I keep track of research where animals are expected to communicate. Dogs are asked to sit, to alert, to push, etc. to indicate they have sensed something. My passion is dealing with teaching them to communicate in detail by signing using a structured-made for their body-language.
Recent work at Berkeley indicates that puppies with just weeks of training can communicate that they sensed a particular odor in breath. That odor was specific to lung cancer. They did this over 98% of the time and they never misdiagnosed (false positive). The remarkable aspect of the study was not just they could sense the specific odor, but that these were just plain puppies with simple obedience skills and it took a few weeks. They were not specially bred dogs.
This really opens up so much for dogs and people. Imagine a class where dogs get 'health training' where they learn to sniff various diseases for their owner. I can see that supplementing current diagnostics.
I'm investigating diabetics having their own dogs detect low blood sugar or high blood sugar. This can be done with specially trained dogs, but imagine training your own dog to do this!