Update Nov. 18, 2020: As of today, swish and spit testing is now being offered to adults in addition to children. Read about the B.C. researchers who developed the test here.
BY PAMELA FAYERMAN
B.C. residents seeking COVID-19 testing can now provide a spit sample instead of having the deepest reaches of their noses and throats probed and swabbed.
The gold standard for COVID-19 testing is nasopharyngeal swabs but there’s a growing global shortage of swabs and plenty of variability in how they are used at drive-through and other test stations, contributing to higher than desired false-negative rates.
Preliminary research published since March has shown that spit sampling is almost equal in accuracy to swabs. (A meta-analysis can be read here). There are other benefits as well. They are non-invasive tests said to be safer for healthcare workers because there’s no face to face contact with testing subjects. As well, throat or nasal swabs are uncomfortable and can induce gagging and coughing in testing subjects; which can expose healthcare workers to potential COVID-19 infections.
In a previous post, I wrote about the fact that COVID-19 has hit healthcare workers hard. About a quarter of all infections have been among those working in healthcare.
Self-collected gargle samples could also be done at home or they could also be conducted like urine testing; individuals go in a room, gargle with a saline solution and then leave their sputum sample in a jar or a tube on a designated surface.
Some research has shown that for other respiratory infections, the detectable viral load is higher in spit samples than it is in swabs. A Mayo Clinic infectious disease discussed spit testing here.
In Alberta, many COVID test collection sites and facilities have transitioned to throat swabs after an evaluation showed that throat swabs are easier to perform and equivalent in sensitivity and specificity to nasal swabs. But Dr. Mel Krajden, medical director of the BC Centre for Disease Control laboratory, said rather than going down that path, B.C. is “exploring” saliva testing.
Experts like the fact that such tests can be obtained without close contact between a patient and a health worker which also means that personal protective equipment could be preserved. In England, a massive experiment using the spit tests got underway earlier this summer.
Gargle samples have been used in Germany and an article published online in Infection Control and Hospital Epidemiology by Cambridge University Press describes the generally positive experience and benefits.
The article is based on experience in German hospitals where gargle specimens were used for the detection of COVID in health care workers. Hospitals set up designated rooms and those who had symptoms or exposure to a COVID patient would provide a sample in a room equipped with a test kit. Gargling time was 10 to 30 seconds. The closed container was left in a room and then transferred to a laboratory. There was no difference in accuracy between throat swabs and gargle samples and hundreds of PPE sets didn’t have to be used over a period of 25 days. As well, the spit tests replaced 1,000 swabs.
While the authors acknowledge that more testing should be done, they concluded that saliva tests are a worthwhile alternative:
“Self-collected gargle samples are easy to take, noninvasive, material saved, and safe for healthcare workers.”
The Food and Drug Administration has given approval for some American-developed saliva tests, generally intended to be used at home and then taken or mailed to a test centre.
One caveat is that individuals have to be able to gargle; some can’t, like infants and young children, or those with medical issues like dementia.
If you are going to take a swish and spit test, you cannot eat, drink, smoke, or brush your teeth brushing one hour prior to the test.