Although a number of blood-based diagnostic tests for the detection of Mycobacterium bovis (M.bovis) infection in badgers have been developed through Defra-funded research, none of these is suitable for extensive field use. Post-mortem inspection and culture of M.bovis remains the most reliable method of diagnosis.
The currently available blood tests have been validated using blood from both infected and uninfected badgers. They are currently used to measure immune responses in research projects such as the development of vaccines for badgers. A difference between the two populations can be measured, but no test is 100 per cent sensitive or specific, so some false positive and false negative results will occur. It is difficult to find populations of badgers that are truly negative for bovine tuberculosis.