Since positive and negative politeness applies to all kinds of dialogues, it also applies to the medical language. Nonetheless, it is mostly negative politeness in medical discourse because doctors do not want to be impeded by the patients. They refused to be challenged by the patients; therefore, they ignore any symptoms or signs of illness that are thought to be irrelevant.
Doctors are not analyzing the patient's illness like a English major student analyzing a novel. A novel would have a few different ways to interpret, whereas, in medical discourse, there is only two ways; if one symptom is not found in the patient, then they move to the next one to name the illness. It is similar to a formula tree. Doctors are tracing branches to meet the end.