were collected and analyzed using one-group meta-analysis.

Results: Our search identified 15 eligible studies with follow-up period in a range of 1–6 months. A total of 3066 discharged patients were included in these studies. Among them, 1232 and 1359 patients were evaluated by chest CT and PFT, respectively. The approximate follow-up timing on average was 90 days after either symptom onset or hospital discharge. The frequency of residual CT abnormalities after hospital discharge was 55.7% (95% confidential interval (CI) 41.2–70.1, I 2 = 96.2%). The most frequent chest CT abnormality was ground glass opacity in 44.1% (95% CI 30.5–57.8, I 2 = 96.2%), followed by parenchymal band or fibrous stripe in 33.9% (95% CI 18.4–49.4, I 2 = 95.0%). The frequency of abnormal pulmonary function test was 44.3% (95% CI 32.2–56.4, I 2 = 82.1%), and impaired diffusion capacity was the most frequently observed finding in 34.8% (95% CI 25.8–43.8, I 2 = 91.5%). Restrictive and obstructive patterns were observed in 16.4% (95% CI 8.9–23.9, I 2 = 89.8%) and 7.7% (95% CI 4.2–11.2, I 2 = 62.0%), respectively.

Conclusions: This systematic review suggested that about half of the patients with COVID-19 still had residual abnormalities on chest CT and PFT at about 3 months. Further studies with longer follow-up term are warranted.


Coronavirus disease 2019 (COVID-19) is caused by a novel coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2),[1] which was identified to be the cause of pneumonia cases originated in Wuhan, a city in the providence of Hubei, China. COVID-19 infection rapidly spread to entire world, leading WHO to declare pandemic on March 11, 2020. As of February 24, 2021, WHO reported 111,593,583 cases and 2,475,020 deaths.[2]

Although COVID-19 is known to cause multiple organ damages, pneumonia is the most frequent manifestation of infection ranging from mild asymptomatic cases to critical respiratory failure requiring ventilatory support.[3] Initial symptoms of COVID-19, lung complications, radiological features, and the management have been extensively reported. Importantly, persistent symptoms such as fatigue, dyspnea, joint pain, and chest pain in patients discharged from hospital at 60 days after symptom onset were reported.[4] During the worldwide outbreak of severe acute respiratory syndrome (SARS) in 2003, persistent residual lung fibrosis was reported in 62% of patients in chest computed tomography obtained on average 36.5 days after hospital admission[5] and can be still present in 7 years after symptom presentation.[6] In addition, impairment in diffusion capacity in SARS survivors has been reported in 25.5% of patients on average 40.5 days after hospital discharge.[7,8] Another study also showed forced vital capacity < 80% predicted in 4.1% of patients and impaired diffusion capacity in 23.7% of patients at 1 year after disease onset.[9,10] Similarly, studies of Middle East respiratory syndrome (MERS) survivors revealed that 33% of patients had chest radiograph abnormalities at 80 days after discharge[11] and 37% of patients had impaired diffusion capacity at 1 year after disease onset.[12] These radiological and functional lung sequelae can detrimentally affect survivors' quality of life. Reports of lung sequelae regarding chest CT findings and PFT observed in patients with clinical recovery from COVID-19 has been increasing recently. Herein, we conducted this systematic review to clarify the characteristics of chest CT findings and PFT results in follow-up period after COVID-19.