Table 6. IgG avidity ELISA assays using recombinant proteins and TLA to discriminate among samples from suspected acute (I) vs. chronic (II) phase of T. gondii infection patient groups.
| ANTIGEN | ROC cut-off | Undetermined zone “borderline AI” |
Avidity index (AI) | AUC | Sensitivity, % | Specificity, % | |
|---|---|---|---|---|---|---|---|
| GROUP I (n = 29) |
GROUP II (n = 31) | ||||||
| SAG2-GRA1-ROP1 | 0.3325 | 0.2993–0.3656 | L: 26 B: 2 H: 1 |
L: 0 B: 3 H: 28 |
0.9956 | 100 | 96.6 |
| SAG2-GRA1-ROP1-AMA1N | 0.3433 | 0.3090–0.3776 | L: 27 B: 2 H: 0 |
L: 0 B: 6 H: 25 |
0.9989 | 96.8 | 100 |
| AMA1N-SAG2-GRA1-ROP1 | 0.3882 | 0.3494–0.4270 | L: 24 B: 5 H: 0 |
L: 0 B: 3 H: 28 |
0.9978 | 96.8 | 100 |
| AMA1C-SAG2-GRA1-ROP1 | 0.3862 | 0.3476–0.4248 | L: 22 B: 7 H: 0 |
L: 0 B: 5 H: 26 |
0.9700 | 87.1 | 100 |
| AMA1-SAG2-GRA1-ROP1 | 0.4068 | 0.3661–0.4475 | L: 28 B: 1 H: 0 |
L: 0 B: 2 H: 29 |
1.0000 | 100 | 100 |
| TLA | 0.4102 | 0.3692–0.4512 | L: 26 B: 3 H: 0 |
L: 0 B: 1 H: 30 |
1.0000 | 100 | 100 |
Serum groups: I–suspected acute phase of T. gondii infection (IgM +; IgG +; low avidity), n = 29. II–chronic T. gondii infection (IgM–; IgG +; high avidity), n = 31. AI–avidity index; L–low avidity index; B–borderline avidity index; H–high avidity index. Sensitivity and specificity were:—determined using the cut-off value obtained by ROC analysis for the best discrimination.—calculated taking into account samples displaying AI values out of the undetermined zone