A preliminary study on analytical performance of serological assay for SARS-CoV-2 IgM/IgG and application in clinical practice

  1. Quan Zhou
  2. Danping Zhu
  3. Huacheng Yan
  4. Jingwen Quan
  5. Zhenzhan Kuang
  6. Weiyun Zhang
  7. Ling Huang
  8. Ting Lei
  9. Jiahui Liu
  10. Bin Xiao
  11. Aiwu Luo
  12. Zhaohui Sun
  13. Linhai Li

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Abstract

Objective

To investigate the performance of serological test and dynamics of serum antibody with the progress of SARS-CoV-2 infections.

Methods

A total of 419 patients were enrolled including 19 confirmed cases and 400 patients from fever clinics. Their serial serum samples collected during the hospitalization were menstruated for IgM and IgG against SARS-CoV-2 using gold immunochromatographic assay and chemiluminescence immunoassay. We investigated whether thermal inactivation could affect the results of antibody detection. The dynamics of antibodies with the disease progress and false positive factors for antibody testing were also analyzed.

Results

The positive rate of IgG detection was 91.67% and 83.33% using two CLIA, respectively. However, the IgM positive rate was dramatically declined might due to the lack of blood samples at early stages of the disease. The chemiluminescence immunoassay had a favorable but narrow linear range. Our work showed increased IgG values in serums from virus-negative patients and four negative samples were IgG weak-positive after thermal incubation. Our data showed the specificity of viral N+S proteins was higher than single antigen. Unlike generally thought that IgM appeared earlier than IgG, there is no certain chronological order of IgM and IgG seroconversion in COVID-19 patients. It was difficult to detect antibodies in asymptomatic patients suggesting that their low viral loads were not enough to cause immune response. Analysis of common interferent in three IgG false-positive patients, such as rheumatoid factor, proved that false positives were not caused by these interfering substances and antigenic cross-reaction.

Conclusions

Viral serological test is an effective means for SARS-CoV-2 infect detection using both chemiluminescence immunoassay and gold immunochromatographic assay. Chemiluminescence immunoassay against multi-antigens has obvious advantages but still need improve in reducing false positives.

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  1. ScreenIT

    SciScore for 10.1101/2020.05.05.20092551: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIRB: The study was reviewed approved by the Medical Ethical Committee of General Hospital of Southern Theater Command of PLA. 2.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    The IgM antibody and IgG antibody against SARS-CoV-2 kits (chemiluminescence immunoassay, CLIA) and their testing equipment were purchased from Shenzhen YHLO Biotech Co., Ltd. and Shenzhen Tisenc Medical Devices Co.
    IgM
    suggested: None
    Chemiluminescence immunoassay and colloidal gold immunochromatography test: To quantitatively detect anti-SARS-Cov-2 antibodies in serum, two chemiluminescence immunoassays (CLIA) were applied.
    anti-SARS-Cov-2
    suggested: None
    The antibody qualitative test was also carried out using gold immunochromatographic assay (GICA) purchased from Guangzhou Wondfo company.
    GICA
    suggested: None
    Software and Algorithms
    SentencesResources
    Instruments and reagents: Virus preservation tube was purchased from Shenzhen Biocomma Biological Science and Technology Co., Ltd.
    Biocomma Biological
    suggested: None
    purifier96 Magnetic particle separator was purchase from Genfine Biological Science and Technology (Changzhou) Co., Ltd.
    Genfine Biological
    suggested: None
    Statistical analysis: GraphPad Prism Version 8 software was employed for statistical analysis.
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)

    Results from OddPub: Thank you for sharing your data.

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    The present study has some notable limitations. First, only 19 laboratory confirmed COVID-19 patients were included. It can’t tell whether certain conclusions were exceptional or universal. Second, as a retrospective study, it was difficult to completely match the sampling time and detection time. Therefore, in antibody dynamic monitoring, there was large time spans resulting in incomplete dynamic curves. Third, viral serological detection kits were available late after COVID-19 outbreak, and IgM detection in the acute phase will be partially lost. Finally, due to the limitation of the sample size and serum amount, no systematic analysis has been carried out in comparison of various reagents, and the conclusion may be biased. In conclusion, viral serological testing is an effective means for SARS-CoV-2 infection detection using both chemiluminescence immunoassay and gold immunochromatographic assay.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2020.05.05.20092551 on medRxiv