Table 2.
Sensitivity, specificity, and Kappa index of each antigen determined by ELISA*
| Antigens | Median values (AU) | Sp (%) | Se (%) | Kappa index | |
|---|---|---|---|---|---|
| ChD (N = 228) | nChD (N = 108) | ||||
| Trypanosoma cruzi | 4.31 (2.61–6.05) | 0.39 (0.09–1.34) | 89.8 | 99.6 | 0.91 |
| JL7 | 4.97 (1.11–9.99) | 0.55 (0.12–0.89) | 100 | 95.2 | 0.93 |
| P013 | 2.46 (0.35–13.64) | 0.20 (0.00–0.60) | 97.2 | 82.5 | 0.74 |
| R13 | 1.38 (0.21–10.29) | 0.21 (0.01–1.64) | 85.1 | 61.4 | 0.41 |
| JL18 | 0.83 (0.22–2.66) | 0.52 (0.11–1.59) | 78.7 | 37.3 | 0.14 |
| JL19 | 0.87 (0.20–2.44) | 0.58 (0.05–1.67) | 75.0 | 40.4 | 0.13 |
| P0β | 0.44 (0.00–7.04) | 0.23 (0.00–1.98) | 86.1 | 28.5 | 0.12 |
ELISA plates were coated with 50 ng protein/well of T. cruzi epimastigote lysate, 2 μg/well of recombinant protein JL7 or 2 μM of peptides coupled to bovine serum albumin (BSA) in 50 μL buffer carbonate. Serum samples were diluted 1/400. All samples were tested in duplicate, and sera from six healthy individuals were loaded on the same plate to determine cut-off value, as the optical density (OD) mean value plus three standard deviations. Antibody level, in arbitrary units (AU), was calculated as ratio (OD value of each serum samples/cut-off value) and, the results were expressed as median values (5th–95th percentiles).
ChD = Chagas disease; nChD = no Chagas disease; N = number of individuals; Sp = specificity; Se = sensitivity.