Table 3.
Serum IgA responses to seven mycobacterial antigens.
| Group | ELISA index at 450 nm (mean ± SD) and positive rate (%) | ||||||
|---|---|---|---|---|---|---|---|
| ESAT-6 | CFP-10 | MDP1 | Ag85A | Acr | HBHA | HrpA | |
| Cut-off values | 1.496 | 0.567 | 1.115 | 0.577 | 0.738 | 1.015 | 0.901 |
| Negative control | 1.564 ± 1.533 32.4% |
1.007 ± 1.041 58.1% |
2.290 ± 2.277 63.5% |
1.354 ± 1.382 64.9% |
0.881 ± 0.739 41.9% |
1.132 ± 1.140 35.1% |
0.932 ± 0.813 39.2% |
| Active disease | 2.189 ± 2.192 59.5% |
1.246 ± 1.312 78.4% |
1.137 ± 0.828a
30.7% |
1.470 ± 1.664 85.2% |
1.252 ± 1.549b
58.0% |
1.713 ± 1.955 55.7% |
0.751 ± 0.333 29.5% |
| Past disease | 1.336 ± 1.128c
23.8% |
0.976 ± 0.715 72.6% |
1.166 ± 1.232d
34.5% |
1.037 ± 0.686 79.8% |
0.831 ± 0.495 50.0% |
1.283 ± 0.954 50.0% |
0.771 ± 0.356 35.7% |
| Latent TB infection | 0.783 ± 0.246e
0.0% |
0.793 ± 0.307 64.7% |
0.879 ± 0.297f
11.8% |
0.898 ± 0.395 58.8% |
0.606 ± 0.221 23.5% |
0.772 ± 0.299 17.6% |
0.595 ± 0.285 17.6% |
|
| |||||||
| AUROC | 0.63 | 0.53 | 0.66 | 0.57 | 0.59 | 0.62 | 0.53 |
a P < 0.01 (active versus control), b P < 0.05 (active versus past), c P < 0.01 (active versus past), d P < 0.01 (past versus control), e P < 0.05 (active versus latent), f P < 0.05 (latent versus control).
Optimal cut-off values were chosen when the Youden's index (sensitivity and specificity − 1) was maximal.
AUROC: areas under the receiver operating characteristic curve.