Follow-up study of the pulmonary function and related physiological characteristics of COVID-19 survivors three months after recovery

Abstract

Background: The long-term pulmonary function and related physiological characteristics of COVID-19 survivors have not been studied in depth, thus many aspects are not understood.

Methods: COVID-19 survivors were recruited for high resolution computed tomography (HRCT) of the thorax, lung function and serum levels of SARS-CoV-2 IgG antibody tests 3 months after discharge. The relationship between the clinical characteristics and the pulmonary function or CT scores were investigated.

Findings: Fifty-five recovered patients participated in this study. SARS-CoV-2 infection related symptoms were detected in 35 of them and different degrees of radiological abnormalities were detected in 39 patients. Urea nitrogen concentration at admission was associated with the presence of CT abnormalities (P = 0.046, OR 7.149, 95% CI 1.038 to 49.216). Lung function abnormalities were detected in 14 patients and the measurement of D-dimer levels at admission may be useful for prediction of impaired diffusion defect (P = 0.031, OR 1.066, 95% CI 1.006 to 1.129). Of all the subjects, 47 of 55 patients tested positive for SARS-CoV-2 IgG in serum, among which the generation of Immunoglobulin G (IgG) antibody in female patients was stronger than male patients in infection rehabilitation phase.

Interpretation: Radiological and physiological abnormalities were still found in a considerable proportion of COVID-19 survivors without critical cases 3 months after discharge. Higher level of D-dimer on admission could effectively predict impaired DLCO after 3 months discharge. It is necessary to follow up the COVID-19 patients to appropriately manage any persistent or emerging long-term sequelae.

Funding: Key Scientific Research Projects of Henan Higher Education Institutions.

Keywords: Covid-19; Follow-up study; Pulmonary function; Recovered patients; Serum marker.

Fig. 1

Enrolment of patients and follow-up at 3 months after hospital discharge. COVID-19: Coronavirus Disease 2019.

Fig. 2

Follow-up thin-section CT imaging of 63-year-old man with confirmed COVID-19 pneumonia with dry cough. (A) First thin-section chest CT in hospital on February 2, 2020 (7 days after symptoms onset). CT imaging shows GGO associated with smooth interlobular and intralobular septal thickeing (crazy paving). (B) Crazy paving with some consolidations were observed over 7 days. (C) On March 4, 2020, scans showed that the previous lesion was absorbed and parenchymal bands with residual GGO were observed. (D) On May 2, 2020, intenstitial thickeing and residual GGO were observed. CXR: chest radiography.

Fig. 3

Spearman's correlation analysis for CXR score 3 month after discharge with pulmonary function: DLCO% predicted (A), TLC% predicted (B), FEV₁% predicted (C), and FVC% predicted (D).

Fig. 4

Comparison of SARS-CoV-2 IgG antibody concentration between male and female patients in recovering status (A). Spearman's correlation analysis for CXR peak score with SARS-CoV-2 IgG antibody in recovered COVID-19 patients (B).