The Application of Sample Pooling for Mass Screening of SARS-CoV-2 in an Outbreak of COVID-19 in Vietnam

Abstract

We sampled nasal–pharyngeal throat swabs from 96,123 asymptomatic individuals at risk of SARS-CoV-2 infection, and generated 22,290 pools at collection, each containing samples from two to seven individuals. We detected SARS-CoV-2 in 24 pools, and confirmed the infection in 32 individuals after resampling and testing of 104 samples from positive pools. We completed the testing within 14 days. We would have required 64 days to complete the screening for the same number of individuals if we had based our testing strategy on individual testing. There was no difference in cycle threshold (Ct) values of pooled and individual samples. Thus, compared with individual sample testing, our approach did not compromise PCR sensitivity, but saved 77% of the resources. The present strategy might be applicable in settings, where there are shortages of reagents and the disease prevalence is low, but the demand for testing is high.

Feasibility and efficacy of mass testing for SARS-CoV-2 in a UK university using swab pooling and PCR

“…4b), and no differences in the distributions of CT values were observed between paired tests stratified by number of swabs (Fig 4c). Taken together, and in agreement with previous studies [46][47][48] , these data strongly argue that swab pooling does not result in any significant loss of PCR test sensitivity.…”

“…This method requires additional sample manipulation, and results in dilution of viral RNA present in individual samples. Alternatively, tests may be pooled at the time swabs (samples) are taken, by combining multiple swabs from individuals in the same sample tube (swab pooling, also known as cohort pooling, or pooling at source) [46][47][48] . This approach avoids reductions in test sensitivity caused by sample dilution, and disruption of existing laboratory workflows.…”

Phylodynamic analysis of SARS-CoV-2 spread in Rio de Janeiro, Brazil, highlights how metropolitan areas act as dispersal hubs for new variants

“…Therefore, identification and surveillance of these hubs are of fundamental value to early control new variants that may emerge in the future. The results also suggest that non-medical interventions such as mass screening (37)(38)(39)(40), use of masks (41)(42)(43), social distancing and lockdowns (44)(45)(46) in metropolitan areas might result in better long-term effects on pandemic control than when applied on small cities, because it may reduce the number of seeding events on small cities (47)(48)(49).…”

Proactive response and innovative approaches to SARS-CoV-2 in Vietnam

“…On 5 March, the first locally produced COVID-19 RT-PCR test kit developed by Military Medical University was The availability of in-country capacity has allowed Vietnam to integrate mass PCR screening into its national COVID-19 control programme. For example, during the Da Nang outbreak in July-August, mass screening coupled with an innovative sample pooling strategy 11 was applied. Accordingly, swabs from two to seven individuals living in areas under lockdown were placed in one tube at collection for mass screening (figure 3).…”

“…Figure3Illustration of the sample pooling strategy that was successfully applied for mass screening of SARS-CoV-2 during the second wave of COVID-19 in Vietnam, July-August 2020 11. Nasal-pharyngeal throat swabs from two to seven individuals were combined in a single 15 mL collection tube containing 3 mL of viral transport medium for subsequent reverse transcription (RT)-PCR screening for SARS-CoV-2.…”