Table 1.
Concordance of the QAT with the RT-qPCR in different time periods.
| (A) QAT vs RT-qPCR: all periods | ||||
|---|---|---|---|---|
| RT-qPCR |
||||
| Positive | Negative | Total | ||
| Antigen test | Positive | 66 | 1 | 67 |
| Negative | 14 | 19 | 33 | |
| Positive coincidence rate | 0.82 (0.72–0.90) | |||
| Negative coincidence rate | 0.95 (0.75–0.99) | |||
| Cohen's kappa (SD) | 0.75 (0.62–0.87) | |||
| Gwet's AC1 statistic (SD) | 0.62 (0.45–0.78) | |||
| (B) QAT vs RT-qPCR: from day 1 to day 10 after onset (the early stage) | ||||
| RT-qPCR | ||||
| Positive | Negative | Total | ||
| Antigen test | Positive | 44 | 0 | 44 |
| Negative | 3 | 4 | 7 | |
| Positive coincidence rate | 0.93 (0.82–0.98) | |||
| Negative coincidence rate | 1.00 (0.39–1.00) | |||
| Cohen's kappa (SD) | 0.92 (0.84–1.00) | |||
| Gwet's AC1 statistic (SD) | 0.69 (0.38–1.00) | |||
| (C) QAT vs RT-qPCR: over 10 days after onset (the late stage) | ||||
| RT-qPCR | ||||
| Positive | Negative | Total | ||
| Antigen test | Positive | 22 | 1 | 23 |
| Negative | 11 | 15 | 26 | |
| Positive coincidence rate | 0.66 (0.48–0.82) | |||
| Negative coincidence rate | 0.93 (0.69–0.99) | |||
| Cohen's kappa (SD) | 0.52 (0.27–0.76) | |||
| Gwet's AC1 statistic (SD) | 0.52 (0.30–0.73) | |||
QAT, SARS-CoV-2 quantitative antigen test; RT-qPCR, reverse-transcription quantitative polymerase chain reaction; SD, standard deviation.