Antibody seroprevalence and rate of asymptomatic infections with SARS-CoV-2 in Austrian hospital personnel

  1. Iris Leister
  2. Elisabeth Ponocny-Seliger
  3. Herwig Kollaritsch
  4. Peter Dungel
  5. Barbara Holzer
  6. Johannes Grillari
  7. Heinz Redl
  8. Ivo Ponocny
  9. Claudia Wilfing
  10. Ludwig Aigner
  11. Markus Exner
  12. Michaela Stainer
  13. Matthias Hackl
  14. Thomas Hausner
  15. Rainer Mittermayr
  16. Wolfgang Schaden

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Abstract

Background

The aims of this study are to determine (i) SARS-CoV-2 antibody positive employees in Austrian trauma hospitals and rehabilitation facilities, (ii) number of active virus carriers (symptomatic and asymptomatic) during the study, (iii) antibody decline in seropositive subjects over a period of around 6 months, (iv) the usefulness of rapid antibody tests for outpatient screening.

Method

A total of 3301 employees in 11 Austrian trauma hospitals and rehabilitation facilities of the Austrian Social Insurance for Occupational Risks (AUVA) participated in this open uncontrolled prospective cohort study.

Rapid lateral flow tests, detecting a combination of IgM and IgM against SARS-CoV-2), two different types of CLIA (Diasorin, Roche), RT-PCR tests and serum neutralization tests (SNTs) were performed. The tests were conducted twice, with an interval of 42.4 ± 7.7 (Min = 30, Max = 64) days. Positive participants were re-tested with CLIA/SNT at a third time point after 188.0 ± 12.8 days.

Results

Only 27 out of 3301 participants (0.82%) had a positive antibody test at any time point during the study confirmed via neutralization test. Among positively tested participants in either test, 50.4% did not report any symptoms consistent with common manifestations of COVID-19 during the study period or within the preceding 6 weeks. In the group who tested positive during or prior to study inclusion the most common symptoms of an acute viral illness were rhinitis (21.9%), and loss of taste and olfactory sense (21.9%).

Based on the neutralization test as the true condition, the rapid antibody test performed better on serum than whole blood as 84.6% instead of 65.4% could be detected correctly. Concerning both CLIA tests overall the Roche test detected 24 (sensitivity = 88.9%) and the Diasorin test 22 positive participants (sensitivity = 81.5%).

In participants with a positive SNT result, a significant drop in neutralizing antibody titre from 31.8 ± 22.9 (Md = 32.0) at T1 to 26.1 ± 17.6 (Md = 21.3) at T2 to 21.4 ± 13.4 (Md = 16.0) at T3 (χ 2  = 23.848, df = 2, p < 0.001) was observed (χ 2  = 23.848, df = 2, p < 0.001)—with an average time of 42.4 ± 7.7 days between T1 and T2 and 146.9 ± 13.8 days between T2 and T3.

Conclusions

During the study period (May 11th–August 3rd) only 0.82% were tested positive for antibodies in our study cohort. The antibody concentration decreases significantly over time with 14.8% (4 out of 27) losing detectable antibodies.

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  1. Version published to 10.1186/s12879-021-06586-7
  2. ScreenIT

    SciScore for 10.1101/2021.02.01.21250898: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementConsent: Written informed consent has been obtained from all study participants.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variableThe mean(SD) age in the cohort was 43.8 (11.9) years, 2246 (68%) are female, 1049 (31.8%) are male, and 6 (0.2%) refused to disclose their gender.

    Table 2: Resources

    Antibodies
    SentencesResources
    A rapid antibody test (chip based) for SARS-CoV-2 specific IgG and IgM antibodies, and an RT-PCR test based on oropharyngeal swab samples, as well as the ELISA / PRNT tests (if indicated) were offered to all employees in Austrian trauma hospitals and rehabilitation facilities.
    SARS-CoV-2 specific IgG
    suggested: None
    Laboratory-based ELISA (Roche and Diasorin): SARS-CoV-2 specific antibodies were measured from serum samples with two assays: (i) a qualitative eCLIA assay targeting pan-immunoglobulin (IgM, IgA, IgG) antibodies against the nucleoprotein (N-Ag
    pan-immunoglobulin (IgM, IgA, IgG
    suggested: None
    Results of the PCR and rapid antibody test (IgG and IgM) were included in the eCRF at both time points together with all questionnaire data.
    IgM
    suggested: None
    Software and Algorithms
    SentencesResources
    Neutralization test: Statistical analysis: Statistical analysis was performed using SPSS statistical software (version 26, SPSS Inc., Chicago, Illinois, USA).
    SPSS
    suggested: (SPSS, RRID:SCR_002865)
    Figures were compiled with Biorender.com, draw.io, and Microsoft Excel (Microsoft Corp.,
    Microsoft Excel
    suggested: (Microsoft Excel, RRID:SCR_016137)

    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:
    Limitations: Antibody seroprevalence may be underestimated if participants had not yet produced a sufficient antibody response at the time of sample collection, or if antibody titers had already declined since the infection. We tried to reduce this bias by conducting the PCR and LFA tests twice with approximately six weeks in between testing (between T1 and T2) and an additional serum sample collection for ELISA / PRNT after another three months (between T2 and T3).

    Results from TrialIdentifier: We found the following clinical trial numbers in your paper:

    IdentifierStatusTitle
    NCT04354779CompletedAntibody Seroprevalence and Rate of Asymptomatic Infections …

    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 10.1101/2021.02.01.21250898v1 on medRxiv