Table 1.
Chagas disease serology results in samples from Machala, Ecuador
| Screening Trypanosoma cruzi results | ORTHO T. cruzi ELISA test system* (n = 658) | |
|---|---|---|
| Positive | n (%) | 6/658 (0.9%) |
| Mean (SD) | 4.9 (1.36) | |
| Equivocal† | n (%) | 8/658 (1.2%) |
| Mean (SD) | 0.9 (0.13) | |
| Negative | n (%) | 644/658 (97.8%) |
| Mean (SD) | 0.18 (0.10) | |
| Confirmatory T. cruzi results | ORTHO T. cruzi ELISA test system* (n = 26) | Hemagen Chagas kit ELISA‡ (n = 26) | Chagatest ELISA‡ recomb. v.0.3 (n = 26) | Trypomastigote excreted–secreted antigens blot (n = 26) | Rapid test Chagas Detect Plus (n = 26) | |
|---|---|---|---|---|---|---|
| True positive | n (%) | 6/26 (23.1%) | 6/26 (23.1%) | 6/26 (23.1%) | 6/26 (23.1%) | 6/26 (23.1%) |
| Mean (SD) | 4.9 (1.36) | 1.3 (0.35) | 2.14 (0.92) | NA | NA | |
| False positive | n (%) | 0/26 (0%) | 1/26 (3.8%) | 0/26 (0%) | 0/26 (0%) | 4/26 (15.4%) |
| Mean (SD) | NA | 1.3 | NA | NA | NA | |
| Equivocal† | n (%) | 0/26 (0%) | 1/26 (3.8%) | 0/26 (0%) | 0/26 (0%) | 0/26 (0%) |
| Mean (SD) | NA | 0.2 | NA | NA | NA | |
| Negative§ | n (%) | 20/26 (76.9%) | 18/26 (69.2%) | 20/26 (76.9%) | 20/26 (76.9%) | 16/26 (61.5%) |
| Mean (SD) | 0.31 (0.10) | 0.1 (0.05) | 0.001 (0.001) | NA | NA | |
NA = not applicable.
* Mean and SD correspond to signal-to-cutoff ratio.
† Equivocal results were defined when discordant results were obtained in two independent measurements by the ORTHO T. cruzi ELISA test system, and Chagas Detect Plus, or when ELISA optical density (OD) values were 10% higher than the cutoff of the test by the Hemagen Chagas kit, and Chagatest ELISA recombinant v.3.0.
‡ Mean and SD correspond to OD.
§ Subset of samples matched to positive cases by age, gender, and geographical location.