An additional three clinical specimens with high Ct values were selected to observe the effect of sample pooling close to the limit of detection of the Xpert® Xpress SARS-CoV-2 assay.

This included two samples provided by the National Microbiology Laboratory and one from the Cadham Provincial Laboratory (CPL), which is a discordant sample not detected by CPL’s Corman RT-qPCR test, but detected as a weak positive by the Xpert® assay. At the six-fold dilution, the weak positive was no longer detected by the assay.