Table 2:
Performance characteristics of single and two-antigen approaches using US and population-specific cutoffs in Malian positive control and negative control samples.
| US cutoffs | Arithmetic Malian cutoffs (mean + 2SD) |
Arithmetic Malian cutoffs (mean + 3SD) |
Arithmetic Malian cutoffs (mean + 4SD) |
ROC curve Malian cutoffs |
|
|---|---|---|---|---|---|
| Single antigen: Spike | |||||
| Threshold (OD) | 0.674 | 0.791 | 1.041 | 1.291 | 0.743 |
| Sensitivity (95% CI) | 82.6% (61.2-95.1) | 82.6% (61.2-95.1) | 82.6% (61.2-95.1) | 78.3% (56.3-92.5) | 82.6% (61.2-95.1) |
| Specificity (95% CI) | 92.9% (89.5-95.5) | 96.1% (93.4-98.0) | 97.4% (95.0-98.9) | 98.7% (96.7-99.7) | 95.5% (92.6-97.5) |
| Single antigen: RBD | |||||
| Threshold (OD) | 0.306 | 1.183 | 1.625 | 2.067 | 0.766 |
| Sensitivity (95% CI) | 82.6% (61.2-95.1) | 60.9% (38.5-80.3) | 43.5% (23.2-65.5) | 39.1% (19.7-61.5) | 78.3% (56.3-92.5) |
| Specificity (95% CI) | 76.5% (71.4-81.1) | 96.5% (93.8-98.2) | 97.1% (94.6-98.7) | 98.1% (95.9-99.3) | 94.5% (91.4-96.8) |
| Two-antigen: Spike and RBD | |||||
| Sensitivity (%, 95% CI) | 78.3% (56.3-92.5) | 56.5% (34.5-76.8) | 43.5% (23.2-65.5) | 39.1% (19.7-61.5) | 73.9% (51.6-89.8) |
| Specificity (%, 95% CI) | 97.4% (95.0-98.9) | 99.7% (98.2-100) | 99.7% (98.2-100) | 100% (98.8-100) | 99.4% (97.7-99.9) |