DEAR MISS MANNERS: I work in health care and frequently call patients regarding their appointments. I use their first names if we are already acquainted, and Mr./Mrs. for people I am not familiar with -- and for older patients, who seem to prefer the formality. However, I am less confident about addressing patients who have, or have had, titles. If the paperwork says “Dr.” (as in a Ph.D.), am I supposed to address them as such? I have yet to have a duke or duchess, but I do have members of congress, judges, senators, religious leaders and the like -- as well as people who have held such positions in the past.