PoP BC Briefing #3- Testing Strategies for Success

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POP BC Briefing #3: Testing Strategies for Success

How can COVID-19 testing be used as a strategy to end the pandemic? What is the difference between rapid tests and PCR tests? How are rapid tests useful, and how are they used in other jurisdictions to allow people to congregate safely? And what is BC’s testing situation, and what can be done better so BC can drive COVID-19 transmission down so we can participate in our daily lives safely, while also protecting the health care system?

Facilitator: Melody Ma, Community Rapid Testing advocate, UBC Medical Laboratory Science

Speakers:

  • Dr. Victor Leung, Infectious Disease physician and medical microbiologist specializing in infection prevention and control and antimicrobial stewardship
  • Dr. Paul Tupper, Professor, Department of Mathematics, SFU. Member of the BC COVID-19 Modelling Group
  • Dr. Lisa Barrett, MD, PhD Clinician Investigator and Infectious Disease specialist, Dalhousie University, Department of Medicine. Pioneer of rapid testing programs in the community in Nova Scotia
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Highlights from this briefing

Dr. Leung reveals the drawbacks of relying exclusively on PCR testing for detecting cases that lead to community spread.
Dr. Tupper talks about the usefulness of Rapid Antigen Testing (RAT) in the containment of school-based outbreaks of COVID-19.
Dr. Barrett discusses how rapid antigen testing has been used effectively as a tool of community engagement in Nova Scotia.
Dr. Leung discusses the issues with relying on PCR testing, which is most effective after the most infectious period of COVID transmission.
Dr. Leung points out that in every aspect other than the narrow metric of test sensitivity of an individual test, rapid antigen tests perform better than PCR tests.
BC is not using all the tools provided by the federal government to detect cases before they lead to community transmission. Dr. Barrett responds.

Summary of Key Points

  • There are different types of COVID tests, which answer different questions.
  • Tests can help protect people in many ways.
  • Rapid tests should be widely available in BC, as they are in Nova Scotia

What are the different types of tests?

PCR vs Rapid testing comparison

PCR or RT-PCR (Reverse Transcriptase -Polymerase Chain Reaction) detects small pieces of the virus, even after the infectious period is over. This is the lab test.

PCR tests answer the question, Does this person have COVID? It is the gold standard to diagnose a person with COVID. The test is conducted with a deep nose swab or a saliva sample. In a hospital setting, it can take hours to get results. At testing sites, the results can several days. A PCR test can be positive long after a person is no longer contagious.  

It can be hard to access these tests as many BC testing sites have been closed.  In many areas you must now schedule a test. Travelling to the test exposes others to COVID since you may be spreading it to others while you wait for your result. The extra pressure of isolation while waiting for results is a huge burden.

RAT (Rapid Antigen Testing) requires a significant amount of the virus to be present, unlike the PCR test, which can detect even small amounts of virus RNA.

This test answers the question, is this person infectious with COVID?  This is a shallow nose swab, and can be done anywhere since no lab is required.  Results are ready in 15 minutes. It can detect the virus before symptoms start, and also in the peak infectious stage. 

You can isolate immediately if you find you have COVID and you don’t interact with others while travelling to or getting tested. False negative tests happen. You can repeat the test in a day or two or get a PCR test if you still have symptoms and a negative RAT test. False positive tests are rare.


How can BC make better use of testing?

The infectious period of COVID precedes the onset of COVID symptoms

More than half of COVID transmissions happen before a COVID+ person has symptoms.  Rapid tests can detect COVID before people feel sick.

If staff at acute care hospitals and long term care homes were regularly screened with rapid testing, we could reduce outbreaks in these facilities. Dr. Tupper reports that rapid testing in long term care homes could prevent 50% of the infections brought in by staff. 

Rapid testing is also useful at homeless shelters and other places where people live or work close together to help reduce community spread. 

In schools, we could rapid test children who were exposed to a student with Covid-19 to determine whether or not they should stay in school.  Regular testing of whole classrooms is conducted in Germany. RATs detect exposure as early as possible.

People could use rapid tests to self-screen before visiting grandparents, families with a new baby, or others who are at higher risk if they become infected.  

Engaged Communities is a BC non-profit organization that delivers tests to be used at home in COVID hot spots, in partnership with Fraser Health Authority.


Are other provinces using rapid testing more effectively than BC?

Dr. Lisa Barrett shares her experience in Nova Scotia as a champion for the community use of Rapid Antigen Tests. The effort has involved thousands of people, the government, Public Health, the Nova Scotia Health Authority, and many community members. During the third wave, widespread use of community RAT by trained community members detected 20% of early cases, allowing the wave to peak and come down early.  Community members organized and offered asymptomatic rapid testing wherever there was community spread.

Since the spring of 2021, rapid testing has been used in vulnerable sectors like shelters, public housing, and more recently, universities and schools.  In rural areas that are far from a PCR testing site, RATs can be used with symptomatic children to avoid travelling for days, requiring parents to take time off from work. If the test is positive, it should be confirmed by PCR.

Nova Scotia is also distributing thousands of repackaged individual Pan Bio rapid tests, allowing people to test at home and self-regulate their reporting. The province has a low threshold, low barrier testing system. No appointment is needed to get a PCR test anywhere that RATs are distributed or administered.  Dr. Barrett recommends that other provinces such as BC start using RATs.

“Just do it, limit less, empower more. Let people lead in the community. It will pay off in building trust, engagement and involvement.”


Why should we use more rapid testing in BC?

Vaccines alone are not enough to end the pandemic. Testing helps us get together safely, and helps keep COVID out of our workplaces and schools. Testing helps us detect who is infectious and isolate them quickly in order to break chains of transmission. Testing also helps us know who has COVID 19 so we can track its long-term effects and learn more about this new disease.

Rapid Antigen Testing is an effective Public Health tool.  We have free tests provided by the Federal Government. We need better access to this important layer of protection.

Addendum, December 2021:

RAT can be used with the Omicron variant, but because of the virus’s rapid doubling time, testing should be performed as close in time to an in person meeting as possible. To increase detection of COVID antigen and improve the test sensitivity, experts in the UK, which has extensive experience with RATs, recommend swabbing both the throat and the nose. Use the same swab to sample first the throat and then the nose.

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