Detection of SARS-CoV-2 in the community by nucleic acid amplification testing of saliva

Abstract

Efficient wide-scale testing for SARS-CoV-2 is crucial for monitoring the incidence of the infection in the community. The gold standard for COVID-19 diagnosis is the molecular analysis of epithelial secretions from the upper respiratory system captured by nasopharyngeal (NP) swabs, which requires the intervention of trained personnel. Given the ease of collection, saliva has been proposed as a possible substitute to support testing at the population level. Here we describe the set-up of a laboratory, in an academic context, for the high-throughput screening of SARS-CoV-2 in the saliva from the community. A novel saliva collection device was designed to favour the safe and correct acquisition of the sample as well as the processivity of the downstream molecular analysis. To test the performance of the system,1025 paired saliva and nasopharyngeal samples were collected from individuals recruited at a public drive through testing facility and analysed in parallel. An overall moderate concordance (68%) between the two tests was found, with evidence that neither test can diagnose the infection in 100% of the cases. While the two tests performed equally well in symptomatic individuals, their discordance was mainly restricted to samples from convalescent individuals. The saliva test was at least as effective as NP swabs in asymptomatic individuals recruited for contact tracing. Our study, therefore, indicates that saliva testing can be a reliable tool for wide-scale COVID-19 screening in the community.

SHEAR Saliva Collection Device Augments Sample Properties for Improved Analytical Performance

“…Saliva with high viscosity is challenging for both laboratory-based testing and POC diagnostic applications involving lateral flow assay and paper-based analytical devices. The observed reduction in saliva viscosity, due to the mechanical shearing effects of the SHEAR SCD filter, can ease the pipetting procedures in laboratory-based saliva testing reducing pipetting errors, risk of environmental cross contamination and processing time required (10,11,13). Furthermore, while the viscosity of supernatant after centrifugation was comparable to the viscosity of SHEAR SCD processed saliva, implementation of SHEAR SCD for POC application is more feasible since it does not require additional equipment.…”

“…Viscous matrix is troublesome as it complicates accurate sample processing (e.g. pipetting of accurate volumes) and automation (10)(11)(12)(13)(14). Additionally, salivary mucin networks form complexes with some of the proteins (15), potentially reducing their availability for detection.…”