I do think networks are communicating these days. However, I think you probably somewhere along the line agreed to it. I had my annual physical and they had my life at their finger tips. They knew I was overdue for my annual pap smear and hadn't had one yet this year just from a few clicks on the computer. But if I remember correctly, I signed about 4 things and one of them was this piece of it. They called it some kind of network. Typically, doctors knowing the other specialty isn't a horrible thing and sharing your med file means everyone is on the same page. Did you not want your PC to know?
Hello~I know over here in New Zealand, all your records, prescriptions, etc are entered into the network, thus, no matter what doctors you see, hospital or pharmacy, your info is just a click away. All of us have a number, that means we are in the "system" I don't mind it, I mean, what do I have to hide. I am originally from America, I moved here to New Zealand 7 years ago, back then, I don't think America had this network you are talking about, but if they had, I would have signed the release form. I guess it is up to each individual.
We can't opt-out of it over here,but I am sure if the USA you can.