Worst example of this I've come across was in our local paper. A young girl (about 19 or so) had gone to her GP because of her bad head pain - who immediately diagnosed meningitis and sent her to A&E for treatment.
Just so happened that she also happened to have cystic fibrosis (I think - a while since I read the story, but something of that ilk) so needed to go to A&E on a fairly regular basis for treatment for problems relating to that, so her notes had CF written in very large letters across the top.
The doctors and nurses didn't look at her GP's admission note, or listen to her saying about her head pain and the rash that was getting bigger and bigger on her. Whenever she asked for help and treatment they kept saying that her CF didn't seem to be too bad and they were busy so they would be with her later. Well yes, that would be because she wasn't in there for problems with her CF. She tried calling her mum and she rang in (but wasn't able to go in) to ask them to look at her dd, but again they told her to stop worrying, they knew how to control her CF.
She had been in there for hours and was pretty much unconscious when they finally got to her - although they gave her antibiotics then, she died soon after 
whereas the GP thought that if they had given them to her when she arrived - as they would have done for any other 'no other problems' patient with a note like that from the GP - he was pretty sure that she would have been OK (obviously you can never tell with something like menigitis - but you can say she would have had a damn sight better chance if she had had the antibiotics when she arrived).