Western Testing Centre (2)

Western's mobile testing centre is now closed and students can get a COVID-19 test at the Rec Centre.

In the wake of the latest coronavirus outbreak at Western, the interminable hours of waiting at campus testing locations rivals the infamous UCC Tim Horton's lineups of the past.

Receiving a negative test result after all those nail-biting hours often trigger side effects including shouts of joy, festive moods and care-free attitudes. But, these tests may not be as reliable as you might think.

Tests are considered effective based on two criteria: specificity and sensitivity. In general, COVID-19 tests are highly specific but have poor sensitivity — in other words, a positive result can be trusted, but a negative result may be wrong.

The most popular test today is the reverse transcriptase polymerase chain reaction-based SARS-CoV-2 test, also known simply as the RT-PCR test. The university uses the RT-PCR test, according to Matt Mills, director of Health, Safety & Wellness at Western.

It is widely accepted as the most specific and sensitive test available for COVID-19, but a recent review by the American College of Physicians has exposed its greatest flaw.

The test is time-sensitive; the time between potential exposure to the virus and getting tested significantly affects the sensitivity of the test. The optimal time to be tested is eight days after initial exposure to a potential COVID-19 case or, on average, three days after showing symptoms.

The test's sensitivity is still poor even at this optimal time. The probability of a false-negative result in an infected individual at this time is 20 per cent — so, if everyone is tested at the optimal time, two out of 10 people will receive false negatives.

Sensitivity of the test decreases dramatically outside of the optimal window of time. For example, getting tested as soon as possible may seem like a good idea, but the results from those tests are useless — the probability of a false-negative on the first and second day is 100 per cent and 90 per cent, respectively.

Though the sooner people with the virus get tested, the more effective contact tracing can be according to the Middlesex-London Health Unit.

The federal government is investing in a new, faster test: the Abbott ID NOW rapid testing device. This test is expected to take 15 minutes to complete, compared to the 50 minutes needed for PT-PCR testing.

While many people see this as a step forward in our fight against the pandemic, a study by the Columbia University Irving Medical Center has shown that the sensitivity of this “rapid testing” device is significantly lower than PT-PCR testing. As a result, it is less likely to detect an infection in people with lower viral concentrations.

Infected individuals with lower viral concentrations may be less likely to spread the disease to others, but the widespread use of these devices could lead to poor contact tracing and could instill a false sense of security in infected individuals who receive negative test results.

The best thing students can do is to be critical of their actions and take precautions to stay safe and healthy — no matter which test is used.


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