Rapid tests more sensitive when throat and nose swabbed: Science Table

The Ontario COVID-19 Science Table has weighed in on the sensitivity of rapid tests to the Omicron variant, and the best way to use them.

The Science Table said that in general, the available rapid tests are less sensitive to Omicron than the Delta variant when swabbed nasally, particularly in the first day or two after infection. While this isn’t ideal, the Science Table said that if people swab their nose and throat, the test sensitivity for detecting COVID-19 is increased.

Rapid tests can be a helpful tool, but the Science Table emphasizes that a single negative rapid test is not reason to throw caution to the wind.

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“A single negative rapid antigen test result cannot reliably rule out infection; a single negative test result is not conclusive and should not be used as a green light for abandoning or reducing precautions,” the Science Table advised in a briefing.

However, a single positive rapid test result is reason to isolate and assume infection, the Table advised.

The Science Table compared data on rapid test sensitivity and found that the rapid tests sensitivity to the detection of Delta was 81%, while the sensitivity to detection of Omicron was just 37.1%.

Ontario COVID-19 Science Advisory Table

Studies indicate that swabbing both the throat and the nasal passages might help increase rapid test sensitivity. One example used by the Science Table shows sensitivity increase from 68.4% from a nasal-only swab to 81.6% when nose and throat are swabbed.

So, how should you use rapid tests?

The Science Table suggests beginning by swabbing inside both cheeks and the back of the tongue or throat, and then swab the nostrils. Reversing this order could result in an unpleasant-tasting swab. You might gag when sticking the swab near the back of your throat, but the Science Table says that’s fine.

“Swabbing the back of the tongue or throat may induce a gag reflex, which is not dangerous and actually indicates that the location of the swabbing was appropriate,” the briefing reads.

Ontario had deployed free rapid test kits in many retailers across the province. There are more than 2,300 locations where they can be picked up. There is a limit of one kit (five tests) per household while supplies last.