From Delta to Omicron SARS-CoV-2 variant: switch to saliva sampling for higher detection rate

ABSTRACT

BackgroundReal-time polymerase chain reaction (RT-PCR) testing on a nasopharyngeal swab is the current standard for SARS-CoV-2 virus detection. Since collection of this sample type is experienced uncomfortable by patients, saliva- and oropharyngeal swab collections should be considered as alternative specimens. ObjectivesEvaluation of the relative performance of oropharyngeal swab, nasopharyngeal swab and saliva for the RT-PCR based SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) variant detection. Study designNasopharyngeal swab, oropharyngeal swab and saliva were collected from 246 adult patients who presented for SARS-CoV-2 testing at the screening centre in Ypres (Belgium). RT-PCR SARS-CoV-2 detection was performed on all three sample types separately. Variant type was determined for each positive patient using whole genome sequencing or Allplex SARS-CoV-2 variants I and II Assay. Results and conclusionsSaliva is superior compared to nasopharyngeal swab for the detection of the Omicron variant. For the detection of the Delta variant, nasopharyngeal swab and saliva can be considered equivalent specimens. Oropharyngeal swab is the least sensitive sample type and shows little added value when collected in addition to a single nasopharyngeal swab. HighlightsO_LISaliva is the preferred sample type for Omicron variant (B.1.1.529) detection C_LIO_LINasopharyngeal swab and saliva are equivalent for Delta variant (B.1.617.2) detection C_LIO_LIOropharyngeal swab is the least preferred sample type for SARS-CoV-2 detection C_LI