Table 3.
Test Characteristics of the Elecsys Anti–SARS-CoV-2 S-Ab Assay Clinical Performancea
| S-Ab Assay Statistics | PCR Positive 0-6 Days (95% CI) | PCR Positive 7-13 Days (95% CI) | PCR Positive ≥14 Days (95% CI) |
|---|---|---|---|
| Sensitivity, % | 60.0 (46.5-72.4) | 78.1 (60.0-90.7) | 100 (83.2-100.0) |
| Specificity, % | 100 (93.3-100.0) | 100 (93.3-100.0) | 100 (93.3-100.0) |
| Disease prevalence, % | 10 | 10 | 10 |
| PPV, % | 100 | 100 | 100 |
| NPV, % | 95.7 (94.3-96.8) | 97.6 (95.5-98.8) | 100 |
| Accuracy, % | 96.0 (90.6-98.8) | 97.8 (92.0-99.8) | 100 (95.1-100.0) |
CI, confidence interval; NPV, negative predictive value; PPV, positive predictive value; S-Ab; spike protein antibody.
aA 10% disease prevalence was assumed for PPV, NPV, and accuracy calculations for samples grouped by collection time: 0 to 6 days, 7 to 13 days, and at or more than 14 days after initial confirmation of positivity by reverse transcription quantitative polymerase chain reaction (PCR).