Table 1.
Performance Characteristics of Single- and 2-Antigen Approaches Using US and Population-Specific Cutoffs in Malian Positive Control and Negative Control Samples
| Configuration | US Cutoffs | Arithmetic Malian Cutoffs (Mean + 2 SD) | Arithmetic Malian Cutoffs (Mean + 3 SD) | Arithmetic Malian Cutoffs (Mean + 4 SD) | 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) |
Abbreviations: CI, confidence interval; OD, optical density; RBD, receptor binding domain; ROC, receiver operating characteristic; SD, standard deviation.