Table 2.
Specificity and sensitivity values obtained with 12 interpretative criteria of the IFN-γ test and cutoff values applied in the study for the diagnosis of Mycobacterium avium subsp. paratuberculosis (MAP) infected cattle.
| Interpretative criteria | SP (CI 95%) | SE (CI 95%) | Accuracy (A CI 95%) | AUC* | Y | |
|---|---|---|---|---|---|---|
| 1 | A-PBS > 0.05 = MAP | 88.5% (80.3–96.7%) | 85.1% (76.3–93.8%) | 86.8% (80.7–92.7%) | 0.868 | 73.6% |
| Ja-PBS > 0.05 = MAP | 93.4% (84.1–98.2%) | 88.1% (77.8–94.7%) | 90.6% (85.5–95.7%) | 0.908 | 81.5% | |
| Jb-PBS > 0.05 = MAP | 91.8% (81.9–97.3%) | 100.0% (94.1–100.0%) | 89.8% (84.5–95.1%) | 0.899 | 79.9% | |
| 2 | A-PBS > 0.1 = MAP | 95.1% (89.5–100%) | 76.1% (65.6–86.6%) | 85.2% (78.9–91.4%) | 0.856 | 71.2% |
| Ja-PBS > 0.1 = MAP | 100.0% (94.1–100.0%) | 77.6% (65.8–86.9%) | 88.3% (82.6–93.9%) | 0.888 | 77.6% | |
| Jb-PBS > 0.1 = MAP | 100.0% (94.1–100.0%) | 80.6% (69.1–89.2%) | 89.8% (84.5–95.1%) | 0.903 | 80.6% | |
| 3 | A-PBS > 0.2 = MAP | 100.0% (94.1–100.0%) | 58.2% (45.5–70.0%) | 78.1% (70.8–85.3%) | 0.791 | 58.2% |
| Ja-PBS > 0.2 = MAP | 100.0% (94.1–100.0%) | 67.2% (54.6–78.2%) | 82.8% (76.1–89.4%) | 0.836 | 67.2% | |
| Jb-PBS > 0.2 = MAP | 100.0% (94.1–100.0%) | 62.7% (50.1–74.2%) | 80.4% (73.5–87.4%) | 0.813 | 62.7% | |
| 4 | A-(2 * PBS) > 0 = MAP | 90.2% (79.8–96.3%) | 79.0% (67.4–88.1%) | 84.3% (77.9–90.7%) | 0.846 | 69.2% |
| Ja-(2 * PBS) > 0 = MAP | 98.4% (91.2–99.9%) | 79.1% (67.4–88.1%) | 88.2% (82.6–93.9%) | 0.887 | 77.5% | |
| Jb-(2 * PBS) > 0 = MAP | 93.4% (84.1–98.2%) | 82.1% (70.8–90.4%) | 87.5% (81.6–93.3%) | 0.878 | 75.5% | |
| 5 | A-(2 * PBS) > 0.04 = MAP | 95.1% (86.3–99.0%) | 73.1% (60.9–83.2%) | 83.6% (77.1–90.1%) | 0.841 | 68.2% |
| Ja-(2 * PBS) > 0.04 = MAP | 100.0% (94.1–100.0%) | 71.6% (59.3–82.0%) | 85.1% (78.9–91.3%) | 0.858 | 71.6% | |
| Jb-(2 * PBS) > 0.04 = MAP | 100.0% (94.1–100.0%) | 70.2% (57.7–80.7%) | 83.5% (77.0–90.0%) | 0.85 | 70.2% | |
| 6 | If PPDBov and/or PPDAv and/or PPDJ > 2 * PBS, then apply PPDBov/PPDAv and/or PPDBov/PPDJ | |||||
| B/A ≤ 0.9 = MAP | 90.2% (79.8–96.3%) | 81.3% (69.5–89.9%) | 83.6% (77.1–90.1%) | 0.857 | 71.4% | |
| B/Ja ≤ 0.9 = MAP | 100.0% (93.5–100.0%) | 78.7% (66.3–88.1%) | 82.8% (76.1–89.4%) | 0.893 | 77.0% | |
| B/Jb ≤ 0.90 = MAP | 94.9% (85.8–98.9%) | 81.5% (70.0–90.1%) | 85.1% (78.9–91.3%) | 0.882 | 69.3% | |
| 7 | If PPDAv and PPDJ > 2 * PBS, then apply PPDAv/PPDJ | |||||
| A/Ja ≤ 0.90 = MAP | 100.0% (93.5–100.0%) | 68.4% (51.3–82.5%) | 63.2% (54.8–71.7%) | 0.842 | 68.4% | |
| A/Jb ≤ 0.90 = MAP | 98.2% (90.3–99.9%) | 73.7% (56.9–86.6%) | 64.0% (55.6–72.4%) | 0.859 | 73.2% | |
| 8 | Ja/B > 1 = MAP | 75.0% (62.7–85.5%) | 88.0% (77.8–94.7%) | 82.0% (75.2–88.7%) | 0.817 | 63.0% |
| Jb/B > 1 = MAP | 69.0% (55.7–80.1%) | 94.0% (85.4–98.4%) | 82.0% (75.2–88.7%) | 0.814 | 63.0% | |
| 9 | Ja/A > 1 = MAP | 90.2% (79.8–96.3%) | 55.2% (42.6–67.4%) | 71.8% (63.9–79.7%) | 0.727 | 45.4% |
| Jb/A > 1 = MAP | 85.3% (73.8–93.0%) | 53.7% (41.1–66.0%) | 68.7% (60.6–76.8%) | 0.695 | 39.0% | |
| 10 | B/A > B/Ja = MAP | 90.2% (79.8–96.3%) | 55.0% (42.6–67.4%) | 71.8% (63.9–79.7%) | 0.727 | 45.0% |
| B/A > B/Jb = MAP | 85.0% (73.8–93.0%) | 54.0% (41.1–66.0%) | 68.7% (60.6–76.8%) | 0.695 | 39.0% | |
| 11 | Ja-A > 0.1 = MAP | 100.0% (94.1–100.0%) | 25.4% (15.5–37.5%) | 60.9% (52.3–69.5%) | 0.627 | 25.4% |
| Jb-A > 0.1 = MAP | 100.0% (94.1–100.0%) | 28.9% (16.8–39.1%) | 61.7% (53.1–70.2%) | 0.634 | 28.9% | |
| 12 | Ja-A > 0.05 = MAP | 100.0% (94.1–100.0%) | 35.0% (24.5–48.5%) | 66.4% (58.1–74.6%) | 0.679 | 35.0% |
| Jb-A > 0.05 = MAP | 98.4% (91.2–99.9%) | 37.3% (25.8–50.0%) | 66.4% (58.1–74.6%) | 0.678 | 35.7% | |
PPD, purified protein derivative; PPDBov or B, bovine PPD; PPDAv or A, avian PPD; PPDJ, Johnin PPD; Ja, Johnin PPD from strain A; Jb, Johnin PPD from strain B; PBS, phosphate-buffered saline; SP CI 95%, specificity and confidence interval 95%; SE CI 95%, sensitivity and confidence interval 95%; A CI 95%, accuracy and confidence interval 95%; AUC, area under the ROC curve; ROC, receiver operating characteristic; Y, Youden's index. The asterisk symbol (*) is used to indicate the mathematical operation of multiplication.