There has been some work by Queen's University in Belfast indicating dogs may be able to detect their type 1 diabetic owners hypoglycemia. There have also been reports of dogs being able to detect melanoma as well as bladder cancer. Dogs have a very highly developed sense of smell, and are extremely tuned in to their owners behavior, so I see no reason why they wouldn't make excellent diagnosticians! However, like many of our synthetic doagnostic tools, specificity of the "doggy nose" test in a random population I expect would be low because of the many inter-individual variations.
Marion Co Public Health Department