Saliva Testing for Diagnosing COVID-19

For diagnosing COVID-19, saliva sampling has two big advantages over nasopharyngeal (NP) swabbing: It is far less uncomfortable for patients, and it eliminates risky exposures for healthcare personnel who are collecting specimens. Small studies have suggested saliva tests have acceptable performance characteristics; now, larger studies are becoming available.

Yale researchers used a proprietary protocol to process saliva specimens from two high-prevalence populations. Among 70 inpatients with COVID-19 that was diagnosed by standard nasopharyngeal swabbing, sequential testing of self-collected saliva specimens performed similarly to repeat swab testing during hospitalization; in fact, saliva testing was somewhat less variable in quantitating RNA than were swabs. The authors also screened 495 asymptomatic healthcare workers with occupational COVID-19 exposures: 13 participants' saliva specimens tested positive for SARS-CoV-2. Of the 9 participants who also collected their own NP swabs, only 2 had positive swab tests. All 13 asymptomatic patients with positive saliva tests subsequently had COVID-19 confirmed by additional NP swabs.

Researchers in Canada used a different proprietary kit to analyze almost 2000 paired self-collected saliva and standard swab specimens obtained from asymptomatic or mildly symptomatic individuals with high clinical suspicion of COVID-19. Overall, 70 patients had positive tests: 34 were positive by both saliva and swab, 22 by swab alone, and 14 by saliva alone. Repeat sampling was not performed.