A simple pooling salivary test for SARS-CoV-2 diagnosis: A Columbus’ egg?

Abstract

Saliva is an appropriate specimen for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) diagnosis. The possibility of pooling samples of saliva, using non-invasive bibula strips for sampling, was explored employing Bovine coronavirus (BCoV) spiked saliva. In laboratory, up to 30 saliva-soaked strips were pooled in a single tube with 2mL of medium. After quick adsorption with the medium and vortexing, the liquid was collected and tested with a quantitative molecular assay to quantify viral RNA genome copies. On testing of single and pooled strips, the difference between the median Ct value of test performed on the single positive saliva sample and the median threshold cycles (Ct) value obtained on the pool of 30 strips, was 3.21 cycles. Saliva pooling with bibula strips could allow monitoring of COVID-19 on a large scale, reducing costs for the health bodies in terms of medical material and skilled personnel. Finally, saliva sampling is noninvasive and less traumatic than nasopharyngeal swabs and can be self-collected.

Severe acute respiratory syndrome coronavirus 2 detection by real time polymerase chain reaction using pooling strategy of nasal samples

“…This is guaranteed by the high sensitivity of the rRT-PCR which allows to identify even a single positive sample within a pool containing up to 19 negative samples. By performing the test on the 20 pooled samples, the difference between the median Ct value of test performed on the single positive NS and the median Ct value obtained on the 20 samples-pool was 3.11, 3.7, and 4.11 Ct, for E, RdRp and N gene, respectively, thus confirming that pooling strategy is at least as sensitive as testing individual samples ( Pratelli et al, 2021 ). This datum confirms that, even if the pool contains only one low viral load positive sample, the sensibility of the test is not substantially affected.…”

“…Anyhow, NPS collection is time-consuming, uncomfortable, invasive, can generate stress (chiefly for children), requires trained health care personnel and is associated with a no negligible risk of viral transmission ( Azzi et al, 2021 ). These difficulties were addressed and innovative approaches were proposed for simpler and less invasive sampling and for accelerating the screening of groups of people and large populations ( Czumbel et al, 2020 ; Pratelli et al, 2021 ). From the very first months of pandemic onset, growing interest was addressed to the use of self-collected sampling as a suitable first-line screening test for SARS-CoV-2 infection ( Böger et al, 2020 ; Mohammadi et al, 2020 ; Tsang et al, 2021 ), reducing the risk for healthcare workers involved in sampling, and increasing the number of analyses where supplies of personal protection equipment (PPE) are lacking or difficult to find.…”

“…The strategy described in the present note represents the application for the diagnosis of SARS-CoV-2 of the pooling test on bovine coronavirus (BCoV) samples reported by Pratelli et al (2021) . The application of an rRT-PCR test for the diagnosis of SARS-CoV-2 using a pooling strategy with 20 NSs, in order to validate the test for systematic mass monitoring of COVID-19 in companies and in schools, is reported.…”

Pooling of six respiratory samples for the detection of SARS-CoV-2: A validation and cost study in a cohort in Lima, Peru

“…In this study, we observed greater sensitivity values in pooling NS samples than pooling SL samples. This may be due to a lower viral load of SL samples (higher Cts) as compared to NS or NP samples reported in prior studies [ [16] , [17] , [18] ]. Nevertheless, the specificity of both approaches was very high.…”