Table 2. Diagnostic accuracy of COVID-19 RT-PCR on saliva samples relative to nasopharyngeal samples considering different patient groups and Ct thresholds.
| Sensitivity (95% CI) | Specificity (95% CI) | Positive predictive value (95% CI) | Negative predictive value (95% CI) | Cohen’s Kappa | |
|---|---|---|---|---|---|
| Asymptomatic, any gene, any Ct, any delay (N = 90 positives) | 16.8 (10.1–25.6) | 98.9 (97.7–99.6) | 73.9 (51.6–89.8) | 87.2 (84.4–89.7) | 0.23 |
| Any gene, any Ct any delay (N = 223 positives) | 45.4 (38.6–52.5) | 98.7 (97–98.9) | 86.2 (78.3–92.1) | 87.6 (85.3–89.7) | 0.52 |
| Symptoms <10 days (N = 94 positives) | 72.7 (62.2–81.7) | 96.9 (93.3–98.8) | 91.4 (82.3–97.8) | 88.6 (83.5–92.6) | 0.73 |
| Symptoms <10 days & at least 2 positive target genes (N = 79 positives) | 78.1 (66.9–86.9) | 96.9 (93.3–98.9) | 90.5 (89.4–96.4) | 92.1 (87.5–95.4) | 0.78 |
| 2 positive target genes with Ct<35 (N = 84 positives) | 100 (95.6–100) | 99.9 (99.4–100) | 98.8 (93.5–99.9) | 100 (99.6–100) | 0.98 |