Comparative Agreement of Intradermal Tuberculin Test and Interferon-Gamma Release Assay in Bovine Tuberculosis...

Bovine tuberculosis (bTB) remains endemic in southern Italy, particularly in Sicily, posing challenges for disease control and eradication. This study evaluated the diagnostic agreement between the intradermal tuberculin test (IDT), interferon-gamma release assay (IFN-γ), and post-mortem lesion detection in 1801 cattle from 44 herds in the province of Palermo during 2024-2025. Diagnostic agreement between IDT and IFN-γ was substantial in 2024 (κ = 0.731; 95% CI: 0.64-0.82; n = 991) and decreased to moderate in 2025 (κ = 0.453; 95% CI: 0.33-0.57; n = 572), reflecting a higher proportion of IFN-γ positive and inconclusive animals. An increase in inconclusive results for IFN-γ was observed in 2025, but the available data did not allow investigation of the factors underlying this difference. Agreement between ante-mortem tests and post-mortem lesion detection was poor in a selected subgroup of slaughtered animals, potentially subject to verification bias, highlighting the limitations of single diagnostic tools and the need for a complementary approach combining immunological and pathological methods. These findings support the interpretation of the complementary roles of IDT and IFN-γ within herd-level bTB surveillance, highlight the need for standardized protocols to manage inconclusive IFN-γ results, and underline the complementary contribution of post-mortem inspection within integrated surveillance strategies in endemic settings. Official confirmation of bovine tuberculosis relies on an integrated evaluation combining diagnostic results, post-mortem findings, and epidemiological investigations. Given the absence of a validated gold standard applicable to all animals in this observational dataset, the study was designed as a diagnostic agreement study rather than a formal accuracy assessment.