Saliva-based methods for SARS-CoV-2 testing in low- and middle-income countries

Abstract

As the coronavirus disease 2019 (COVID-19) continues to disproportionately affect low- and middle-income countries, the need for simple, accessible and frequent diagnostic testing grows. In lower-resource settings, case detection is often limited by a lack of available testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To address global inequities in testing, alternative sample types could be used to increase access to testing by reducing the associated costs. Saliva is a sensitive, minimally invasive and inexpensive diagnostic sample for SARS-CoV-2 detection that is appropriate for asymptomatic surveillance, symptomatic testing and at-home collection. Saliva testing can lessen two major challenges faced by lower- and middle-income countries: constrained resources and overburdened health workers. Saliva sampling enables convenient self-collection and requires fewer resources than swab-based methods. However, saliva testing for SARS-CoV-2 diagnostics has not been implemented on a large scale in low- and middle-income countries. While numerous studies based in these settings have demonstrated the usefulness of saliva sampling, there has been insufficient attention on optimizing its implementation in practice. We argue that implementation science research is needed to bridge this gap between evidence and practice. Low- and middle-income countries face many barriers as they continue their efforts to provide mass COVID-19 testing in the face of substantial inequities in global access to vaccines. Laboratories should look to replicate successful approaches for sensitive detection of SARS-CoV-2 in saliva, while governments should act to facilitate mass testing by lifting restrictions that limit implementation of saliva-based methods.

Pooled RNA-extraction-free testing of saliva for the detection of SARS-CoV-2

“…Pooling of samples before testing provides a resource-saving approach to increase testing capacity, especially for surveillance in a population with a low infection rate 13 , 15 , such as travellers, school populations and employees of large organisations. Sample pooling also serves communities where the general availability of tests remains limited or cost-prohibitive to the general populace 16 . Even if only testing a certain fraction of the population, these members of the community can serve as a proxy to the broader community, perhaps identifying larger outbreaks through family members and their associated activities.…”

“…However, these dips in regards to COVID-19 cases can lead to a decrease in preventative measures, which inevitably leads to disease resurgence. Additionally, with the ongoing emergence of different SARS-CoV-2 variants of concern, the need for affordable and sustainable mass testing strategies remains, and should be considered necessary throughout all world regions 16 . Our findings suggest that combining saliva with a practical pooling protocol facilitates surveillance testing efforts, especially in resource-limited settings 16 .…”

“…Additionally, with the ongoing emergence of different SARS-CoV-2 variants of concern, the need for affordable and sustainable mass testing strategies remains, and should be considered necessary throughout all world regions 16 . Our findings suggest that combining saliva with a practical pooling protocol facilitates surveillance testing efforts, especially in resource-limited settings 16 . Such pooled testing has the potential to significantly reduce the overall number of tests and associated costs and can likely be more broadly applied to other respiratory pathogens of interest.…”

Exploring the potential of a saliva-based, RNA-extraction-free PCR test for the multiplexed detection of key respiratory pathogens

“…Having demonstrated the potential of saliva to overcome numerous challenges faced during the pandemic for the detection of SARS-CoV-2 (Ott et al, 2021; Vogels et al, 2021) and recognizing its potential for the low-resource discrimination between pathogens(Tan et al, 2022) which produce similar symptom profiles (Laxton et al, 2023), we modified our saliva-based RNA-extraction-free PCR test for SARS-CoV-2 for multiplexed detection of four key respiratory viruses: IAV/IBV, RSV, and hMPV and evaluated its potential application.…”

Saliva-based detection of SARS-CoV-2: a bibliometric analysis of global research

“…However, the collection of both nasopharyngeal and oropharyngeal swabs is uncomfortable for patients and may pose a risk to healthcare workers [ 3 , 4 ]. In addition, the high demand for the materials and reagents needed to sample individuals and the requirement of professional technicians and trained skills to perform RT‒qPCR have resulted in inadequate community-based testing, which might contribute to thousands of preventable COVID-19-related deaths, especially in low- and middle-income countries [ 5 , 6 ]. Thus, alternative specimens that can be conveniently and safely collected and compatible for low-cost point-of-care testing started attracting the attention of researchers in the first half of 2020.…”