The Science of COVID-19 Testing


Alberta’s testing program for COVID-19 is a critical part of the province’s pandemic response, helping to determine who has COVID-19 in order to track the virus and prevent its transmission.

Alberta Precision Laboratories (APL), Alberta’s publicly funded lab service, leads the COVID-19 testing program. APL processes thousands of COVID-19 tests every day, and has completed more than six million tests since the pandemic began in early 2020.

Several different methods are used for testing Alberta’s population for COVID-19, based on the evolving needs of public health officials and the development of new technology. APL’s medical-scientific teams are constantly assessing and validating new diagnostic testing methods, in collaboration with other provincial and federal labs across the country, academic experts and private-sector partners.

The primary methods of COVID-19 testing in Alberta are:

Polymerase Chain Reaction (PCR) Testing

Watch a ‘behind the scenes’ tour of the PCR testing process at APL’s provincial lab.

The foundation of Alberta’s COVID-19 testing program is lab-based polymerase chain reaction (PCR) testing, which is used to determine if someone is currently infected with SARS-CoV-2, the virus that causes COVID-19. PCR testing is a highly sensitive molecular testing technique that is considered the gold standard for testing large populations and is used in testing programs around the world.

PCR testing is capable of detecting tiny amounts of the virus’s genetic material if it is present in a sample. The main steps involved in PCR testing are:

Sample collection – Individuals who qualify for a COVID-19 test must visit a local assessment centre, where trained health care providers take samples with a swab inserted into a person’s nose or throat. Swab samples are placed in a liquid media and are then transported to centralized lab facilities for testing.

Extraction process – Each swab sample is treated with chemicals (referred to as ‘reagents’) and placed in specialized equipment that is used to break down cellular material and viral coatings to expose the genetic material of any virus that is present in the sample. Extraction reagents contain specially engineered magnetic particles that bind to the small amount of ribonucleic acid (RNA) contained in each SARS-CoV-2 virus and separate them from the surrounding material. A significant portion of APL’s extraction reagents are supplied by an Edmonton-based company that uses made-in-Alberta technology.

Amplification process – The extracted material is placed into a new tube with different reagents, and placed in a machine to undergo the PCR process. The PCR ‘reaction’ makes millions of copies of the virus’s RNA. This process is repeated several times, allowing even a small amount of virus to be detected if it is present in a sample. A sample that is found to contain any genetic material of SARS-CoV-2 is considered positive, while a test where no genetic material is detected is considered negative.

Result notification – Each COVID-19 test result is entered into the lab computer system, and individuals are sent their test result via text message, automated phone call, and through the Alberta government’s MyHealth Records online portal. Individuals typically receive their test result within 24-48 hours of having their swab sample collected. Results from tests conducted in emergency departments, urgent care and hospital facilities will be provided directly to patients by their physicians. Everyone must follow Alberta public health requirements for self-isolation while awaiting results of their test, and after their have received their test result.

Frequently Asked Questions about PCR Testing

Q: Can I test positive for COVID-19 if I just have the flu (influenza?)

A: No. The test for COVID-19 is specific to the SARS-CoV-2 virus and cannot be mistaken for the influenza virus. In addition, those receiving a COVID-19 test at AHS assessment centres are not being tested for influenza and would not be tested for it without their knowledge and consent.

Q: Does the COVID-19 test work on people with no symptoms?

A: Yes. PCR testing will detect very small quantities of the virus, if it is present in an individual’s sample. Some people can be actively infected with COVID-19 and not show any symptoms of the disease.

Q: Is it possible to receive a false negative or false positive COVID-19 PCR test?

A: False negative and positive test results are possible but are extremely rare. False negatives can occur if swab samples are done incorrectly and don’t pick up virus that can be detected. False positives can be the result of contamination of an individual’s sample. If any questions are raised about a result potentially being a false positive or negative, we conduct a thorough investigation as part of our quality assurance process.

Q: How many cycles are used in the amplification process, and what is the cut-off threshold for determining a positive result?

A: The number of amplification cycles required to determine whether a COVID-19 sample is positive generally ranges from 15 to 35 cycles, but the threshold is dependent on many factors specific to each test platform, the equipment being used, as well as the quality of the samples being tested.

