London-based researchers are warning the instructions for most COVID-19 nasal swabs don't direct the user to swab deep enough.
Western University and Lawson Health Research Institute scientists studied the instructions being provided by public health officials across the country. What they found was that fewer than a quarter of provincial and territorial public health instructions tell the medical professional inserting the swab to extend it far enough to reach the nasopharynx.
"As a surgeon who works inside the nose all the time, I was surprised to find that most of the instructions in Canada aren’t effective to reach the nasopharynx; they just don’t go deep enough into the nasal cavity,” Dr. Leigh Sowerby, an otolaryngologist and associate professor at Western and Lawson scientist, said in a statement.
The nasopharynx is the upper part of the pharynx at the top of the throat behind the nose. Samples taken from that region are considered the gold standard for COVID-19 testing as they provide the most accurate results.
Sowerby and his team found practitioners in Ontario, the Northwest Territories, Nunavut, Saskatchewan, Prince Edward Island, and Alberta are being directed to only insert the swab four centimetres inside the nose, about half the distance from nostril to ear. At this depth, the swab only reaches mid-way through the nasal cavity and does not hit the nasopharynx, said Sowerby.
Instructions in British Columbia and Manitoba recommended inserting the swab deeper, about seven-centimetres in, but that too isn't far enough to reach the nasopharynx.
The only provinces and territories listing a deep enough insertion depth are Nova Scotia, Newfoundland, New Brunswick, and Yukon.
"If we are doing what we are calling a nasopharyngeal swab, the technique for that should be standardized; there is no reason why there should be so much variability,” said Sowerby. “The take-home message is that if we want the most accurate test results, there is room for improvement in the test instructions.”
The findings of the COVID-19 testing instructions study have been published in the Journal of Otolaryngology – Head & Neck Surgery.
