Fig. 2: Validation in clinical specimens demonstrates a limit of detection that is equivalent to sensitive RT–qPCR reactions.
a, Limit of detection in nasal swab samples with no SARS-CoV-2 that were pooled and then ATCC inactivated virus was added at different concentrations. Nasal swab samples were RNA-purified and tested using SwabSeq, showing a limit of detection of 250 GCE per ml. b, RNA-purified clinical nasal swab specimens obtained through the UCLA Health Clinical Microbiology Laboratory were tested on the basis of clinical protocols using FDA-authorized systems and then also tested using SwabSeq. This represents a subset of the total purified RNA samples used in our validation. We show 100% agreement with samples that tested positive for SARS-CoV-2 (n = 63) and negative for SARS-CoV-2 (n = 159). c, We also tested RNA-purified samples from extraction-free nasopharyngeal swabs and showed a limit of detection of 558 GCE per ml. d, The relationship between Ct from RT–qPCR targeting the S gene (x axis) and the SwabSeq ratio for extraction-free swabs in normal saline or TE buffer (y axis) for patient samples classified as testing positive or negative for SARS-CoV-2 by the UCLA Clinical Microbiology Laboratory. Samples with no virus detected were assigned a Ct value of 0 for this visualization. e, Extraction-free processing of saliva specimens shows a limit of detection down to 1,000 GCE per ml. f, Extraction-free processing of saliva clinical specimens using SwabSeq (y axis) compared to classification of SARS-CoV-2 status from RNA-purified clinical nasal swab specimens for matched samples (x axis).
