Detection of asymptomatic SARS-CoV-2 infections among healthcare workers: results from a large-scale screening program based on rapid serological testing

  1. Francesca Maria Carozzi
  2. Maria Grazia Cusi
  3. Mauro Pistello
  4. Luisa Galli
  5. Alessandro Bartoloni
  6. Gabriele Anichini
  7. Chiara Azzari
  8. Michele Emdin
  9. Claudia Gandolfo
  10. Fabrizio Maggi
  11. Elisabetta Mantengoli
  12. Maria Moriondo
  13. Giovanna Moscato
  14. Irene Paganini
  15. Claudio Passino
  16. Francesco Profili
  17. Fabio Voller
  18. Marco Zappa
  19. Filippo Quattrone
  20. Gian Maria Rossolini
  21. Paolo Francesconi
  22. SARS-CoV-2 serosurvey Tuscan working group

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Abstract

Objective

To evaluate the performance of two available rapid immunological tests for identification of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) antibodies and their subsequent application to a regional screening of health care workers (HCW) in Tuscany (Italy).

Design

measures of accuracy and HCW serological surveillance

Setting

6 major health facilities in Tuscany, Italy.

Participants

17,098 HCW of the Tuscany Region. Measures of accuracy were estimated to assess sensitivity in 176 hospitalized Covid-19 clinical subjects at least 14 days after a diagnostic PCR-positive assay result. Specificity was assessed in 295 sera biobanked in the pre-Covid-19 era in winter or summer 2013-14

Main outcome measures

Sensitivity and specificity, and 95% confidence intervals, were measured using two serological tests, named T-1 and T-2. Positive and Negative predictive values were estimated at different levels of prevalence. HCW of the health centers were tested using the serological tests, with a follow-up nasopharyngeal PCR-test swab in positive tested cases.

Results

Sensitivity was estimated as 99% (95%CI: 95%-100%) and 97% (95% CI: 90%-100%), whereas specificity was the 95% and 92%, for Test T-1 and T-2 respectively. In the historical samples IgM cross-reactions were detected in sera collected during the winter period, probably linked to other human coronaviruses. Out of the 17,098 tested, 3.1% have shown the presence of SARS-CoV-2 IgG antibodies, among them 6.8% were positive at PCR follow-up test on nasopharyngeal swabs.

Conclusion

Based on the low prevalence estimate observed in this survey, the use of serological test as a stand-alone test is not justified to assess the individual immunity status. Serological tests showed good performance and might be useful in an integrated surveillance, for identification of infected subjects and their contacts as required by the policy of contact tracing , with the aim to reduce the risk of dissemination, especially in health service facilities.

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  1. ScreenIT

    SciScore for 10.1101/2020.07.30.20149567: (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 variableThe 295 sera were collected from 145 women and 150 men aged 50-70, equally distributed among gender; among the 295 sera, 200 (100 from men and 100 from women) were collected during winter months (from November to February) and 95 (50 from men and 45 from women) during summer months (July and August).

    Table 2: Resources

    Antibodies
    SentencesResources
    In Tuscany Region, according with the ordinance of the Health Care Department, rapid serological testing for anti-SARS-CoV-2 IgG and IgM antibodies was offered to HCWs during April 2020.
    IgM
    suggested: None
    Rapid serological tests (RST) for anti-SARS-CoV-2 IgG and IgM: Two rapid serological tests (RST) (Screen Test Covid-19 2019-nCOV IgG/IgM by Screen Italia S.r.l and COVID-19 IgG/IgM rapid test cassette by Zhejiang Orient Gene Biotech Co., Ltd) for the detection of anti-SARS-CoV-2 antibodies were used in the present study for large-scale screening and evaluated to assess sensitivity and specificity.
    anti-SARS-CoV-2 IgG
    suggested: None
    COVID-19 IgG/IgM
    suggested: None
    Sensitivity and Specificity Evaluation: Sensitivity of the RST in detecting anti-SARS-CoV-2 antibodies was evaluated considering sera from virologically-confirmed COVID-19 symptomatic patients at advanced stages of the disease as true positives.
    anti-SARS-CoV-2
    suggested: None
    Software and Algorithms
    SentencesResources
    The present report describes the results of the survey carried out on HCWs of the four Tuscan University Hospitals (AOUS in Siena, AOUC in Florence, AOUP in Pisa, and AOUM, the Meyer Children’s University Hospital, in Florence) and of two additional healthcare Institutions, the Institute for prevention, research and oncological network (ISPRO) in Florence and the Fondazione Toscana Gabriele Monasterio (FTGM) in Pisa and Massa.
    Pisa
    suggested: (PISA, RRID:SCR_015749)

    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: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    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 10.1101/2020.07.30.20149567 on medRxiv