Rapid nasal antigen tests are more effective at detecting coronavirus than oral ones, according to two new scientific studies, one American and one Spanish, published in medRxiv. This reinforces the belief that tests intended for the nose should not be used orally, but should be performed according to the manufacturer's instructions.
Researchers in the United States, led by Dr. Diane Havlir of the University of California, San Francisco, performed a rapid nasal test (Abbott's BinaxNOW) and molecular tests on 731 people in January. The 296 tests (40%) were positive based on the molecular test and 99% of the infections were related to the Homicron variant.
Rapid tests detected 95% of people with a high viral load who were more likely to transmit the virus. The sensitivity of the rapid test (ie its ability to detect the virus) was lower, from 82% to 65%, the lower the viral load.
When the same rapid test was performed by taking an oral sample in 75 people, it was much less sensitive than the nasal one, failing to detect 91% (20 out of 22) of the molecular test-positive cases. nose. This was confirmed in a direct comparison in 115 subjects who underwent the same rapid test with samples from both the nose and the mouth. The sensitivity of the test was almost 98% from the nose and only 49% from the mouth.
The researchers concluded that "oral tests (neck or cheek) should not replace nasal tests because of their significantly reduced sensitivity to the nose."
A separate Spanish study conducted in Barcelona on 300 people tested Covid-19 both nasally and orally, also concluded that taking a sample orally (saliva from the inside of the cheek) is much less reliable than taking it through the nostrils in terms of coronavirus detection. Oral tests were found to have a sensitivity of only 32%.
The researchers concluded that "nasal tests perform better than oral tests" and advised "against the use of oral samples to diagnose SARS-CoV-2 coronavirus by rapid testing".
Source: RES-EAP
