TABLE 2.

Number of animals positive for subclinical paraTB by IFN-γ test and estimated specificity with different antigen stimulations and different interpretation criteria

Interpretation criterion for paraTBNo. of cows positive (% specificity)
5 noninfected herds (n = 116)10 infected herds (n = 249)
PPDjPPDaPPDj + PPDaaPPDjPPDaPPDj + PPDa
Fixed difference from no-antigen stimulation
    1. PPDxb-PBS > 0.0523 (80)c53 (54)20169193164
    2. PPDx-PBS > 0.112 (90)c36 (69)12137163135
3. Estimated difference from no-antigen stimulation
    PPDj-PBS > 0.2542 (98)83
    PPDa-PBS > 0.4536 (95)18474
4. Relative to no-antigen stimulation, 2 and PPDx/PBS > 47 (95)24 (79)5114143109
Relative to control antigen
    5. 1 and PPDx > PPDb6 (95)42 (64)4127171124
    6. 2 and PPDx > PPDb2 (98)27 (77)2112149109
    7. 3 and PPDx > PPDb1 (99)6 (95)1758267
IDEXX
    8. 1 and PPDb/PPDx < 0.713 (97)29 (75)29314190
    9. 2 and PPDb/PPDx < 0.712 (98)22 (81)28912785
    10. 3 and PPDb/PPDx < 0.711 (99)4 (97)1647557
  • a PPDj + PPDa indicates the number of animals with paraTB-positive results in both PPDj and PPDa tests.

  • b PPDx relates to either PPDj or PPDa as a stimulant in whole-blood cultures.

  • c An estimate of test specificity for bovine paraTB was calculated as [N −n(pos)]/N × 100, where N is the number of tested animals (N = 116) and n(pos) is the number of (false) test-positive animals.