Comparative Evaluation of Three Serologic Assays for the Identification of SARS-CoV-2 Antibodies

  1. Keenan Hogan
  2. Dave Klippel
  3. Fred Plapp
  4. Rachael Liesman

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Abstract

Serologic assays for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies continue to be developed and approved rapidly with limited external validation. Accurate diagnostics are an essential component of pandemic management and public health. Residual serum samples (N=113) from patients who were evaluated for SARS-CoV-2 infection status by polymerase chain reaction (PCR) were retrospectively tested in parallel across three automated SARS-CoV-2 serologic assays: Liaison SARS-CoV-2 S1/S2 IgG, Elecsys anti-SARS-CoV-2 total antibody, and Access SARS-CoV-2 IgG. Testing of 51 PCR-positive and 62 PCR-negative patients demonstrated qualitative inter-test agreement of 96% overall, 100% in PCR-negative patients, 88% in early positive samples (0-13 days post positive PCR), and 100% in convalescent samples (14+ days post positive PCR). Calculated kappa values for paired inter-test agreement ranged 0.93-0.96. Compared to PCR, overall percent positive agreement ranged from 82-86% (100% for convalescent samples) and percent negative agreement was 100% for each assay. This study demonstrates high diagnostic accuracy and inter-test agreement for three automated SARS-CoV-2 serologic assays. External validation of serologic assays is critical to ensure diagnostic accuracy and appropriate utilization of critical resources.

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  1. Version published to 10.1093/ajcp/aqab189.030
  2. ScreenIT

    SciScore for 10.1101/2020.08.04.20167643: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIRB: This study was approved by the University of Kansas Medical Center institutional review board prior to testing.
    RandomizationSamples were collected for two groups: (1) serum samples from patients who tested positive for SARS-CoV-2 by an RT-PCR assay, and (2) serum samples from randomly selected patients who had tested negative for SARS-CoV-2 by an RT-PCR assay within 48 hours prior to collection.
    BlindingClinical Laboratory Scientists were not specifically blinded to the clinical status or PCR results of the patients.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Patient serum is combined with magnetic particles coated with biotinylated recombinant S1/S2 antigen, which binds to SARS-CoV-2 antibody, if present.
    SARS-CoV-2
    suggested: None
    Following incubation, isoluminol labeled mouse anti-human IgG are added, which will bind to the SARS-CoV-2 antibody.
    anti-human IgG
    suggested: None
    Monoclonal anti-human IgG alkaline phosphatase conjugate is added to bind IgG antibodies captured on the particles.
    bind IgG
    suggested: None
    Software and Algorithms
    SentencesResources
    Briefly, nasopharyngeal swabs collected in either UTM or PBS were tested with the Abbott RealTime SARS-CoV-2 assay (Abbott Diagnostics Inc, Scarborough, ME), performed on the Abbott m2000 instrument, or the Simplex COVID-19 Direct assay (DiaSorin Molecular LLC, Cypress CA), following manufacturer’s instructions.
    Abbott
    suggested: (Abbott, RRID:SCR_010477)
    Statistical analysis was performed using GraphPad Prism 8 statistics software (San Diego, USA).
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)

    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:
    Overall, evidence is limited and laboratories offering serology testing for SARS-CoV-2 must make these limitations clear. For patients with a complicated medical history or atypical presentation, antibody testing may provide important diagnostic information. It has been reported that overall sensitivity for serology is greater than nucleic acid testing for SARS-CoV-2 starting day 8 after symptom onset and combined serology and RT-PCR testing provides significantly improved sensitivity compared to RT-PCR alone early in the disease course [17,20]. 4.2 Limitations: This study has several limitations. The testing of a relatively small number of retrospective convenience samples is at risk for confirmation basis and underpowered calculations. Specifically, our cohort of inpatients likely includes a greater average patient acuity, which would tend to inflate sensitivity. This may also increase the number of false positive results, which was not identified. In the absence of thorough chart review for the PCR-negative cohort, the presence of confounding factors contributing to an artificially high true negative rate cannot be excluded but is considered unlikely. By combining specimens from sequential days and using the farthest date, we likely reduced the reportable sensitivity. Longitudinal samples from individual patients were not tested to track seroconversion. The samples were not tested to ascertain the presence of potential cross-reactive viruses. One of the strengths of this s...

    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 10.1101/2020.08.04.20167643v1 on medRxiv