Table 1. Five clinical samples collected at the Cadham Provincial Laboratory (CPL) were selected for analysis with Ct values ranging from 23–35 as determined by the CPL in-house RT-qPCR test.
| Sample ID | RT-qPCR Ct Value | Nominal Viral Load (cp/mL) | Undiluted | Three Sample Pool | Six Sample Pool (Replicate 1) | Six Sample Pool (Replicate 2) | Six Sample Pool (Replicate 3) | Replicate Standard Dev. | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| E | N2 | SPC | E | N2 | SPC | E | N2 | SPC | E | N2 | SPC | E | N2 | SPC | E | N2 | SPC | |||
| CPL1 | 23 | 2,452,553 | 22.2 | 24.7 | 29.2 | 22.8 | 24.3 | 24.3 | 24.3 | 26.2 | 27.3 | 23.8 | 25.8 | 27.6 | 24.3 | 26.5 | 27.3 | 0.21 | 0.29 | 0.14 |
| CPL2 | 26 | 154,663 | 26.1 | 28.9 | 28.7 | 27.1 | 28.0 | 28.0 | 28.0 | 30.6 | 27.8 | 28.2 | 30.9 | 28.1 | 28.0 | 30.8 | 27.7 | 0.09 | 0.12 | 0.17 |
| CPL3 | 31 | 6439 | 30.5 | 33.9 | 28.4 | 31.9 | 33.5 | 33.5 | 33.5 | 37.4 | 28.1 | 34.1 | 36.7 | 27.9 | 33.5 | 36.6 | 28.2 | 0.37 | 0.36 | 0.12 |
| CPL4 | 33 | 2245 | 32.0 | 35.5 | 28.6 | 33.3 | 35.6 | 35.6 | 35.6 | 37.7 | 27.4 | 33.0 | 36.1 | 27.7 | 35.6 | 38.7 | 27.7 | 1.07 | 1.07 | 0.14 |
| CPL5 | 35 | 938 | 33.6 | 36.3 | 28.0 | 36.2 | 40.7 | 40.7 | 40.7 | 41.1 | 27.6 | 39.0 | 39.2 | 27.6 | 40.7 | 39.1 | 27.7 | 1.77 | 0.92 | 0.05 |
Each sample was tested with the Xpert® Xpress SARS-CoV-2 assay as an undiluted sample, or diluted three or six-fold in negative clinical samples to simulate a three or six (performed in triplicate) sample pool. Ct values are provided for the envelope (E), nucleocapsid (N), and sample processing control (SPC) targets at each dilution. Nominal viral load of the clinical samples was determined using a standard curve of the Xpert® Xpress SARS-CoV-2 assay. For the six sample pool replicates, standard deviation was calculated for each target.