Methodology
Bulk tank milk samples were available from 247 SICCT positive UK herds and from 1,792 true negative reference herds from Norway, Denmark, Germany and Scotland. Bulk tank milk samples from breakdown herds were taken at the time of reading the SICCT test (TT2; non-boosted) and bulk tank milk samples were taken from bTB-free herds at random time points (non-boosted). Anamnestic bulk tank milk samples taken following removal of SICCT test positive animals were available from 20 bTB breakdown herds.
Sensitivity and specificity of the Enferplex Bovine TB antibody test using bovine bulk tank milk samples from SICCT positive and bTB free herds
Kappa Analysis: All samples: High sensitivity setting: 0.831 (95% CI 0.795 – 0.867); almost perfect agreement. All samples: High specificity setting: 0.772 (95% CI 0.730 – 0.813); substantial agreement.
Likelihood ratios for Enferplex Bovine TB antibody test using bulk tank milk samples from SICCT test positive herds
Results
Bulk Tank Milk
The diagnostic sensitivity of non-boosted bulk tank milk samples from SICCT positive animals (n = 247) was 77.7% and 71.7%, while the diagnostic specificity using 1792 bulk tank milk samples from bTB free animals was 99.8% and 99.9% using the high sensitivity and high specificity settings respectively.
Kappa analysis showed almost perfect agreement, while the positive LR was 348.2, negative LR was 0.223, and DOR of 1560.4 indicating good evidence for infection being present or absent respectively (Caraguel & Colling, 2021).
Significance/Impact:
Bulk tank milk testing using the highly specific and relatively sensitive Enferplex test would provide an easy, inexpensive and convenient method of screening dairy herds more frequently than is currently the case without causing any disruption.