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Dynamic Monitoring of Seroconversion using a Multianalyte Immunobead Assay for Covid-19
Published on: February 16, 2022
A longitudinal follow-up of COVID-19 patients in the convalescent phase showed recovery in radiological results, the
Ziqi Wang1, Li Yang1, Yi Chen2
1Department of Respiratory and Critical Care Medicine, Zhengzhou University People's Hospital, Henan Provincial People's Hospital, Zhengzhou, China.
Insights
Many COVID-19 survivors experience persistent lung abnormalities and lymphopenia for weeks after discharge. Antibody levels, particularly S-RBD IgG, also decline, impacting long-term immunity and vaccine strategies.
Area of Science:
- Immunology
- Infectious Diseases
- Radiology
Background:
- High global prevalence of COVID-19 necessitates understanding long-term health consequences for convalescent patients.
- Public health policy requires data on post-discharge health status and recovery trajectories.
Purpose of the Study:
- To investigate the persistent radiological and immunological sequelae of COVID-19.
- To evaluate the duration of lymphopenia and antibody levels in recovered patients.
- To inform public health policy and vaccine development strategies.
Main Methods:
- Longitudinal follow-up of 25 COVID-19 patients 8 weeks post-discharge, with 15 attending a second 8-week follow-up.
- Chest CT scans and SARS-CoV-2 RT-PCR performed at the first follow-up.
- Evaluation of lymphocyte subpopulations (via flow cytometry) and SARS-CoV-2 specific IgG antibodies (S-RBD and NP via ELISA) in collected blood samples.
Main Results:
- At 8 weeks post-discharge, 40% of patients had radiological abnormalities and 40% exhibited lymphopenia.
- Lymphopenia persisted up to 16 weeks in 46.7% of patients, primarily due to decreased CD4+ T cells.
- All patients had positive S-RBD and NP IgG antibodies initially, but levels declined over time, with S-RBD IgG decreasing more significantly; 26.7% converted to negative for S-RBD IgG.
Conclusions:
- A significant proportion of COVID-19 patients experience persistent chest CT abnormalities and lymphopenia for up to 16 weeks post-discharge.
- Declining IgG antibody levels, especially against S-RBD, suggest potential waning immunity.
- Findings underscore the need for long-term patient management strategies and inform vaccine efficacy considerations.
Background:
Given the high prevalence of coronavirus disease 2019 (COVID-19) globally, and the increased number of patients being discharged, it is necessary to understand the health consequences of COVID-19 to formulate and manage public policy concerning convalescent patients.
Methods:
A longitudinal follow-up investigation of 25 patients from a tertiary hospital in Henan provincial was conducted 8 weeks after discharge. Of these patients, 15 attended a second follow-up appointment 8 weeks after that. A throat swab reverse transcription-polymerase chain reaction (RT-PCR) analysis for SARS-CoV-2 and chest computerized tomography (CT) scans were implemented at the first follow-up appointment, and a total of 40 blood samples (25 from the first and 15 from the second follow-up appointment) were collected. Patients' levels of Immunoglobulin G (IgG) antibody against S-Receptor binding domain (S-RBD) and Nucleocapsid Protein (NP) of SARS-CoV-2 and the subpopulation of lymphocytes were evaluated using an enzyme-linked immunoassay (ELISA) test and flow cytometry, respectively.
Results:
At the first follow-up appointment, 10 of the 25 patients (40.0%) showed complete radiological resolution. Of these patients, 80.0% were classified as moderate, and 80.0% were younger (those whose age was ≤ the median age of all the patients). The predominant patterns of abnormalities included an irregular line (12/25, 48.0%), ground-glass opacity (GGO) (44.0%), and multiple GGOs (28.0%). At the first follow-up appointment, 40.0% (10/25) of patients still had lymphopenia. Of the 15 patients who were followed-up with twice, the ratio of lymphopenia was 80% (12/15), 60.0% (9/15), and 46.7% (7/15) at 0, 8, and 16 weeks after discharge, respectively. This was mainly due to a decrease in the cluster of differentiation (CD) 4+ T lymphocyte, which was observed in 60% (9/15), 60% (9/15), and 46.7% (7/15) of total patients at 0, 8, and 16 weeks after discharge, respectively. All of the patients were S-RBD and NP IgG antibody positive at the first follow-up appointment. 40.0% (6/15) and 66.7% (10/15) of patients showed a decrease over 50.0% in the level of NP and S-RBD IgG antibodies, respectively, at the second follow-up appointment. The NP and S-RBD IgG antibodies' levels declined to 44.6% (P=0.044) and 28.1% (P=0.18), respectively. 0 and 26.7% (4/15) of patients turned from NP and S-RBD IgG antibody positive to negative, respectively.
Conclusions:
About half of the patients still showed at least 1 abnormality in chest CT scans 8 weeks after discharge and lymphopenia 16 weeks after discharge. The level of the IgG antibody had declined by the follow-up appointment. Notably, the S-RBD IgG antibody declined more dramatically than that of NP. These results may have implications in the making of policies related to disease prevention, the long-term management of discharged patients, and vaccines' development.
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