Table 2.
Liu analysis ELISA titer cut-points across different LPS-specific immune parameters Differentiating vaccinated subjects with consensus shigellosis from vaccinated subjects without consensus shigellosis post-challenge.
| Immune Parameterxav | ROC AUCa | Optimal Cut-Pointb | Shigellosis Outcome (n) | Relative Riskc (P-Value)d | % Efficacye (P-Value)f | SENSg | SPECh | PPVi | NPVj | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| With | Without | Total | |||||||||
| Serum IgG | |||||||||||
| Day 28 Titer | 0.805 | ≥12,800 | 5 | 16 | 21 | 0.357 | 59.4% | 84.2% | 54.5% | 76.2% | 66.7% |
| <12,800 | 6 | 3 | 9 | (0.042) | (0.021) | ||||||
| Day 56 Titer | 0.792 | ≥25,600 | 3 | 12 | 15 | 0.375 | 65.9% | 63.2% | 72.7% | 80.0% | 53.3% |
| <25,600 | 8 | 7 | 15 | (0.128) | (0.025) | ||||||
| Max Titer | 0.755 | ≥12,800 | 7 | 17 | 24 | 0.438 | 50.2% | 89.5% | 36.4% | 70.8% | 66.7% |
| <12,800 | 4 | 2 | 6 | (0.156) | (0.052) | ||||||
| Peak Fold Rise | 0.842 | ≥8 | 4 | 16 | 20 | 0.286 | 65.9% | 84.2% | 63.6% | 80.0% | 70.0% |
| <8 | 7 | 3 | 10 | (0.015) | (0.009) | ||||||
| Serum IgA | |||||||||||
| Day 28 Titer | 0.718 | ≥800 | 5 | 16 | 21 | 0.357 | 59.4% | 84.2% | 54.5% | 76.2% | 66.7% |
| <800 | 6 | 3 | 9 | (0.042) | (0.021) | ||||||
| Day 56 Titer | 0.726 | ≥800 | 6 | 16 | 22 | 0.436 | 53.5% | 84.2% | 45.5% | 72.7% | 62.5% |
| <800 | 5 | 3 | 8 | (0.104) | (0.046) | ||||||
| Max Titer | 0.752 | ≥1600 | 4 | 15 | 19 | 0.331 | 64.1% | 78.9% | 63.6% | 78.9% | 63.6% |
| <1600 | 7 | 4 | 11 | (0.047) | (0.017) | ||||||
| Peak Fold Rise | 0.674 | ≥8 | 6 | 17 | 23 | 0.365 | 55.5% | 89.5% | 45.5% | 73.9% | 71.4% |
| <8 | 5 | 2 | 7 | (0.068) | (0.026) | ||||||
| Serum IgG1 | |||||||||||
| Day 28 Titer | 0.742 | ≥100 | 1 | 11 | 12 | 0.150 | 85.8% | 57.9% | 90.9% | 91.7% | 55.6% |
| <100 | 10 | 8 | 18 | (0.018) | (0.005) | ||||||
| Day 56 Titer | 0.761 | ≥100 | 3 | 14 | 17 | 0.287 | 69.9% | 73.7% | 72.7% | 82.4% | 61.5% |
| <100 | 8 | 5 | 13 | (0.023) | (0.013) | ||||||
| Max Titer | 0.804 | ≥100 | 3 | 15 | 18 | 0.250 | 71.6% | 78.9% | 72.7% | 83.3% | 66.7% |
| <100 | 8 | 4 | 12 | (0.009) | (0.006) | ||||||
| Peak Fold Rise | 0.796 | ≥2 | 3 | 15 | 18 | 0.250 | 71.6% | 78.9% | 72.7% | 83.3% | 66.7% |
| <2 | 8 | 4 | 12 | (0.009) | (0.006) | ||||||
| Serum IgG2 | |||||||||||
| Day 28 Titer | 0.691 | ≥400 | 8 | 17 | 25 | 0.533 | 45.4% | 89.5% | 27.3% | 68.0% | 60.0% |
| <400 | 3 | 2 | 5 | (0.327) | 0.061 | ||||||
| Day 56 Titer | 0.699 | ≥800 | 6 | 17 | 23 | 0.365 | 55.5% | 89.5% | 45.5% | 73.9% | 71.4% |
| <800 | 5 | 2 | 7 | (0.068) | (0.026) | ||||||
| Max Titer | 0.711 | ≥800 | 6 | 17 | 23 | 0.365 | 55.5% | 89.5% | 45.5% | 73.9% | 71.4% |
| <800 | 5 | 2 | 7 | (0.068) | (0.026) | ||||||
| Peak Fold Rise | 0.803 | ≥4 | 5 | 16 | 21 | 0.357 | 59.4% | 84.2% | 54.5% | 76.2% | 66.7% |
| <4 | 6 | 3 | 9 | (0.042) | (0.021) | ||||||
