Table 1.
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 | ||
|---|---|---|
| 1 | Difference between PPDAv and PBS value > 0.05 | If PPDAv – PBS > 0.05 = MAP |
| Difference between PPDJa or Jb and PBS value > 0.05 | If PPDJ – PBS > 0.05 = MAP | |
| 2 | Difference between PPDAv and PBS value > 0.1 | If PPDAv – PBS > 0.1 = MAP |
| Difference between PPDJa or Jb and PBS value > 0.1 | If PPDJ – PBS > 0.1 = MAP | |
| 3 | If the difference between the PPDAv value and PPDJa or Jb and PBS value is >0.2, the animal is considered MAP reactive | PPDAv – PBS > 0.2 = MAP |
| PPDJ – PBS > 0.2 = MAP | ||
| 4 | If the reaction to Italian PPDAv or PPD Ja or Jb is two-fold the PBS value, the animal is considered MAP reactive | PPDAv – (2 * PBS) > 0 = MAP |
| PPDJ – (2 * PBS) > 0 = MAP | ||
| 5 | Difference between PPDAv and twice the PBS value > 0.04 | If PPDAv – (2 * PBS) > 0.04 = MAP |
| Difference between PPDJa or Jb and twice the PBS value > 0.04 | If PPDJ – (2 * PBS) > 0.04 = MAP | |
| 6 | First level: | If PPDBov and PPDJ > 2 * PBS then apply PPDBov/PPDJ |
| Second level: | If PPDBov/PPDJ ≤ 0.9 = MAP and if PPDBov/PPDJ ≥ 1.1 = MB | |
| If PPDBov/PPDAv ≤ 0.9 = MAP and if PPDBov/PPDAv ≥ 1.1 = MB | ||
| In case of intermediate values, the result is inconclusive or not discriminant (ND). | ||
| 7 | First level: | If PPDAv and PPDJ > 2 * PBS then apply PPDBov/PPDJ |
| Second level: | If PPDAv/PPDJ ≤ 0.9 = MAP and If PPDAv/PPDJ ≥ 1.1 = MA | |
| In case of intermediate values, the result is inconclusive or non-discriminant (ND). | ||
| 8 | PPDJa or Jb and PPDBov ratio | If PPDJ/PPDBov > 1 = MAP |
| 9 | PPDJa or Jb and PPDAv ratio | If PPDJ/PPDAv > 1 = MAP |
| 10 | Comparison of the ratios between PPDBov and PPDAv and between PPDBov and PPDJa or Jb ratio | If PPDBov/PPDAv > PPDBov/PPDJ = MAP |
| 11 | Difference between PPDJa or Jb and PPDAv > 0.1 | If PPDJ – PPDAv > 0.1 = MAP |
| 12 | Difference between PPDJa or Jb and PPDAv > 0.05 | If PPDJ – PPDAv > 0.05 = MAP |
PPD, purified protein derivative; PPDBov, bovine PPD; PPDAv, avian PPD; PPDJ, Johnin PPD; PPDJa, Johnin PPD from strain A; PPDJb, Johnin PPD from strain B; PBS, phosphate-buffered saline. The asterisk symbol (*) is used to indicate the mathematical operation of multiplication.