top of page

Saliva-based COVID-19 tests display high accuracy with and without symptoms

A clinical evaluation of a simplified processing method for a rapid COVID-19 test has shown high accuracy in people with and without symptoms.

Saliva and swab-based RT-LAMP tests are more scalable than standard COVID-19 PCR tests. Their faster results are possible because several changes of temperature are not needed.

The tests are currently used in a widespread saliva testing programme across Hampshire and the Isle of Wight.

A research team including Southampton scientists have published findings from their multi-site evaluation in the Journal of Molecular Diagnostics.

Scalable alternative to PCR tests

Loop-mediated isothermal amplification (LAMP) is a single-tube technique for the amplification of DNA. Reverse Transcription LAMP (RT-LAMP) combines LAMP with an extra step to allow the detection of genetic material known as RNA.

This latest trial by NHS Trusts and universities tested samples from saliva and swabs. These were analysed both directly (Direct RT-LAMP) on the sample and after extraction of the viral RNA (RNA RT-LAMP).

For RNA RT-LAMP on swabs, the overall diagnostic sensitivity was as high as RT-qPCR testing. This supports the use of such testing in mobile testing units, as recently seen for overseas visitors to high level meetings in the UK.

Dr Veronica Fowler, a virologist who pioneered the optimisation and validation of the RT-LAMP technology for COVID-testing, said:

“The application of using lower cost, rapid molecular tests, such as RT-LAMP to identify and control highly infectious viral diseases has been performed in the veterinary world for years. I am pleased through this huge collaborative effort that we have succeeded in transferring this concept and practice within the human infectious disease world for the benefit of saving people’s lives.”

Accurate tests in cases without symptoms

During the clinical trial, direct RT-LAMP was performed on 559 swabs and 86,760 saliva samples. RNA RT-LAMP was performed on 12,619 swabs and 12,521 saliva samples from asymptomatic and symptomatic people across healthcare and community settings.

For Direct RT-LAMP, the overall diagnostic sensitivity was highest (85%) on saliva samples, with a specificity of 100% when compared to standard RT-qPCR testing. In tests on saliva samples containing a high viral load, the sensitivity of the test increased to 99%. This indicates that the test is highly effective in identifying infectious cases, including from people not displaying symptoms.

The findings demonstrate that RT-LAMP can be applied to a variety of use-cases. These include regular testing of saliva from people without symptoms that could be missed using symptomatic testing alone.

Prof Keith Godfrey, of the NIHR Southampton Biomedical Research Centre, who led the community-based aspects of the evaluation, said:

“It is extremely helpful to have the ‘real world’ demonstration of how the RT-LAMP test can be implemented in different settings. It provides an important example of how these tests can make a valuable contribution to overall COVID-19 testing capability.

“The saliva-based RT-LAMP test has proven easy to use, effective and highly acceptable to people of all ages for regular testing. Research in Southampton has shown that such testing can play a valuable role in controlling COVID-19 transmission in educational settings.”

bottom of page