| Day 28 Titer | 0.641 | ≥3162 | 5 | 13 | 18 | 0.556 | 52.6% | 68.4% | 54.5% | 72.2% | 50.0% |
| <3162 | 6 | 6 | 12 | (0.266) | (0.070) | ||||||
| Day 56 Titer | 0.780 | ≥3415 | 4 | 15 | 19 | 0.331 | 64.1% | 78.9% | 63.6% | 78.9% | 63.6% |
| <3415 | 7 | 4 | 11 | (0.047) | (0.017) | ||||||
| Max Titer | 0.708 | ≥2561 | 6 | 17 | 23 | 0.365 | 55.5% | 89.5% | 45.5% | 73.9% | 71.4% |
| <2561 | 5 | 2 | 7 | (0.068) | (0.023) | ||||||
| Peak Fold Rise | 0.763 | ≥6 | 5 | 15 | 20 | 0.417 | 57.4% | 78.9% | 54.5% | 75.0% | 60.0% |
| <6 | 6 | 4 | 10 | (0.108) | (0.040) | ||||||
| α4β7+ IgG | 0.882 | ≥2 | 3 | 17 | 20 | 0.150 | 74.4% | 100.0% | 66.7% | 85.0% | 100.0% |
| <2 | 6 | 0 | 6 | (0.0004) | (0.003) | ||||||
| α4β7- IgG | 0.797 | ≥2 | 3 | 15 | 18 | 0.222 | 71.6% | 88.2% | 66.7% | 83.3% | 75.0% |
| <2 | 6 | 2 | 8 | (0.008) | (0.006) | ||||||
| α4β7+ IgA | 0.696 | ≥2 | 3 | 12 | 15 | 0.367 | 65.9% | 70.6% | 66.7% | 80.0% | 54.5% |
| <2 | 6 | 5 | 11 | (0.103) | (0.025) | ||||||
| α4β7- IgA | 0.647 | ≥2 | 2 | 8 | 10 | 0.457 | 65.9% | 47.1% | 77.8% | 80.0% | 43.8% |
| <2 | 7 | 9 | 16 | (0.399) | (0.065) | ||||||
| IgG | 0.729 | ≥32 | 4 | 10 | 14 | 0.653 | 51.3% | 52.6% | 63.6% | 71.4% | 43.8% |
| <32 | 7 | 9 | 16 | (0.466) | (0.104) | ||||||
| IgA | 0.590 | ≥64 | 7 | 15 | 22 | 0.636 | 45.7% | 78.9% | 36.4% | 68.2% | 50.0% |
| <64 | 4 | 4 | 8 | (0.417) | (0.089) | ||||||
Area under the curve (AUC) of a receiver operator characteristic (ROC) graph.
Liu cut-point analysis used to determine the optimal point in the AUC which maximizes the product of sensitivity and specificity of the ROC.
Calculated as: (shigellosis rate among vaccinees at or above the optimal cut-point / shigellosis rate among vaccinees below the optimal cut-point).
P-value determined by Fisher's Exact Test comparing shigellosis rate among vaccinees at or above the optimal cut-point versus shigellosis rate among vaccinees below the optimal cut-point.
Calculated as: [1 – (shigellosis rate among vaccinees at or above the optimal cut-point / shigellosis rate among placebo recipients)] x 100.
P-value determined by Fisher's Exact Test comparing shigellosis rate among vaccinees at or above the optimal cut-point versus shigellosis rate among placebo recipients.
Sensitivity = (number of subjects without shigellosis at or above the optimal cut-point / total number of subjects without shigellosis).
Specificity = (number of subjects with shigellosis at or above the optimal cut-point / total number of subjects with shigellosis).
Positive Predictive Value = (number of subjects without shigellosis at or above the optimal cut-point / total number of subjects at or above the optimal cut-point).
Negative Predictive Value = (number of subjects with shigellosis below the optimal cut-point / total number of subjects below the optimal cut-point).