Both in veterinary practice and for the protection of human and animal health, veterinarians apply diagnostic tests on a routine basis. For example a dog owner may ask for a diagnostic to ensure the best care for his pet or for trade purposes a country is required to provide proof for freedom of a certain disease. Diagnostic test have many other applications such as disease surveys, individual animal travel or proving freedom from disease.

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In addition diagnosis often builds the basis for disease control measures. Examples include:

• Tuberculin test and eradication of tuberculosis in cattle
• Infectious Bovine Rhinotracheitis serologic screening and vaccination of positive animals

Diagnosis should therefore be based on facts (i.e. evidence-based) and not only on rough guesses!

This means you need to be able to:

• Validate new tests (comparing them against existing reference standards),
• Understand the properties of tests to assess their fit-for-purpose and
• Interpret the test results in the context of the test characteristics and the disease background (true prevalence)

Three Hereford heifers after a TB test in the United Kingdom. Reactors - cattle which produce an allergic reaction to the test, indicating antibodies to bovine tuberculosis are slaughtered and movements of an affected farm restricted [Source: Richard Webb].
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