Field comparison of the interferon‐gamma assay and the intradermal tuberculin test for the diagnosis of bovine tuberculosis

TLDR

The study compared the gamma interferon assay and the single intradermal tuberculin test in Australian cattle, testing over 6000 animals from TB‑free herds for specificity and evaluating sensitivity in depopulated herds. The IFN‑γ assay showed 96.2–98.1% specificity and 76.8–93.6% sensitivity, outperforming the tuberculin test, and a parallel test achieved 95.2% sensitivity, making it a valuable tool for the Australian eradication campaign.

Abstract

SUMMARY An extensive field comparison of the gamma interferon (IFN‐γ) assay and the single intradermal tuberculin test for the diagnosis of bovine tuberculosis was conducted in Australia. The specificity of the IFN‐γ assay was determined by testing more than 6000 cattle from tuberculosis‐free herds and varied from 96.2% to 98.1%, depending on the cut‐off point chosen to define a positive reactor. For the sensitivity trial, cattle from herds being de‐populated because of bovine tuberculosis were examined with both assays. The sensitivity of the IFN‐γ assay was shown to be significantly higher than the single intradermal tuberculin test and varied from 76.8% to 93.6% depending on the method of interpretation. A maximum overall sensitivity of 95.2% was obtained by testing with the IFN‐γ and the tuberculin test in parallel. The superior sensitivity of the IFN‐γ assay and the ability to adjust the sensitivity of the system depending on the task involved, will provide the Australian Tuberculosis Eradication Campaign with a valuable additional test to enable it to accomplish its goals.