Development and Validation of a Lateral Flow Immuno-Assay to Diagnose Covid-19 in Saliva (DAVINCI)
The DAVINCI consortium developed and validated a test, suitable for home use, that uses saliva samples to identify the presence of SARS-CoV-2 antigens and antibodies. The test can therefore simultaneously inform the user whether they are currently infected with the COVID-19 virus and whether they have had prior exposure to the virus. A smartphone app was also developed to support the test user.
The Need for Antibody Tests to Provide Information about COVID-19 Exposure
Following the identification of the COVID-19 causing SARS-CoV-2 virus, diagnostic tests were made quickly available. These tests were crucial for detecting active infections and therefore enabling targeted management of virus spread. However, there was also an urgent need for tests which could identify the presence of COVID-19-specific antibodies and thereby provide information about the degree of COVID-19 exposure within the population so far. This information was crucial for accurately informing public health organisations about the extent of the outbreak, and helping scientists to answer basic questions, such as:
- How many people have been infected with the virus?
- Who may have spread it without knowing?
- How deadly is COVID-19?
- What measures are needed to slow its spread?
Antibody tests most commonly use a blood sampling method. However, this consortium, led by Prof Daniel Paris recognised that there would be significant value in developing a test which identifies the presence of COVID-19 antibodies in saliva. Saliva is often referred to as a ‘mirror of the body.’ Like blood, saliva contains proteins, DNA and RNA that can be assessed for abnormalities and diseases. Unlike blood-based tests, it is easy for people to carry out saliva-based tests in their own homes.
A New Saliva-Based Test to Identify Antigens and Antibodies
The consortium developed and validated a test, suitable for home use, that uses saliva samples to identify the presence of SARS-CoV-2 antigens (indicating current infection) and antibodies (indicating prior exposure to the virus and potentially a degree of immunity). The use of the test requires that the user spits into a device funnel. After 12 minutes, the device displays the result as test lines similar to those displayed on a pregnancy test.
In addition, the consortium developed an app for iOS and Android that takes a step-by-step approach to guiding the user through the sampling and measurement processes. A key feature of the app is that it can evaluate and interpret the test results from a picture of the device after test completion. Using bespoke image recognition code, the app identifies unique window and casing markers and uses these to orient the images and locate the test and control lines. The code subsequently analyses the test lines and ultimately determines the result of the test. The app also allows for user registration and storage of past results, enabling the user to track results over time.
A Wide Range of Potential Applications for the Test
The device developed in the DAVINCI project was the first testing platform which uses only saliva and no additional reagents. It does not require additional specialist equipment or personnel and therefore has a wide range of potential uses, for example in low- and middle-income countries, in people’s homes and for the testing of large groups of people, such as at events. Beyond COVID-19 it holds promise for a range of other diseases for which antibodies and antigens can be identified using saliva samples, for example, dengue virus and influenza.
Banner illustration above: Credit: DAVINCI.
