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Updated: Nov 25, 2025
Dynamic Monitoring of Seroconversion using a Multianalyte Immunobead Assay for Covid-19
Published on: February 16, 2022
[Preliminary study of the antibody level in confirmed patients with COVID-19 after discharge]
1Medical Laboratory,Loudi Center for Diseases Prevention and Control of Hunan, Loudi 417000, China.
Insights
This study analyzed antibody levels in 72 COVID-19 patients post-discharge. IgM antibodies decreased rapidly, while IgG remained high before declining, with a 6.94% re-infection rate observed, highlighting the need for antibody monitoring.
Area of Science:
- Immunology
- Infectious Diseases
- Virology
Background:
- Understanding the dynamics of antibody response following 2019-novel coronavirus (COVID-19) infection is crucial for managing patient recovery and preventing reinfection.
- Previous studies have indicated varying antibody levels, but detailed analysis of IgM and IgG over time post-discharge is needed.
Purpose of the Study:
- To analyze the antibody levels and dynamic changes in patients infected with 2019-novel coronavirus (COVID-19) after hospital discharge.
- To investigate the correlation between antibody levels, patient demographics, and the occurrence of potential reinfection.
Main Methods:
- A cohort of 72 discharged COVID-19 patients had their serum samples collected at various time points post-discharge.
- Antibody levels (IgM and IgG) were detected using the chemiluminescence method.
- Statistical analyses, including ANOVA and chi-squared tests, were performed using SPSS 25.0 to compare demographic data and antibody concentrations.
Main Results:
- The overall positive rate for IgM or IgG antibodies was 97.22%. IgM antibody levels decreased significantly over time after discharge, becoming negative by the third week.
- IgG antibody concentrations remained high initially and showed a slower decline, persisting longer than IgM.
- A notable 6.94% of patients experienced potential 're-infection' within 1-3 weeks post-discharge, indicating a need for continued monitoring.
Conclusions:
- Antibody levels post-COVID-19 discharge exhibit significant individual variation but follow predictable patterns, with IgM declining faster than IgG.
- The observed rate of 're-infection' suggests that antibody levels may not confer complete long-term immunity.
- Continuous antibody monitoring during hospitalization and after discharge is recommended to mitigate reinfection risks.
Abstract:
Objective: To analyze the antibody levels and dynamic changes in patients infected with 2019-novel coronavirus(2019-nCoV). Methods: The average age of 72 corona virus disease 2019 (COVID-19) patients was (45.53±16.74)years(median age:47 year), including (44.88±17.09) years(median age:46 year) for 38 males and (46.32±16.52)years (median age:46 year) for 34 females in Loudi City, Hunan Province. There is no significant difference in genders between the severe and mild groups (χ²=0.916, P>0.05). There is a significant difference in the age between the severe and mild groups (F=3.315, P<0.05). The blood samples of 72 discharged patients were collected and the consistence of IgM and IgG antibodies were detected by chemiluminescence method. SPSS25.0 was used for gender, age, case type and antibody analysis of variance, χ2 test and other analysis. Results: The average time of the serum samples collection of 72 patients was (34.89±9.02)days (median time: 34 days) from onset of COVID-19, and (14.53±8.35) days (median time: 14 days) from discharge. The positive rate of IgM or IgG was 97.22% (70/72), and the positive rate of IgM and IgG was 48.61% (35/72) and 97.22% (70/72) respectively. Serum COVID-19 antibodies were detected in 72 patients from 1st to 40th days after discharge. The average concentration of IgM in 1-7 days, 8-14 days, 15-21 days, 22-28 days, above 29 days were 21.91(7.07-52.84)AU/ml, 14.16(6.19-32.88)AU/ml, 11.36(6.65-42.15)AU/ml, 8.15(3.66-30.12)AU/ml, 2.98(0.46-6.37)AU/ml. There was no significant difference in the time of IgM antibody concentration (H= 8.439, P>0.05). The average concentrations of IgG in 1-7 days, 8-14 days, 15-21 days, 22-28 days, 29 days and above were 169.90 (92.06-190.91) AU/ml, 163.89 (91.19-208.02) AU/ml, 173.31 (95.06-191.28) AU/ml, 122.84 (103.19-188.34) AU/ml, 101.98 (43.75-175.30) AU/ml, respectively, (H=2.232, P>0.05). The IgM becomes negative after the 3rd week of discharge and decreases rapidly with time. The IgG concentration higher than IgM during the same period, and keep at high level without any change, and decrease in the fourth week. Among them, 5 cases developed "re-infection" within 1-3 weeks after discharge, and the rate of "re-infection" was 6.94% (5/72 cases). Conclusions: After the COVID-19 patients are discharged from the hospital, the level of antibodies produced varies greatly among individuals, but the overall changes in antibodies have a certain pattern. It is recommended to strengthen the antibody monitoring during hospitalization and after discharge from the hospital to reduce the "re-infection" rate and potential risk of infection.
