TABLE 1.
Initial and confirmatory LoDs for the Abbott BinaxNOW COVID-19 Ag cardb
| Sample | Dilution | No. of initial replicates detected/no. tested | No. of confirmatory replicates detected/no. tested | Initial % positive | Confirmatory % positive | No. of copies/ml (ddPCR) | No. of copies/swab (ddPCR) | No. of copies/ml (cobas) | No. of copies/swab (cobas) |
|---|---|---|---|---|---|---|---|---|---|
| S0a | Neat | 3/3 | 100 | 5.65 × 107 | 2.83 × 106 | 1.13 × 108 | 5.64 × 106 | ||
| S1 | 1:10 | 3/3 | 100 | 5.65 × 106 | 2.83 × 105 | 1.13 × 107 | 5.64 × 105 | ||
| S1-2 | 1:20 | 3/3 | 100 | 2.83 × 106 | 1.42 × 105 | 5.64 × 106 | 2.82 × 105 | ||
| S1-4 | 1:40 | 3/3 | 100 | 1.41 × 106 | 7.05 × 104 | 2.82 × 106 | 1.41 × 105 | ||
| S1-5 | 1:50 | 3/3 | 100 | 1.13 × 106 | 5.65 × 104 | 2.26 × 106 | 1.13 × 105 | ||
| S1-6 | 1:60 | 3/3 | 100 | 9.42 × 105 | 4.71 × 104 | 1.88 × 106 | 9.40 × 104 | ||
| S1-7 | 1:70 | 3/3 | 20/20 | 100 | 100 | 8.07 × 105 | 4.04 × 104 | 1.61 × 106 | 8.06 × 104 |
| S1-8 | 1:80 | 3/3 | 17/20 | 67 | 85 | 7.06 × 105 | 3.53 × 104 | 1.41 × 106 | 7.05 × 104 |
| S2 | 1:100 | 0/3 | 0 | 5.65 × 105 | 2.83 × 104 | 1.13 × 106 | 5.64 × 104 | ||
| S3 | 1:1,000 | 0/3 | 0 | 5.65 × 104 | 2.83 × 103 | 1.13 × 105 | 5.64 × 103 | ||
| Positive control | Neat | 1/1 | 1/1 | 100 | 100 | NA | NA | NA | NA |
| Negative control | Neat | 0/1 | 0/1 | 0 | 0 | NA | NA | NA | NA |
a
S0, the undiluted positive pool, was determined to have a CT of 17.3 for both targets on the Roche cobas 6800 platform.
b
The positive control was a kit-provided swab by Abbott; the negative control was a clinical nasopharyngeal swab previously determined to be negative by Hologic Panther Fusion. Abbreviations: ddPCR, droplet digital PCR; Pos, positive; Neg, negative; NA, not applicable. The two dilutions that confirm the LoD are in boldface.