Widespread and rapid testing to detect coronavirus infections is key during the ongoing pandemic. Catching an infection early could help contain the spread of the virus and thus help save lives. Countries around the world have been frustrated over testing shortages and delays for months now. But a new saliva-based test for COVID-19 could offer a fast and inexpensive solution to millions of people.
This laboratory diagnostic test has been developed by researchers at the Yale School of Public Health and has been granted authorization from the Food and Drug Administration recently.
In a recent paper, published on August 4 on the preprint server medRxiv, a team led by Yale postdoc Chantal Vogels explained the new tool called 'SalivaDirect'. Another team, comprising of many of the same researchers, had earlier this year detailed that saliva could be collected in any sterile container and that it remained mostly stable, without the need for special tubes or preservatives.
“This is a huge step forward to make testing more accessible,” said Chantal Vogels, a Yale postdoctoral fellow, who led the laboratory development and validation along with Doug Brackney, an adjunct assistant clinical professor. “This started off as an idea in our lab soon after we found saliva to be a promising sample type of the detection of SARS-CoV-2, and now it has the potential to be used on a large scale to help protect public health. We are delighted to make this contribution to the fight against coronavirus.”
How useful is SalivaDirect?
Until now, detecting the novel coronavirus SARS-CoV-2 involved the reverse transcription-polymerase chain reaction test. This “RT-PCR” test is conducted by collecting a sample from the back of a person's nose or mouth. While effective, the nasopharyngeal swabbing is unpleasant and isn’t cheap either. However, it was chosen as the preferred sampling technique because of its effectiveness in detecting respiratory infections over the years.
Unfortunately, there’s a limit to the amount of COVID-19 testing that can be conducted through this method. This is where the new saliva-based test could be a game-changer as it promises to be quicker, cheaper, more flexible, and widely accessible. With saliva being quick and easy to collect, this test could indeed be a turning point in COVID-19 diagnostics
So far, the results have shown that SalivaDirect is highly sensitive and produces similar results as nasopharyngeal swabbing. Now, further tests are being conducted to see if the method can be successful as a test for asymptomatic individuals, too. Also, compared to nasopharyngeal swabs, the authors found a “high agreement” of more than 94 percent in detecting true positives between the two methods.
The Highlights of SalivaDirect:
Unlike some other tests that need specific supplies, the SalivaDirect test doesn't require a special swab or collection device. It can also be used with reagents from various vendors. The researchers have simplified the test so that it only costs a couple of dollars. According to the researchers, the cost per sample could be as low as $1.29 to a high of $4.37, with the addition of a saliva collection aid.
Another key step in the traditional COVID-19 testing includes extracting the virus’s RNA after the sample is collected before it can be detected by sensitive PCR-based methods. SalivaDirect removes the extraction step and replaces it with something very simple. “You add an enzyme, you heat it up, so you lose the most expensive step and the most time consuming and the most skilled [steps],” says Nathan Grubaugh, an epidemiologist at Yale and a co-author on the study.
The new test can run approximately 90 samples in fewer than three hours and has the potential to scale higher in bigger labs having automation. What’s even more encouraging is that Yale is offering SalivaDirect’s protocol open source. This means that researchers around the world can take and modify the method for use in their own labs depending on the resources they have. The Yale researchers want their protocol to be as flexible as possible to the different polymerase chain reaction (PCR) kits already available on the market.
Moreover, the saliva-based test is safer, too. In the traditional method, when the swab is inserted into the back of the throat, it often leads to a cough or a sneeze. Thus, there’s always a risk of the discharge of droplets from the person carrying the virus. With SalivaDirect, that risk is minimized as only the saliva will be collected. It can be further reduced if the sample is self-collected under the supervision of a healthcare professional.
A cheap alternative that can help the world in handling the pandemic
Thus far, the only condition with SalivaDirect is that the sample collected should be clear and liquid saliva. This effectively means that the technique cannot be used on hospitalized COVID-19 patients because their saliva samples may contain blood or mucus that can affect the final reading.
Barring this, SalivaDirect does seem to be a good, low-cost, and effective method for rapid detection of COVID-19. The researchers further insisted that they have no intention to commercialize the method. Instead, they want the simplified testing method to help those most in need.
We will get to know soon enough if this technique can be a viable option for widespread testing for COVID-19. So far, it looks promising. If cheap alternatives like SalivaDirect can be implemented across the world it could really help us greatly in handling this pandemic before a proper vaccine arrives.
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