Development and multicenter performance evaluation of fully automated SARS-CoV-2 IgM and IgG immunoassays

  1. Chungen Qian
  2. Mi Zhou
  3. Fangming Cheng
  4. Xiaotao Lin
  5. Yijun Gong
  6. Xiaobing Xie
  7. Ping Li
  8. Zhiyong Li
  9. Pingan Zhang
  10. Zejin Liu
  11. Fang Hu
  12. Yun Wang
  13. Quan Li
  14. Yan Zhu
  15. Guikai Duan
  16. Yinting Xing
  17. Huanyu Song
  18. Wenfang Xu
  19. Bi-Feng Liu
  20. Fuzhen Xia

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Abstract

Objectives

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread globally. The laboratory diagnosis of SARS-CoV-2 infection has relied on nucleic acid testing; however, it has some limitations, such as low throughput and high rates of false negatives. Tests of higher sensitivity are needed to effectively identify infected patients.

Methods

This study has developed fully automated chemiluminescent immunoassays to determine IgM and IgG antibodies to SARS-CoV-2 in human serum. The assay performance has been evaluated at 10 hospitals. Clinical specificity was evaluated by measuring 972 hospitalized patients and 586 donors of a normal population. Clinical sensitivity was assessed on 513 confirmed cases of SARS-CoV-2 by RT-PCR.

Results

The assays demonstrated satisfied assay precision with coefficient of variation of less than 4.45%. Inactivation of specimen did not affect assay measurement. SARS-CoV-2 IgM showed clinical specificity of 97.33 and 99.49% for hospitalized patients and the normal population respectively, and SARS-CoV-2 IgG showed clinical specificity of 97.43 and 99.15% respectively. SARS-CoV-2 IgM showed clinical sensitivity of 82.54, 92.93, and 84.62% before 7 days, 7–14 days, and after 14 days respectively, since onset of symptoms, and SARS-CoV-2 IgG showed clinical sensitivity of 80.95, 97.98, and 99.15% respectively at the same time points above.

Conclusions

We have developed fully automated immunoassays for detecting SARS-CoV-2 IgM and IgG antibodies in human serum. The assays demonstrated high clinical specificity and sensitivity, and add great value to nucleic acid testing in fighting against the global pandemic of the SARS-CoV-2 infection.

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  1. Version published to 10.1515/cclm-2020-0548
  2. ScreenIT

    SciScore for 10.1101/2020.04.16.20067231: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Mouse monoclonal anti-human IgM or IgG (purchased from Fapon Biotech) were conjugated with NSP-DMAE-NHS (purchased from Maxchemtech), and the conjugated antibodies were then purified by gel filtration on a Sephadex G-50 column.
    anti-human IgM
    suggested: (Meridian Life Science Cat# C5G50-296, RRID:AB_817062)
    NSP-DMAE-NHS
    suggested: None
    PRINCIPLE OF THE ASSAY: The SARS-CoV-2 IgM and IgG assays are two-step immunoassays for the qualitative detection of SARS-CoV-2 IgM and IgG antibodies in human serum and plasma, using direct chemiluminometric microparticle technology (10, 11).
    IgG
    suggested: None
    A direct relationship exists between the amount of SARS-CoV-2 IgM or IgG antibodies in the sample and the RLUs detected by the optical system of the immune analyzer.
    SARS-CoV-2 IgM
    suggested: None
    IgG antibodies in the sample and the RLUs detected by the optical system of the immune analyzer.
    suggested: None

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    It is critical for an alternative testing method to be developed to compensate for this limitation of nucleic acid testing. Antibodies are proteins produced by the immune system after being stimulated by viral pathogens, and usually very little viral antigen can stimulate the body to produce enough antibodies that can be detected by sensitive immunoassays. The generation and detection of antibodies to viruses are usually not affected by the status of virus in the body, even during the dormant phase of viruses. In addition, as peripheral blood is used for antibody detection, sample collection is easily controlled than nasopharyngeal swabs and is not influenced by a sample collector’s operational deviation, ensuring a better repeatability of the test results. It also does not impose higher biological risk for sample collectors. This study evaluated SARS-CoV-2 IgM and IgG immunoassays for their clinical specificity using serum from 586 healthy individuals, and the specificity of both the IgM and IgG assays exceeded 99%. When evaluated with 972 serum samples from hospitalized patients diagnosed with diseases other than COVID-19, the two assays demonstrated clinical specificity of greater than 97%. Due to interference on immunoassays, the specificity based on inpatient samples is usually lower than that based on healthy population, especially the immunoassays for markers of infectious diseases. Many factors could be involved in affecting the specificity of SARS-CoV-2 IgM and IgG i...

    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.

  3. Version published to 10.1101/2020.04.16.20067231 on medRxiv