[user104658]

Surely most female to male post-op transsexuals would have had a full hysterectomy, and therefore not have a cervix, and therefore not require smear tests?

Doctors should refer to patients as whatever they are officially registered as, and also they should be aware of the person's full medical history and medically treat that person accordingly. Notes about any actual physical transition will be in the patients file so their doctor will know from that... They aren't just going on whether it says "Mr" or "Ms" in the title.