Self-collected oral fluid saliva is insensitive compared to nasal-oropharyngeal swabs in the detection of SARS-CoV-2 in outpatients

Manabe, Yukari C; Reuland, Carolyn; Yu, Tong; Azamfirei, Razvan; Hardick, Justin P; Church, Taylor; Brown, Diane M; Sewell, Thelio T; Antar, Annuka; Blair, Paul W; Heaney, Chris D; Pekosz, Andrew; Thomas, David L

SARS-CoV-2 pandemic control will require widespread access to accurate diagnostics. Salivary sampling circumvents swab supply chain bottlenecks, is amenable to self-collection, and is less likely to create an aerosol during collection compared to the nasopharyngeal swab. We compared rRT-PCR Abbott m2000 results from matched salivary oral fluid (gingival crevicular fluid collected in an Oracol device) and nasal-oropharyngeal (OP) self-collected specimens in viral transport media from a non-hospitalized, ambulatory cohort of COVID-19 patients at multiple time points. There were 171 matched specimen pairs. Compared to nasal-OP swabs, 41.6% of the oral fluid samples were positive. Adding spit to the oral fluid collection device increased the percent positive agreement from 37.2% (16/43) to 44.6% (29/65). The percent positive agreement was highest in the first 5 days after symptoms and decreased thereafter. All of the infectious nasal-OP samples (culture positive on VeroE6 TMPRSS2 cells) had a matched SARS-CoV-2 positive oral fluid sample. In this study of non-hospitalized SARS-CoV-2 infected persons, we demonstrate lower diagnostic sensitivity of self-collected oral fluid compared to nasal-OP specimens, a difference that was especially prominent more than 5 days from symptom onset. These data do not justify the routine use of oral fluid collection for diagnosis of SARS-CoV-2 despite the greater ease of collection. It also underscores the importance of considering the method of saliva specimen collection, and the time from symptom onset especially in outpatient populations.