American neurooncologist and neuroscientist Robert B. Darnell from the Rockefeller University developed an in-house assay to identify positive cases in the university back in the early days of the pandemic when commercial COVID-19 tests were short supply.
Science Daily reported that the saliva testing he developed became easier and safer to administer than nasal swabs and had been used over the past nine months on the campus.
A schoolboy gives a sample during a saliva test for the COVID-19 at an elementary school in Eysines, on the outskirts of Bordeaux, southwestern France, on February 25, 2021. - The tests, which received the green light from France's High Authority of Health (HAS) on February 11, 2021, are less unpleasant than nasal swabs and have been carried out in schools and universities since the return of the winter holidays. (Photo by Philippe LOPEZ / AFP) (Photo by PHILIPPE LOPEZ/AFP via Getty Images)
Saliva Testing: Inexpensive Answer to Nasal Swab Tests
The nasopharyngeal swab is the main means for collecting samples for testing COVID-19. According to News Medical Life Sciences, healthcare professionals administering the swab test must wear recommended personal protective equipment (PPE), which includes an N95 mask, disposable cap, goggles, gown, latex gloves, and shoes.
They would insert a swab into the nose while the patient is sitting upright and their head straight. The swab could freely move into the nasal cavity without obstruction until it reached the nasopharynx. There, the swab is rotated gently and completes two 360-degree rotations to absorb secretions from this area.
However, this method can cause discomfort and require trained healthcare staff. As Science Daily reported, Darnel's DRUL saliva test offers a lot of advantages: it is safe, efficient, comfortable because it only requires spitting in a cup, and inexpensive as it only costs $2 per test,
The study, titled "DRUL for School: Opening Pre-K With Safe, Simple, Sensitive Saliva Testing for SARS-CoV-2," published in PLOS One, shows that the DRUL saliva test matches and outperforms widely used commercial tests.
It successfully detected a single viral particle in one microliter of saliva, comparable to most sensitive assays available. More so, the DRUL saliva test was able to detect the 30 COVID-19 positive samples that nasal swabs also detected. While it was able to detect positive samples that nasal swabs predicted to be negative.
"This research confirms that the test we developed is sensitive and safe," says Darnell, quoted by Science Daily. "It is inexpensive, has provided excellent surveillance within the Rockefeller community, and has the potential to improve safety in communities as the pandemic drags on."
DRUL saliva testing has been conducted on Rockefeller's Child and Family Center for children and employees since it was approved as a clinical diagnostic method in New York State.
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Factors That May Affect Saliva Testing Accuracy
Dr. Spencer Kroll, an internal medicine specialist in New Jersey, told Healthline that saliva testing is very sensitive and can detect the virus in a microliter of saliva. It is reassuring that these test kits are at par with PCR tests commonly used to detect SARS-CoV-2.
However, many factors could impact the accuracy of saliva testing. This includes decongestant and steroid nasal sprays, sore throat lozenges, toothpaste, mouthwash, and blood. Smoking, drinking alcoholic beverages could also cause false results as they reduce adequate specimens that the test can detect.
He noted that appropriate precautions are necessary to avoid affecting the accuracy of saliva testing. Fortunately, at-home test kits and easy-to-follow instructions can help reduce margins of error.
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