Q: How can I be tested for COVID-19 if I don’t qualify for testing through the provincial testing program?

A: Publicly funded PCR testing is not available for individuals without symptoms who require proof of negative tests for the purposes of travel, entering public places, as a condition of employment, or for general screening purposes. Individuals who do not meet the criteria for public testing can access private testing through a variety of providers for a fee. Private-sector testing providers in Alberta include DynaLIFE Medical Labs, Numi Health, Equity Health Services and some pharmacies.

Rapid Point-of-Care Testing

Learn more about the rapid point-of-care testing process.

Rapid point-of-care testing is an important pillar of Alberta’s COVID-19 testing program, providing faster diagnosis of patients that helps reduce transmission of the virus in communities. Rapid point-of-care testing provides patients with results in a matter of hours instead of a day or two required for conventional lab testing. It is particularly useful for testing in rural, remote locations where it reduces the need to transport samples to centralized labs for analysis, as well as high-volume urban assessment centres.

Rapid point-of-care testing systems have been provided to Alberta by the Public Health Agency of Canada and are approved by Health Canada for use on patients who are within the first week of showing symptoms of COVID-19. The systems have been deployed across the province at COVID-19 assessment centres, hospital labs, homeless shelters, and in mobile testing units that are visiting congregate living facilities, schools and worksites where outbreaks are suspected. Thousands of rapid tests are also being used for asymptomatic screening in all long-term care and supportive living facilities, as well as some correctional and congregate living facilities.

Those members of the public who qualify for COVID-19 testing may be given the option to receive a rapid test when they arrive at a local assessment centre. Everyone receiving a rapid test at an assessment centre will be required to provide two swab samples, in case confirmation of a negative result is required.

We continue to identify more sites and additional uses for rapid point-of-care testing across Alberta, as part of the overall pandemic response.

Rapid Antigen Tests for At-Home Use and Workplace Screening

The Government of Alberta is providing free COVID-19 rapid antigen testing kits for at-home use. They are available, while supplies last, at select AHS sites and pharmacies across the province, as well as through some workplaces and schools. For more information, including instructions for performing the tests, visit the Alberta Health website.

Answers to common questions about At-Home Rapid Antigen Tests are available.

Employers and service providers wanting to offer rapid screening tests for their employees, contractors, or clients also have the opportunity to privately purchase tests or apply to Alberta Health to receive free rapid test kits for use in their organization. These tests must be completed in accordance with the Guidelines for Employer-initiated COVID-19 Testing.

Frequently Asked Questions about Rapid Point-of-Care Testing

Q: How quickly do patients receive their rapid test results?

A: The notification process for patients receiving rapid testing at assessment centres is:

  • If the test is positive, they will receive their result by text message or call within 1 to 3 hours directing them to self-isolate. They must follow all the required steps for self isolation and contact tracing following a positive result.
  • If their test was negative, it is insufficient to rule out COVID-19 and requires further analysis in the lab for confirmation. They will receive a text message or call within 5 to 6 hours directing them to continue to isolate until you receive a follow-up text message or call with the confirmed test result, typically within 48 hours.

Q: Why do negative results from rapid tests need to be confirmed by PCR testing?

A: APL undertook significant work to validate the sensitivity of rapid testing systems, to determine how sensitive they are compared to our existing lab-based PCR testing process. Our evaluations have shown that the rapid point-of-care testing systems are less sensitive than PCR testing, so we are requiring confirmation of negative test results to ensure positive cases are not being missed.

Q: How accurate are rapid tests compared to PCR tests?

A: Our evaluations through the clinical pilot phase showed that they provide between 80 and 90 per cent sensitivity compared to lab-based PCR testing. That means we could expect as much as one in every five cases of COVID-19 to be missed using rapid testing alone, which is why we have been requiring all negative results to be confirmed in the lab.

Q: How many rapid tests has Alberta received from the federal government?

A: Alberta has received more than two million rapid point-of-care tests from the Public Health Agency of Canada.

