Doctors are supposed to be experts on diseases because this is what they study in medical college, and they practice medicine all their lives, treating ill patients.
However, the reality is that they’re not, because they have a very prejudiced point of view. Let me explain.
Thus, doctors don’t appreciate normal biological variations because they only see patients who think they have a medical problem. Doctors don’t see healthy people because they don’t seek medical attention! As a result of this bias, any time a doctor sees something which is abnormal (either on clinical examination, a lab test or a scan result), he jumps to the conclusion that it is this abnormal finding which is the reason for the illness – while the reality is that the so-called deviation from the normal could just be an anatomical or physiological variant.
Similarly, doctors don’t have a good idea of the natural history of a disease. This is because they only get to see those patients who choose to follow up with them. However, lots of patients don’t come back – either because they get better on their own, or they find another doctor. This means that the doctor’s sample size is biased, and this can confuse him.
Thus, an oncologist’s understanding of breast cancer is based only on that small group of patients who follow up with them – they have no idea what happens to the rest.
This is why eminence-based medicine, which relies on the doctor’s personal experiences and prejudices, can be so unreliable. This is especially true for older and more senior doctors, who become dogmatic, and start believing they know everything there is so know because of their years of experience!