Bovine Tuberculosis: Testing
The question
To ask the Secretary of State for Environment, Food and Rural Affairs, what assessment her Department has made of the reliability of the tuberculin skin test currently used for detecting bovine tuberculosis.
Answered by Dame Angela Eagle
The tuberculin skin test, also known as the Single Intradermal Comparative Cervical Tuberculin (SICCT) test, is the primary screening test for TB in cattle in the UK and the internationally accepted standard for detecting TB in cattle.
No diagnostic test is fully accurate. At standard interpretation, the SICCT test has a very high specificity, estimated to be 99.98% in Great Britain, meaning false positives are extremely rare. However, its sensitivity is around 70-80%, so about one quarter of infected animals in a herd may not be detected after a single round of testing. This is why herds experiencing a TB breakdown are tested more frequently using a severe interpretation until they achieve two consecutive negative tests. The SICCT test may be supplemented by more sensitive ancillary tests, such as the interferon-gamma (IFN-γ) blood test, to support earlier detection of infected animals and strengthen disease control.
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