Genetic Sequencing & Variant Screening

Lab scientist Sandy Shokoples will never forget the dismay of discovering Alberta’s first case of COVID-19. Sandy and the team at Alberta Precision Laboratories have been on a journey hunting the ever-changing virus ever since.

APL has been actively monitoring the genetic code of SARS-CoV-2 in Alberta since the beginning of the pandemic to understand how the virus is evolving in our population and to detect the arrival of variant strains from outside the province. By monitoring the virus’s entire genetic code, and sharing this information with national and international health authorities, we are able to identify and track strains that may pose new challenges for diagnosing and treating the disease in our community.

New variant COVID-19 strains identified as the Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617) and Omicron (B.1.1.529) have been classified as Variants of Concern because they appear to spread more easily than other strains. They have since spread to many other countries around the world, including Canada. The first case of a Variant of Concern in Alberta was the B.1.1.7 strain, which was identified by lab testing on Dec. 25, 2020.

All of APL’s COVID-19 testing methods are capable of detecting all known strains of the virus, but additional testing of positive cases is required to identify whether a patient is infected with a specific variant. APL has developed its own PCR tests that are used to screen positive test results for variants of concern. In addition, hundreds of selected samples are subject to full genome sequencing each week, to monitor for new mutations. Variant cases of COVID-19 are publicly reported by Alberta Health.

PODCAST: Learn more about APL’s work tracking the genetic evolution of COVID-19 in this podcast series by Genome Alberta.

Frequently Asked Questions about Genetic Sequencing & Variant Screening

Q: How long does it take to test for variants of concern?

A: Positive COVID-19 samples are sent for screening tests for the presence of mutations associated with the variants of concern. All samples that are found to contain these mutations are immediately forwarded to public health officials for contact tracing purposes.

It takes approximately 24 hours to complete an initial COVID-19 test, follow-up screening tests for variants of concern take 2-3 days.

We continue to conduct full genetic sequencing on hundreds of variant samples each week to monitor for other variant strains. Results of full genetic sequencing tests typically take 2-3 weeks.

Q: How are you testing for the Omicron variant of concern?

A: APL is prioritizing non-Delta variant cases for genetic sequencing, as Omicron is a relative of the Alpha variant (B.1.1.7) and shares some of the characteristic mutations that are identified by our PCR screening tests for variants. Non-Deltas are being sequenced using rapid sequencing technology that takes 4-5 days to complete, in addition to full genome sequencing that takes 2-3 weeks.

Q: Are patients notified if they test positive for a variant of concern?

A: Positive results for variant screening tests are reported to healthcare providers, Public Health and Infection Prevention and Control, but will not be provided directly to patients. Public health measures in place to prevent and manage spread of the virus are now based on Variants of Concern being widespread in our community, and patients should follow the directions for self-isolation and contact tracing as soon as they receive their initial positive test result.

Serology (Blood) Testing

Serology testing examines a person’s blood to see if they have generated antibodies in response to being infected by the COVID-19 virus. It takes about one to three weeks following an infection for your body to make antibodies, therefore serology testing is only used to identify past exposure to virus and is not used for diagnosing current COVID-19 infections.

Serology testing is not used for diagnostic purposes but is currently being used for surveillance and research purposes to assess the number of people in Alberta who have been exposed to SARS-CoV-2 and to inform some medical treatment decisions. It is not available to the general public in Alberta, and tests must be ordered by a physician and approved by provincial virology experts. More information about serology testing.

Frequently Asked Questions about Serology (Blood) Testing

Q: How can my doctor order serology testing for COVID-19?

A: Serology testing must be ordered by a physician and approved by the provincial Virologist-On-Call. More information for healthcare providers is available in the Updated: Serology Testing for COVID-19 lab bulletin.

Q: Can I receive a serology test outside of the provincial healthcare system?

A: Yes, various private-sector lab services provide fee-for-service serology testing in Alberta.

Q: If I have antibodies for COVID-19, does that mean I am immune to it?

A: A positive serology does not mean you are immune to COVID-19. At this time, there is a lack of evidence on whether having antibodies to COVID-19 means you are protected against reinfection with COVID-19 and if so, how long that protection would last.