I am about to run out my door and don't have time to make a lengthy post; but I want to say that this is an excellent thread!
Some of the advice given is just scary. The other thing that many people do not realize is that all of the information flying around is overwhelming. It takes time and a very schooled vet to examine, test and diagnose. It is not as simple as reading a few symptoms and knowing the results of one test. Just my quick two cents.