Table 3.
CT diagnostic accuracy
| Highly suggestive CT findings | ||||||||
| TP | FP | TN | FN |
Sensitivity (95% CI) |
Specificity (95% CI) |
PPV (95% CI) |
NPV (95% CI) |
|
|
Reference standard 1 Prevalence 79.2% |
423 | 31 | 114 | 128 |
76.77% (73.0–80.2%) |
78.62% (71.0–85.0%) |
93.17% (90.4–95.3%) |
47.11% (40.7–53.6%) |
|
Reference standard 2 Prevalence 80.9% |
428 | 26 | 107 | 135 |
76.02% (72.3–79.5%) |
80.45% (72.7–86.8%) |
94.27% (91.7–96.2%) |
44.21% (37.9–50.7%) |
|
Reference standard 3 Prevalence 85.6% |
438 | 16 | 84 | 158 |
73.49% (69.8–77.0%) |
84.00% (75.3–90.6%) |
96.48% (94.3–98.0%) |
34.71% (28.7–41.1%) |
| Highly suggestive + suggestive CT findings | ||||||||
| TP | FP | TN | FN |
Sensitivity (95% CI) |
Specificity (95% CI) |
PPV (95% CI) |
NPV (95% CI) |
|
|
Reference standard 1 Prevalence 79.2% |
520 | 61 | 84 | 31 |
94.37% (92.1–96.1%) |
57.93% (49.5–66.1%) |
89.50% (86.7–91.9%) |
73.04% (64.0–80.9%) |
|
Reference standard 2 Prevalence 80.9% |
526 | 55 | 78 | 37 |
93.43% (91.1–95.3%) |
58.65% (49.8–67.1%) |
90.53% (87.9–92.8%) |
67.83% (58.5–76.2%) |
|
Reference standard 3 Prevalence 85.6% |
539 | 42 | 58 | 57 |
90.44% (87.8–92.7%) |
58.0% (47.7–67.8%) |
92.77% (90.4–94.7%) |
50.43% (41.0–59.9%) |
Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) with respective 95% confidence intervals (CI) for two levels of CT-based probability of COVID-19 pneumonia (highly suggestive only and highly suggestive plus suggestive findings), and for three reference standards: (1) the first RT-PCR; (2) plus repeated RT-PCR tests (within 15 days) in patients with negative first RT-PCR; if RT-PCR was not repeated the patient was considered negative; (3) as in the second scenario, but negative patients who were not retested with RT-PCR were classified as positive or negative in the same proportion of patients who were actually retested in each group of CT-based probability of COVID-19