An innovation based on progress in molecular biology
The idea took root in the mind of Vincent Thibault in 2018.
This professor at the University of Rennes, head of the virology laboratory of the University Hospital (CHU) and researcher at the Research Institute for Environmental and Occupational Health, IRSET, is also an admirer of the feats of forensic experts.
If today’s investigators can detect DNA fragments on samples that are several years old, why wouldn’t it be possible to detect the genomes of respiratory viruses on used tissues, just several days old?
This technique can be envisaged thanks to significant progress in automated analysis used in molecular biology, now common in medical laboratories, such as the one led by Professor Thibault at the University Hospital (CHU) of Rennes.
To test the reliability of this method, the researcher mobilised a team of investigators that followed two complementary approaches.
A method tested in a group situation...
The team began by experimenting with a collective approach, using tissues collected each week in the crèche of the University Hospital (CHU) of Rennes and in primary schools over long periods (one year for the crèche).
For ethical reasons, each weekly analysis was performed once on all the tissues of an entire class or a section of the crèche. This technique, known as ‘pooling’, makes it possible to detect the presence of a virus in a group, without being able to trace it back to a particular individual.
The result: the comprehensive monitoring, on a week-by-week basis, of the circulation of the main respiratory viruses among children, with the added bonus of very early detection of the flu pandemic, as the virus appeared in this crèche six weeks before the 2019 peak was reached in metropolitan France.
...and then individually
Given the success of this collective approach, the team recruited over 50 volunteers with various respiratory symptoms, to test detection sensitivity, this time on an individual basis. Out of the 50 tissues analysed, only two tested negative.
The reliability of the method was also tested on a subgroup of 15 volunteers with SARS-CoV-2, the virus responsible for COVID-19. Each of the subjects tested positive with the standard method: nasal swab followed by RT-PCR analysis. On the same day, these same subjects provided a used tissue, tested using the new method.
All the tissues revealed SARS-CoV-2, and in two-thirds of these the detection was more clear-cut than with the RT-PCR test (less diagnostic machine cycles were required to detect the viral genome signal).
So, does this mean an end to nasal swabs?
In some cases, the tissues were sent by mail and kept somewhere from several days to six months at room temperature. In all cases, the viral genome remained detectable.
These very promising results, based on major progress in automated molecular biology analysis, remain to be confirmed by other studies that will be performed on larger populations.
Already, other teams have published results that confirm the overall feasibility of this approach (successful detection of viruses on old single-use antigen test cassettes for example).
This method has its limitations however. The person must be able to blow their nose correctly, and there is more laboratory work involved such as extraction, which is normally done at home in the case of nasal swabs.
In the near future, one could imagine the simplified screening of viral respiratory infections. If the results of the study are confirmed, it will be possible for patients to blow their nose, place the tissue in the bag provided and send or bring it to a laboratory for analysis, with the same reliability as the nasal swab.
All this without the disadvantages of a method considered unpleasant, especially for children.
Using Discarded Facial Tissues to Monitor and Diagnose Viral Respiratory Infections
Gisele Lagathu, Claire Grolhier, Juliette Besombes, Anne Maillard, Pauline Comacle, Charlotte Pronier, Vincent Thibault
Emerg Infect Dis. 2023;29(3):511-518 | doi:10.3201/eid2903.221416
Other references demonstrating the possibility of detecting viral genomes on used antigen tests, even after several months of storage:
Nazario-Toole A et al.
Sequencing SARS-CoV-2 from antigen tests
PLOS ONE. févr 2022;17(2):e0263794.
Macori G et al.
Inactivation and Recovery of High Quality RNA From Positive SARS-CoV-2 Rapid Antigen Tests Suitable for Whole Virus Genome Sequencing
Frontiers in Public Health. 2022;10.
Martin GE et al. [8 days – real life, self-collected device: 42+/65]
Maintaining genomic surveillance using whole-genome sequencing of SARS-CoV-2 from rapid antigen test devices.
The Lancet Infectious Diseases. 1 oct 2022;22(10):1417 8.
Rector A et al.
Sequencing directly from antigen-detection rapid diagnostic tests in Belgium, 2022: a gamechanger in genomic surveillance? Eurosurveillance. 2 mars 2023;28(9):2200618.