From what i've seen, at a vast majority of places nobody checks the history/ chart. I've been going to the same clinic for the last 5 years (admittedly not often, but still) and EVERY time i go in i have to explain things that i have specifically asked them to annotate in my chart, like that i outgrew a childhood iodine allergy. Yet every time im sitting in the room, they say "and you're allergic to iodine, right?". Because it's on page 1 of the chart and they cant be bothered to look at anything else. In some cases, they're just shit, in other cases they're too busy or their caseload is too big to take the time to even skim someone's chart for the basics, so whatever the patient tells them, they assume it's accurate.
I saw a woman admitted to the psych hospital twice in a year. Her psychiatrist had told her she was schizophrenic, and she had no reason to question him. So when several months after her baby was born, she began hearing voices telling her to hurt the baby, she assumed it was a schizophrenic episode and admitted herself for a med adjustment. The hospital didnt really look into it, just threw anti-psychotic medication at her until she was "stable" and sent her home. Some months later she attempted suicide and was diagnosed with post-partum depression, and medicated accordingly. That was expected to be the end of it, except she was in and out of the hospital a couple of times a year because even the "overkill" schizophrenia treatments did not really work (things like Clozapine et al). Finally, a doctor actually read her chart. And noticed that while she was often admitted for psychosis, it was frequently accompanied by severe agitation, pressured speech, inability to sleep etc. And other times she was admitted for suicidal depression, which the previous doctors had been kinda cramming into a psychosis-shaped box because they had been told her dx was schizophrenia and while depressive symptoms arent unheard of with that condition, the severity she was experiencing did not really fit the dx. The doctor realized that the woman was actually suffering from bipolar 1, and that her symptoms after the baby was born were actually post-partum psychosis which a bipolar patient is at increased risk for. The moral of this really long-winded story? Doctors very often rely on patient-reported information such as diagnoses, and dont do much digging. So if a patient walks in and says "i have X disease previously diagnosed, and i want treatment for it", there's a good chance the doctor will take that at face value rather than go to the trouble of starting the whole differential process over again.
For a genuinely sick patient, this can mean the wrong diagnosis can follow you around for years because nobody's willing to do the legwork to look deeper, and you've got no reason (being not a doctor yourself) to believe the diagnosis might be wrong. For a munchie, it means that if you can get a doctor just to say something like "it might be EDS", for example, that's enough grounds to say a doctor "diagnosed" you, and you can take that to the next doctor with full confidence that they will believe it.
