SARS-Coronavirus-2 nucleocapsid protein measured in blood using a Simoa ultra-sensitive immunoassay differentiates COVID-19 infection with high clinical sensitivity

  1. Dandan Shan
  2. Joseph M Johnson
  3. Syrena C. Fernandes
  4. Muriel Mendes
  5. Hannah Suib
  6. Marcella Holdridge
  7. Elaine M Burke
  8. Katie Beauregard
  9. Ying Zhang
  10. Megan Cleary
  11. Samantha Xu
  12. Xiao Yao
  13. Purvish Patel
  14. Tatiana Plavina
  15. David Wilson
  16. Lei Chang
  17. Kim M Kaiser
  18. Jacob Natterman
  19. Susanne V Schmidt
  20. Eicke Latz
  21. Kevin Hrusovsky
  22. Dawn Mattoon
  23. Andrew J. Ball

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Abstract

The COVID-19 pandemic continues to have an unprecedented impact on societies and economies worldwide. Despite rapid advances in diagnostic test development and scale-up, there remains an ongoing need for SARS-CoV-2 tests which are highly sensitive, specific, minimally invasive, cost-effective and scalable for broad testing and surveillance. Here we report development of a highly sensitive single molecule array (Simoa) immunoassay on the automated HD-X platform for the detection of SARS-CoV-2 Nucleocapsid protein (N-protein) in venous and capillary blood (fingerstick). In pre-pandemic and clinical sample sets, the assay has 100% specificity and 97.4% sensitivity for serum / plasma samples. The limit of detection (LoD) estimated by titration of inactivated SARS-CoV-2 virus is 0.2 pg/ml, corresponding to 0.05 Median Tissue Culture Infectious Dose (TCID50) per ml, > 2000 times more sensitive than current EUA approved antigen tests. No cross-reactivity to other common respiratory viruses, including hCoV229E, hCoVOC43, hCoVNL63, Influenza A or Influenza B, was observed. We detected elevated N-protein concentrations in symptomatic, asymptomatic, and pre-symptomatic PCR+ individuals using capillary blood from a finger-stick collection device. The Simoa SARS-CoV-2 N-protein assay has the potential to detect COVID-19 infection via antigen in blood with performance characteristics similar to or better than molecular tests, while also enabling at home and point of care sample collection.

One Sentence Summary

SARS-CoV-2 nucleocapsid protein (N-protein) measured in serum, plasma, and dried blood spots (DBS) via ultrasensitive immunoassay can be used to differentiate PCR+ from PCR- patients, even if asymptomatic.

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  1. Version published to 10.1101/2020.08.14.20175356v2 on medRxiv
  2. ScreenIT

    SciScore for 10.1101/2020.08.14.20175356: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIRB: The study was approved by the Institutional Review board of the University Hospital Bonn (134/20).
    Consent: Patients were included after providing written informed consent.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    No key resources detected.

    Results from OddPub: Thank you for sharing your data.

    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

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  3. Version published to 10.1101/2020.08.14.20175356v1 on medRxiv