Table 1.
Clinical performance of three anti‐SARS‐CoV‐2 immunoassays since symptom onset with the manufacturer's cut‐off and with optimized cut‐offs
| 0–6 d | 7–13 d | 14–20 d | 21–27 d | ≥28 d | Specificity (%) and 95% CI | Specificity (%) and 95% CI | Specificity (%) and 95% CI | |||
|---|---|---|---|---|---|---|---|---|---|---|
| n | 23 | 27 | 24 | 23 | 40 | (combined, n = 141) | (HVs, n = 38) | (cross‐reactivity, n = 103) | ||
| EUROIMMUN, IgGa | True positive | 4 | 19 | 23 | 20 | 36 | 96.5 (91.9 | 97.4% (86.2%–99.9%) | 96.1% (90.4%–98.9%) | |
| Ratio ≥ 0.80 | False negative | 19 | 8 | 1 | 3 | 4 | ||||
| Sensitivity (%) and 95% CI | 17.4 (5.0 | 70.4 (49.8 | 95.8 (78.9 | 87.0 (66.4 | 90.0 (76.3 | |||||
| True positive | 4 | 20 | 23 | 21 | 39 | 94.3 (89.1 | NA | NA | ||
| Ratio > 0.40 | False negative | 19 | 7 | 1 | 2 | 1 | ||||
| Sensitivity (%) and 95% CI | 17.4 (5.0 | 74.1 (53.7 | 95.8 (78.9 | 91.3 (72.0 | 97.5 (86.8 | |||||
| LIAISON, IgG | True positive | 3 | 9 | 20 | 20 | 37 | ||||
| AU/ml ≥ 12.0 | False negative | 20 | 18 | 4 | 3 | 3 | 97.9 (93.9%–99.6%) | 100% (90.8‐100%) | 97.1% (91.7%–99.4%) | |
| Sensitivity (%) and 95% CI | 13.0 (2.8%–33.6%) | 33.3 (16.5%–54.0%) | 83.3 (62.6%–95.3%) | 87.0 (66.4%–97.2%) | 92.5 (79.6%–98.4%) | |||||
| AU/ml > 3.94 | True positive | 6 | 15 | 23 | 22 | 39 | ||||
| False negative | 17 | 12 | 1 | 1 | 1 | 91.5 (85.6%–95.5%) | NA | NA | ||
| Sensitivity (%) and 95% CI | 26.1 (10.2%–48.4%) | 55.6 (35.3%–74.5%) | 95.8 (78.9%–99.9%) | 95.7 (78.1%–99.9%) | 97.5 (86.8%–99.9%) | |||||
| Elecsys, total antibodies | True positive | 4 | 19 | 21 | 20 | 39 | ||||
| COI ≥ 1.00 | False negative | 19 | 8 | 3 | 3 | 1 | 100 (97.4%–100%) | 100% (90.8‐100%) | 100% (96.5‐100%) | |
| Sensitivity (%) and 95% CI | 17.4 (5.0%–38.8%) | 70.4 (49.8%–86.3%) | 87.5 (67.6%–97.3%) | 87.0 (66.4%–97.2%) | 97.5 (86.8%–99.9%) | |||||
| True positive | 6 | 23 | 22 | 21 | 40 | |||||
| COI > 0.165 | False negative | 17 | 4 | 2 | 2 | 0 | 100 (97.4%–100%) | NA | NA | |
| Sensitivity (%) and 95% CI | 26.1 (10.2%–48.4%) | 85.2 (66.3%–95.8%) | 91.7 (73.0%–99.0%) | 91.3 (72.0%–98.9%) | 100 (91.2%–100%) |
Abbreviations: CI, confidence interval; HV, healthy volunteer.
a
The EUROIMMUN IgG assay is also sensitive to IgA and IgM, according to the insert kit of the manufacturer.