Table 1.
Ct Changes of the Xpert Xpress SARS-CoV-2 Target Genes Following 10:1 Pooling
| E Gene | N2 Gene | |||||
|---|---|---|---|---|---|---|
| Specimen | Original Ct | 10:1 Pool Ct | Ct Difference | Original Ct | 10:1 Pool Ct | Ct Difference |
| Midrangea | ||||||
| 1 | 29.8 | 32.7 | 2.9 | 32.8 | 36.3 | 3.5 |
| 2 | 31.4 | 36.1 | 4.7 | ND | ND | NA |
| 3 | 33.1 | ND | NA | 35.4 | 40.4 | 5.0 |
| 4 | 32.8 | 39.6 | 6.8 | 35.5 | 40.5 | 5.0 |
| 5 | 30.5 | ND | NA | 33.9 | 43.2 | 9.3 |
| 6 | 30.7 | 37.3 | 6.6 | 34.7 | 38.5 | 3.8 |
| 7 | 30.0 | 33.3 | 3.3 | 32.8 | 36.9 | 4.1 |
| 8 | 32.4 | ND | NA | 35.4 | 39.2 | 3.8 |
| 9 | 30.1 | 33.5 | 3.4 | 33.2 | 37.1 | 3.9 |
| 10 | 33.0 | ND | NA | 36.2 | 39.6 | 3.4 |
| Late rangeb | ||||||
| 11 | 41.5 | ND | NA | 39.5 | 41.8 | 2.3 |
| 12 | 35.2 | ND | NA | 39.0 | ND | NA |
| 13 | ND | ND | NA | 41.7 | 43.0 | 1.3 |
| 14 | ND | ND | NA | 43.0 | ND | NA |
| 15 | 35.8 | 38.3 | 2.5 | 36.4 | 41.3 | 4.9 |
| 16 | ND | ND | NA | 39.1 | 41.1 | 2.0 |
| 17 | 40.3 | ND | NA | 41.0 | ND | NA |
| 18 | 35.0 | 41.8 | 6.8 | 38.0 | 39.5 | 1.5 |
| 19 | 42.3 | 41.8 | −0.5 | 38.6 | 40.5 | 1.9 |
| 20 | 38.3 | ND | NA | 38.9 | 41.7 | 2.8 |
Ct, crossing threshold; NA; not available; ND, not detected; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
aMidrange: 25-34 cycles.
bLate range: >34-45 cycles.