Table 4.
The effect of symptoms onset time and Ct values on the diagnostic performance.
| No. | Model | N | Prevalence | Sensitivity | Specificity | Negative predicted value | Positive predicted value | Kappa (p <0.001) |
|---|---|---|---|---|---|---|---|---|
| 1 | Symptom onset within 7 days | 1,290 | 20% (18–22.8%) |
82.6% (77.5–87%) |
99.3% (98.6–99.7%) |
95.7% (94.3–96.8%) |
96.9% (93.7–98.7%) |
86.6% (83.1–90.1%) |
| 2 | Symptom onset within 5 days | 1,252 | 20% (18–22.8%) |
82.4% (77.2–86.9%) |
99.3% (98.6–99.7%) |
95.6% (94.2–96.8%) |
96.8% (93.5–98.7%) |
86.5% (82.9–90.1%) |
| 3 | Excluding cases with Ct ≥ 30 | 4,148 | 17% (16–18.1%) |
84.5% (81.6–87.1%) |
99.1% (98.8–99.4%) |
96.9% (96.3–97.5%) |
95.2% (93.2–96.7%) |
87.5% (85.5–89.6%) |
| 4 | Excluding cases with Ct > 24 | 3,996 | 14% (13–15%) |
87.9% (84.9–90.5%) |
99.1% (98.8–99.4%) |
98.1% (97.6–98.5%) |
94.2% (91.8–96.1%) |
89.5% (87.5–91.6%) |
| 5 | Symptom onset within 7 days and Excluding cases with Ct ≥ 30 | 1,274 | 20% (17–21.8%) |
86.3% (81.4–90.4%) |
99.3% (98.6–99.7%) |
96.8% (95.5–97.8%) |
96.8% (93.6–98.7%) |
89.3% (86.1–92.5%) |
| 6 | Symptom onset within 7 days and Excluding cases with Ct > 24 | 1,220 | 16% (14–18.3%) |
89.3% (84.2–93.3%) |
99.3% (98.6– 99.7%) |
98% (96.9–98.7%) |
96.2% (92.3–98.4%) |
91.3% (88.1–94.5%) |
| 7 | Symptom onset within 5 days and Excluding cases with Ct > 30 | 1,236 | 19% (17–21.8%) |
86.3% (81.3–90.4%) |
99.3% (98.6–99.7%) |
96.8% (95.5–97.8%) |
96.7% (93.4–98.7%) |
89.3% (86.0–92.5%) |
| 8 | Symptom onset within 5 days and Excluding cases with Ct > 24 | 1,184 | 16% (14–18.3%) |
89.5% (84.2–93.5%) |
99.3% (98.6–99.7%) |
98% (96.9–98.8%) |
96% (92–98.4%) |
91.3% (88.1–94.5%) |