Sensitivity and specificity of a rapid test for assessment of exposure to SARS-CoV-2 in a community-based setting in Brazil

  1. Lucia Campos Pellanda
  2. Eliana Márcia da Ros Wendland
  3. Alan John Alexander McBride
  4. Luciana Tovo-Rodrigues
  5. Marcos Roberto Alves Ferreira
  6. Odir Antônio Dellagostin
  7. Mariangela Freitas da Silveira
  8. Aluisio Jardim Dornellas de Barros
  9. Pedro Curi Hallal
  10. Cesar Gomes Victora

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Abstract

Background

While the recommended laboratory diagnosis of COVID-19 is a molecular based assay, population-based studies to determine the prevalence of COVID-19 usually use serological assays.

Objective

To evaluate the sensitivity and specificity of a rapid diagnostic test for COVID-19 compared to quantitative reverse transcription polymerase chain reaction (qRT-PCR).

Methods

We evaluated the sensitivity using a panel of finger prick blood samples from participants >18 years of age that had been tested for COVID-19 by qRT-PCR. For assessing specificity, we used serum samples from the 1982 Pelotas (Brazil) Birth Cohort participants collected in 2012 with no exposure to SARS-CoV-2.

Results

The sensitivity of the test was 77.1% (95% CI 66.6 - 85.6), based upon 83 subjects who had tested positive for qRT-PCR at least 10 days before the rapid diagnostic test (RDT). Based upon 100 sera samples, specificity was 98.0% (95% CI 92.9 - 99.8). There was substantial agreement (Kappa score 0.76) between the qRT-PCR results and the RDT.

Interpretation

The validation results are well in line with previous assessments of the test, and confirm that it is sufficiently precise for epidemiological studies aimed at monitoring levels and trends of the COVID-19 pandemic.

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  1. ScreenIT

    SciScore for 10.1101/2020.05.06.20093476: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementConsent: All participants signed an informed consent form.
    RandomizationSamples from healthy individuals (n = 100) were randomly selected from a pre-COVID-19 serum collection from 3,700 individuals belonging to the 1982 Birth Cohort Study [16] and stored at the Epidemiology Research Centre, Federal University of Pelotas (UFPel, Pelotas, RS).
    BlindingThe test was developed for 15 minutes at room temperature and the results (positive or negative) were read by independent experienced readers blinded to the sample status.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    At least 10 days later (to allow for the production of anti-SARS-CoV-2 antibodies), the study participants were invited to complete a questionnaire on their COVID-19 symptoms and demographic information.
    anti-SARS-CoV-2
    suggested: None
    Software and Algorithms
    SentencesResources
    Statistical analyses were performed using MedCalc for Windows, version 19.2 (MedCalc Software, Ostend, Belgium).
    MedCalc
    suggested: (MedCalc, RRID:SCR_015044)

    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:
    Some limitations of our study merit discussion. First, we included two different samples to study sensitivity (individuals with previous positive qRT-PCR) and specificity (sera from the Pelotas Cohort Study). Both samples are similar in percentage of self-reported skin color, but the specificity sample was younger. Also, only the second sample is population based. Although sensitivity and specificity are intrinsic diagnostic properties of the test and theoretically do not vary with prevalence, it is important to consider that our positive sample set may not be representative of the entire spectrum of disease. However, it included both symptomatic and asymptomatic individuals at the time of testing, representing an important population regarding the need of testing. This means that the test may have even higher accuracy in more serious disease. The second limitation is inherent to the reference method. The reference method based on qRT-PCR to detect the presence of SARS-CoV-2 in nasofaringeal swabs collected from patients suspected to have COVID-19 is highly dependent on the quality and timing of sample collection [3,5,7]. When the reference test does not present with 100% specificity or sensitivity, true results of the study test may be interpreted as false. This may happen specially when the NAAT fails to detect disease, and qRT-PCR false negatives may result in misinterpretation of a RDT positive result. It is also important to emphasize that NAATs and RDTs are designed to ...

    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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  2. Version published to 10.1101/2020.05.06.20093476v1 on medRxiv