Prospective comparison of saliva and nasopharyngeal swab sampling for mass screening for COVID-19

Abstract

Current testing for COVID-19 relies on quantitative reverse-transcriptase polymerase chain reaction from a nasopharyngeal swab specimen. Saliva samples have advantages regarding ease and painlessness of collection, which does not require trained staff and may allow self-sampling. We enrolled 776 persons at various field-testing sites and collected nasopharyngeal and pooled saliva samples. 162 had a positive COVID-19 RT-PCR, 61% were mildly symptomatic and 39% asymptomatic. The sensitivity of RT-PCR on saliva samples versus nasopharygeal swabs varied depending on the patient groups considered or on Ct thresholds. There were 10 (6.2%) patients with a positive saliva sample and a negative nasopharyngeal swab, all of whom had Ct values<25. For symptomatic patients for whom the interval between symptoms onset and sampling was <10 days sensitivity was 77% but when excluding persons with isolated Ngen positivity (54/162), sensitivity was 90%. In asymptomatic patients, the sensitivity was only 24%. When we looked at patients with Cts <30, sensitivity was 83% or 88.9% when considering 2 genes. The relatively good performance for patients with low Cts suggests that Saliva testing could be a useful and acceptable tool to identify infectious persons in mass screening contexts, a strategically important task for contact tracing and isolation in the community.

Performance of Saliva, Oropharyngeal Swabs, and Nasal Swabs for SARS-CoV-2 Molecular Detection: a Systematic Review and Meta-analysis

“…While many studies specified self-collected saliva (16, 17, 20, 25-27, 29, 30, 33, 34, 37, 39, 40), some studies described supervised collection (22,28,31,35,38). The % positive saliva was higher for selfcollection than supervised collection although the difference was not substantial [92% (95% CI: 86-96%) vs. 83% (95% CI: 60-98%), respectively, Fig.…”

Saliva as an alternative specimen to nasopharyngeal swabs for COVID-19 diagnosis: Review

“…A large number of studies have been conducted since the COVID-19 pandemic began to determine the efficacy of saliva for COVID-19 diagnosis against the reference standard NPS (). The results from these studies have varied with some finding saliva to be equal to or more sensitive than NPS [38–48] whereas others found it to be less sensitive [49–61]. The specimen collection protocol is one factor that could result in the inconsistencies between these studies ().…”

“…Two studies also noted that whilst saliva sample collection has the potential to be self-administered by the patient in the absence of a trained HCW, it is important that the tube is decontaminated after as it has been noted that patients can spill the sample onto the outside of the tube, which if it contains infectious particles could put individuals processing the sample at risk of infection [47, 61]. Finally, saliva is not a suitable specimen for intubated patients as well as for those who may have difficulty producing saliva due to co-morbidities and/or medications [49, 54, 59].…”

A nanobody-functionalized organic electrochemical transistor for the rapid detection of SARS-CoV-2 and MERS antigens at the physical limit

“…Saliva samples are reported to exhibit comparable or higher viral loads than nasal swaps 43,44 . While this may not lead to perfect sensitivities under real-world sampling conditions 45 , saliva is clearly the better medium for point-of-care or field applications. We, therefore, challenged SARS-CoV nanobody-functionalized OECTs comprising p(g0T2-g6T2) channels with human saliva samples into which we spiked predetermined amounts of target and non-target proteins.…”