Mass screening of asymptomatic persons for SARS-CoV-2 using saliva

Abstract

Background COVID-19 has rapidly evolved to become a global pandemic due largely to the transmission of its causative virus through asymptomatic carriers. Detection of SARS-CoV-2 in asymptomatic people is an urgent priority for the prevention and containment of disease outbreaks in communities. However, few data are available in asymptomatic persons regarding the accuracy of PCR testing. Additionally, although self-collected saliva has significant logistical advantages in mass screening, its utility as an alternative specimen in asymptomatic persons is yet to be determined. Methods We conducted a mass-screening study to compare the utility of nucleic acid amplification, such as reverse transcriptase polymerase chain reaction (RT-PCR) testing, using NPS and saliva samples from each individual in two cohorts of asymptomatic persons: the contact tracing cohort and the airport quarantine cohort. Results In this mass-screening study including 1,924 individuals, the sensitivity of nucleic acid amplification testing with nasopharyngeal and saliva specimens were 86% (90%CI:77-93%) and 92% (90%CI:83-97%), respectively, with specificities greater than 99.9%. The true concordance probability between the nasopharyngeal and saliva tests was estimated at 0.998 (90%CI:0.996-0.999) on the estimated airport prevalence, 0.3%. In positive individuals, viral load was highly correlated between NPS and saliva. Conclusion Both nasopharyngeal and saliva specimens had high sensitivity and specificity. Self-collected saliva is a valuable specimen to detect SARS-CoV-2 in mass screening of asymptomatic persons.

Relative Sensitivity of Saliva and Upper Airway Swabs for Initial Detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Ambulatory Patients

“…In one cohort, supervised saliva collection was more sensitive than URS swab, and unsupervised saliva collection was less sensitive). 25 In the remaining cohorts, saliva samples demonstrated lower sensitivity than URS swabs in comparison with the CRS. However, most studies demonstrated wide overlap in the confidence intervals for saliva and URS specimens.…”

“…One hundred forty-nine papers were considered for inclusion; of these, 19 studies comprising 21 cohorts met inclusion criteria ( Supplemental Figure S1 ). A brief summary of the studies included in this review may be found in Table 1 , and a brief discussion of each paper (including the results used in this review) is presented in the Supplemental Appendix S1 3 , 4 , 5 , 6 , 7 , 8 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 . Twelve of the included cohorts involved 100 or more patients.…”

“…Twelve of the included cohorts involved 100 or more patients. Two of the studies separately presented data for two cohorts; one study presented data for a single cohort in which two approaches were used to collect saliva specimens 25 .…”

“…Importantly, 5 of the 7 cohorts in which saliva provided greater sensitivity were thought to be associated with a high risk of spectrum bias with respect to initial diagnostic testing of a community population 21 , 22 , 25 , 27 , 29 . Of 10 cohorts that included patients who had previously tested positive for SARS-CoV2, or included hospitalized patients, four showed higher sensitivity for saliva specimens 21 , 25 , 27 , 29 , two showed sensitivity identical to that for NP swabs 23 , 28 , and four showed higher sensitivity for NP or MT swabs 17 , 18 , 20 , 26 . A single study of asymptomatic health care workers identified four positives from saliva samples and none using NP swabs 22 .…”

“…Equivocal results and assay failures were not used in the calculation of sensitivity, nor in the construction of the CRS for each study. Confidence limits for sensitivity were computed using Newcombe’s efficient score method 16 as implemented in the Vassarstats Clinical Calculator 1 ( http://vassarstats.net/ )( Table 1 ) 3 , 4 , 5 , 6 , 7 , 8 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 . Criteria for performing a formal meta-analysis were as follows: 1) studies used the same amplification technology [such as RT-PCR]; 2) studies used the same upper airway sample site (AN, MT and NP could be included together, but not admixed with studies based on OP samples; 3) studies enrolled a similar patient mix (e.g., symptomatic, asymptomatic, hospitalized) and similar clinical environment (drive-through/ community health center or hospital).…”