Private vs socialised healthcare could have a big effect on diagnoses. When patients can just keep going to doctors until they get the diagnosis they want, doctors that more readily make a diagnosis will make more money.
With socialised healthcare the doctors have enough traffic to not need more clients usually. I don't think I've met a doctor in Poland (even paying out of pocket) who wanted me to come more often than absolutely necessary.
Sorry, should have made this clearer. I mean private healthcare leads to more diagnoses. In socialised healthcare the doctors have no financial incentive. Hence the original comment saying that diagnoses are less common in Europe.