Assessing PCR Compatibility of Swab Types

Although all of the above swabs are routinely used for PCR testing, as a double-check, each swab type was assessed for PCR compatibility by overnight incubation in 3 ml of modified CDC VTM (allowing potential PCR inhibitors time to leech into media), spiking 1.5 ml of medium with 200 copies/ml of control SARS-CoV-2 amplicon target (twice the LoD of our system), vortexing, and testing using the Abbott RealTime SARS-CoV-2 assay on an Abbott m2000 RealTime system platform (18 ), the assay and platform used for all testing in this report, following the same protocol used for clinical testing (see below). All swabs examined in this study passed this quality-control testing for lack of RT-PCR inhibition based on observation of cycle threshold (C_T) values within expected quality control limits (17 (link)).