Direct comparison of clinical diagnostic sensitivity of saliva from buccal swabs versus combined oro-/nasopharyngeal swabs in the detection of SARS-CoV-2 B.1.1.529 Omicron

Abstract

While current guidelines recommend the use of respiratory tract specimens for the direct detection of SARS-CoV-2 infection, saliva has recently been suggested as preferred sample type for the sensitive detection of SARS-CoV-2 B.1.1.529 (Omicron). Here, we compare the clinical diagnostic sensitivity of paired buccal saliva swabs and combined oro-/nasopharyngeal swabs from hospitalized, symptomatic COVID-19 patients collected at median six days after symptom onset by real-time polymerase chain reaction (PCR) and antigen test. Of the tested SARS-CoV-2 positive sample pairs, 55.8% were identified as Omicron BA.1 and 44.2% as Omicron BA.2. Real-time PCR from buccal swabs generated significantly higher quantification cycle (Cq) values compared to those from matched combined oro-/nasopharyngeal swabs and resulted in an increased number of false-negative PCR results. Reduced diagnostic sensitivity of buccal swabs by real-time PCR was observed already at day one after symptom onset. Similarly, detection rates using the Abbott COVID-19 Ag Rapid Test Device were reduced in buccal swabs compared to those using combined oro-/nasopharyngeal swabs. Our results suggest reduced clinical diagnostic sensitivity of saliva from buccal swabs in comparison to combined oro-/nasopharyngeal swabs in the detection of Omicron in symptomatic individuals.