It's an interesting question. Having a child with medical/developmental issues, there are procedures and tests that cause him discomfort, and I'll admit that unless we ABSOLUTELY have to do it, I avoid them... even if sometimes the results would be helpful. A lot of it goes back to when we were vaccinating, and I'm not even referring to the brain damage that resulted. I truly believe that he has emotional trauma from the experience. He cannot get bloodwork now without being sedated. It just destroys me how vaccination harmed his little life in a myriad of ways.
Sometimes we cannot avoid physical pain for our children in the name of finding medical answers. I also think that many health answers can be found for our children without any physical discomfort whatsoever... but it involves a bit more homework.
re: titers. The majority of parents I know don't even know what they are. Pet owners seem more informed about them. (This probably ties into our earlier pet vaccination post!)