Testing, testing: the key to controlling the spread of coronaviruses

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Widespread screening for coronavirus is considered a key element in the response to the pandemic, both to diagnose infections and potentially to ease blockages.

In Canada, the provinces initially limited diagnostic tests for COVID-19 to health care workers who directly care for patients, people with severe symptoms and those who work with vulnerable groups.

Arrears are gone, but most tests are still targeted – instead of the larger, faster tests that infectious disease doctors require to control the spread.

Here is an introduction to different types of tests, and their pros and cons:

Swabs

Nasal or throat samples test for the presence of genetic material from the coronavirus. They help with diagnosis and are also important for contact detection work – those who may have been exposed to an infected person, such as family members, health workers or travelers nearby

Swabs are usually inserted into a patient’s nose and then sealed in a tube containing growth medium to support the virus until it can get to the laboratory.

WATCH | What is it like to have a nasal swab:

A look at what patients can expect if they end up in an emergency room with symptoms of COVID-19. 1:59

The sample should be collected carefully in the appropriate area. It is estimated that errors can occur about 8-10% of the time, which contributes to false negatives.

Laboratories also need specialized equipment and Qualified staff.

Provincial laboratory officials say the amount of virus in the upper respiratory tract appears to peak during the first week of symptoms and may fall too low to be detected later.

Despite the disadvantages, swabs are the gold standard for detecting coronavirus infection.

Health Canada says that only diagnostic tests it allows can be imported or sold in this country, based on a review of the evidence indicating that they will provide accurate and reliable results.

There’s no legitimate “Home test kits” available in Canada.

Office tests

“Service point” diagnostic tests use a blood bite sample rather than a nasal swab. They can be done while a patient is waiting in a doctor’s office, clinic or hospital, with results in less than an hour.

But doctors and scientists still have to determine their accuracy in the real world, as opposed to in ideal conditions in the tester’s laboratory.

Diagnostic tests do not tell whether a person has already been exposed to the virus or has successfully triggered an immune response.

Blood tests for antibodies

This is where the antibody or serological tests could enter. Instead of looking for the virus itself, these look for proteins in the blood called antibodies. Your body produces antibodies weeks after you have successfully fought an infection.

In Canada, antibody tests for COVID-19 are only a research tool and are not available to the public.

Dr. Anthony Fauci, who heads the US National Institute of Allergies and Infectious Diseases, said it was a “reasonable assumption” that if you have antibodies, you will be protected from another infection.

But scientists have yet to test this hypothesis and discover:

  • The accuracy of serological tests.
  • What levels of antibodies are needed for immunity?
  • How long does immunity last.

The researchers hope to use antibody tests to find out how far the coronavirus has spread and to determine how lethal it is.

A COVID-19 newsletter was presented at a coronavirus assessment clinic in Montreal on March 10. (Graham Hughes / The Canadian Press)

Experts say serology tests will not tell you how many antibodies your immune system has produced in response to COVID-19. This is important because immunity often depends on a high concentration of antibodies.

Health Canada said officials are vigilant to ensure that serological tests are used appropriately, in conjunction with other laboratory tests.

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