Rapid Serological Assays and SARS-CoV-2 Real-Time Polymerase Chain Reaction Assays for the Detection of SARS-CoV-2: Comparative Study

  1. Angelo Virgilio Paradiso
  2. Simona De Summa
  3. Daniela Loconsole
  4. Vito Procacci
  5. Anna Sallustio
  6. Francesca Centrone
  7. Nicola Silvestris
  8. Vito Cafagna
  9. Giuseppe De Palma
  10. Antonio Tufaro
  11. Vito Michele Garrisi
  12. Maria Chironna

Reviewed by

Read the full article See related articles

Listed in

Log in to save this article

Abstract

Real-time polymerase chain reaction (RT-PCR) testing for the identification of viral nucleic acid is the current standard for the diagnosis of SARS-CoV-2 infection, but technical issues limit its utilization for large-scale screening. Serological immunoglobulin M (IgM)/IgG testing has been proposed as a useful tool for detecting SARS-CoV-2 exposure.

Objective

The objective of our study was to compare the results of the rapid serological VivaDiag test for SARS-CoV-2–related IgM/IgG detection with those of the standard RT-PCR laboratory test for identifying SARS-CoV-2 nucleic acid.

Methods

We simultaneously performed both serological and molecular tests with a consecutive series of 191 symptomatic patients. The results provided by a new rapid serological colorimetric test for analyzing IgM/IgG expression were compared with those of RT-PCR testing for SARS-CoV-2 detection.

Results

Of the 191 subjects, 70 (36.6%) tested positive for SARS-CoV-2 based on RT-PCR results, while 34 (17.3%) tested positive based on serological IgM/IgG expression. Additionally, 13 (6.8%) subjects tested positive based on serological test results, but also tested negative based on RT-PCR results. The rapid serological test had a sensitivity of 30% and a specificity of 89% compared to the standard RT-PCR assay. Interestingly, the performance of both assays improved 8 days after symptom appearance. After 10 days had passed since symptom appearance, the predictive value of the rapid serological test was higher than that of the standard molecular assay (proportion of positive results: 40% vs 20%). Multivariate analysis showed that age >58 years (P<.01) and period of >15 days after symptom onset (P<.02) were significant and independent factors associated with serological test positivity.

Conclusions

The rapid serological test analyzed in this study seems limited in terms of usefulness when diagnosing SARS-CoV-2 infection. However, it may be useful for providing relevant information on people’s immunoreaction to COVID-19 exposure.

Article activity feed

  1. Version published to 10.2196/19152
  2. ScreenIT

    SciScore for 10.1101/2020.04.03.20052183: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIACUC: The study has been approved by Ethical Committee of IstitutoTumori G Paolo II, IRCCS, Bari with Protocol number CE 870/2020.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    A surface antigen from SARS- CoV-2 which can specifically bind to SARS-CoV-2 antibodies (including both IgM and IgG) is conjugated to colloidal gold nanoparticles and sprayed on conjugation pads.
    SARS-CoV-2
    suggested: None
    The SARS-CoV-2 rapid IgG-IgM combined antibody test strip has two mouse anti-human monoclonal antibodies (anti-IgG and anti-IgM) stripped on two separated test lines.
    anti-human monoclonal antibodies
    suggested: None
    anti-IgG
    suggested: None
    As the specimen flows through the device, anti-SARS-CoV-2 IgG and IgM antibodies, if present in the specimen, are bound by the SARS-CoV-2 antigen labeled gold colorimetric reagent fixed on the conjugate pad.
    anti-SARS-CoV-2 IgG
    suggested: None
    As the conjugated sample continues to travel up the strip, the anti- SARS-CoV-2 IgM antibodies are bound on the M(IgM) line, and the anti-COVID-19 IgG antibodies are bound to the G (IgG) line.
    anti- SARS-CoV-2 IgM
    suggested: None
    anti-COVID-19 IgG
    suggested: None
    The presence of SARS- CoV-2 IgG and IgM antibodies are indicated by a red/purple line in the specific region indicated on the device.
    IgM
    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:
    Such a behavior in the 6-10 day time window after symptom appearance is accompanied by an improvement in serological test sensitivity compared to standard molecular testing Our study has some important limitations. Firstly, the Viva-Diag™ test is based on a colorimetric evaluation of the IgG and IgM bands by the operator thus implying all the limitations that a qualitative inter-intra-operator evaluation produce in terms of variability (15). In our study, this aspect was partially solved by resorting to double operator evaluation and taking picture of all test results to be re-analyzed by a third party in the case of first level evaluation disagreement. However, in this regard, our next step of research to overcome the issues met,will be to use quantitative immunoenzymatic methods to analyze SARS-CoV-2 specific immunoglobulins (16). A further limitation of our study regarded the fact that the neutralizing antibodies used in the Viva-diag™ test might cross-react with other corona-virus antigens, like those of the SARS-CoV. The recombinant antigen utilized in Viva-Diagis the receptor binding domain of SARS-CoV-2 spike protein for which information on possible cross-reactivity with other corona and flu viruses has not yet been studied (9). Further studies are urgently needed to definitely clarify this point.

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

    IdentifierStatusTitle
    NCT04316728Not yet recruitingClinical Performance of the VivaDiag ™ COVID-19 lgM / IgG Ra…

    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 10.2196/preprints.19152
  4. Version published to 10.1101/2020.04.03.20052183v1 on medRxiv