The highly anticipated home saliva test for COVID-19 is now more of a fiction than a reality. Hopes of introducing an antigen-based test at home to contain the spread of the coronavirus are dwindling as an effective test is pending creation, according to the New York Times.
While it's still possible – Columbia University researchers say they're into something – this type of test has a few problems. Public health experts who have watched some companies' efforts to develop spit tests argue that saliva tests are relatively new to science and now is not the time to focus on them. At least two companies, E25Bio, which is affiliated with the Massachusetts Institute of Technology (MIT) and OraSure Technologies, Inc. in Bethlehem, Pennsylvania, had quick tests at home but have since focused on researching and making flat nasal swabs, according to data the Times.
Testing with saliva has been problematic in the past. For starters, saliva tests need to be more specific about their goal. Saliva levels can change in a single day, making it difficult to ensure consistent use of the test. A study by Sichuan University in China found that diagnosing COVID-19 through saliva tests depends on where the saliva in the throat is coming from.
Another problem is whether the sample is clean. For example, the University of Illinois ran tests to see if there was food, blood, or oral hygiene products in the saliva. One of the hardest things about saliva testing is that saliva isn't always clean – researchers have found problems with it clumping or sticking to the sides of test tubes.
With the focus primarily on flat nasal swabs, the race for approval has increased. The flat nasal swab test developed at MIT has been tested with 93% accuracy, with researchers testing both positive and negative COVID samples.
Another test that looks for the genetic material of the virus has been shown to be very accurate. Using a technology called PCR (polymerase chain reaction), this test does not detect early viral infection, only active infection. It also takes a few days before the results can be evaluated. Samples can also be taken from the neck.
Columbia University researchers have developed a rapid saliva test that, according to initial data, is effective in 96% of cases. However, it is not intended for home use as the test is not cheap and includes devices that the Times says are not consumer-friendly. While more testing is required, Columbia has asked the Food and Drug Administration (FDA) for an emergency clearance.