Is the gamma interferon assay in cattle influenced by multiple tuberculin injections?

Along with other developed countries, Canada is interested in adopting the gamma interferon (IFN-gamma) assay to test for bovine tuberculosis (TB). This study compared results of using the IFN-gamma assay in a large number of field-tested cattle in Manitoba, some previously tested with a caudal fold test (CFT) only, and others injected with tuberculins for both a CFT and a comparative cervical test (CCT). Parallel testing further compared the IFN-gamma assay and CCT results with the confirmed TB status of the animal (culture, histopathologic examination, polymerase chain reaction).