How does the current lab test for COVID-19 work?

Posted on May 5, 2020 by Madalon Burnett

Summary

Laboratory identification of COVID-19 is performed through a validated nucleic acid amplification test. In Ontario, gene targets used for nucleic acid laboratory testing are the E gene, the Orf1a/b gene, the RdRp gene, and the N gene. Serologic testing for COVID-19 is not yet approved in Canada. 

I.   NUCLEIC ACID BASED TESTING

Ontario

Gene targets for the assays used in Ontario are given here (1). Information on gene targets used in other provinces could not be found. 

Assay Gene Targets
PHO Laboratory LDT E gene*
Roche Orf1a/b gene, RdRp gene
Abbott N gene, RdRp gene

E – envelope; Orf1a/b – open reading frame 1a/b; RdRp – RNA dependent RNA polymerase; N – Nucleocapsid

*Specimens may also be tested using a laboratory developed RdRp gene target assay

 

Laboratory confirmation of COVID-19 at PHO Laboratory consists of:

  • Detection of at least one genome target by real-time PCR

OR

  • One or multiple targets is/are indeterminate* by real-time PCR AND detection of COVID-19 virus by sequencing.   

PHO Laboratory testing is considered INCONCLUSIVE if:

  • One or multiple targets is/are indeterminate* by real-time PCR.

AND

  • COVID-19 is not detected (or remains indeterminate) by testing on an alternative real-time PCR assay, or on Sanger sequencing of the RdRp gene.

The E gene is the more sensitive PCR target (1).

II.   ANTIBODY TESTING

Health Canada has not yet approved serologic testing for COVID-19 (2). Neither has the BCCDC (3). As such, there is no publicly available information about what antigens (eg. spike glycoprotein etc.) will be used for antibody testing. 

Requirements for a COVID-19 Antibody Test

Cross Reactivity with Other Corona Viruses

Health Canada mandates that cross reactivity be tested for in the following viruses – a test that is cross reactive to any of these viruses will not be approved (4). 

  • Human coronavirus 229E
  • Human coronavirus OC43
  • Human coronavirus HKU1
  • Human coronavirus NL63

These four strains are the types of coronaviruses that cause common cold symptoms (5). 

For a full list of all required cross reactive testing and other specifications that any antibody test must follow to be approved in Canada, visit: https://www.canada.ca/en/health-canada/services/drugs-health-products/medical-devices/application-information/guidance-documents/covid19-requirements-serological-antibody-tests.html.

Questions? Comments? Does this need to be updated? Do you have valuable points to add ? Please email ask.reakt@ubc.ca.

References

  1. Coronavirus Disease 2019 (COVID-19) Testing | Public Health Ontario [Internet]. Public Health Ontario. 2019 [cited 2020 May 5]. Available from: https://www.publichealthontario.ca/en/laboratory-services/test-information-index/wuhan-novel-coronavirus
  2. Health Canada. Serological tests for use against COVID-19 – Canada.ca [Internet]. Canada.ca. 2020 [cited 2020 May 6]. Available from: https://www.canada.ca/en/health-canada/services/drugs-health-products/medical-devices/covid-19/serological-testing.html
  3. Common Questions [Internet]. Bccdc.ca. 2019 [cited 2020 May 6]. Available from: http://www.bccdc.ca/health-info/diseases-conditions/covid-19/common-questions
  4. Health Canada. Requirements for serological antibody tests submitted under the COVID-19 Interim Order: guidance – Canada.ca [Internet]. Canada.ca. 2020 [cited 2020 May 6]. Available from: https://www.canada.ca/en/health-canada/services/drugs-health-products/medical-devices/application-information/guidance-documents/covid19-requirements-serological-antibody-tests.html#a65
  5. Common Human Coronaviruses [Internet]. 2020 [cited 2020 May 6]. Available from: https://www.cdc.gov/coronavirus/general-information.html

Disclaimer

The above is intended to serve as a rapidly-created, accessible source of information curated by medical students and healthcare professionals. It is for educational purposes only and is not a complete reference resource. It is not professional medical advice, and is not a substitute for the discretion, judgment, and duties of healthcare professionals. You are solely responsible for evaluating the information above.