I lived with a persistent and occasionally debilitating health problem for nearly a decade while being brushed off by clueless doctors.
Finally, I wound up in the ER (again) being served by a guy who actually took the time / had the ability to interpret a blood test.
Not long after that I was having a large, old and thankfully benign tumor removed.
As I understand the issue, a blood test would have revealed this at any point and likely even before the 10 or so years I'd been having symptoms.
Personally, I'm given to thinking that we tend to give folks in medicine too much credit.
Sure, I think it reasonable to expect that someone who has made it through medical school and successfully practices is above average in some regards - relative to the broad population.
However, within the field, I expect that incompetence / apathy is just as prevalent as it is in any other profession.