In my experiences, if an interviewer directly ask you if you have been accepted elsewhere out of the blues (no follow-up or precursor question) then it's a sign that he is thinking of having adcom waitlist/reject you. I think it's so that he/she won't feel bad having you rejected.
Another sign is if the interviewer gave a talk advising you on something related to your career path. My theory on this is that they will have you rejected/waitlisted and therefore do not expect to see you again. Thus they figure they should share their wisdom before you leave.
Finally, you know you are rejected for sure when the interviewer advises you to expand your horizon and go to a medical school located somewhere you have never lived at before. Then proceeds to list some examples of medical schools to look at. (This was from my undergrad school)
Another sign is if the interviewer gave a talk advising you on something related to your career path. My theory on this is that they will have you rejected/waitlisted and therefore do not expect to see you again. Thus they figure they should share their wisdom before you leave.
Finally, you know you are rejected for sure when the interviewer advises you to expand your horizon and go to a medical school located somewhere you have never lived at before. Then proceeds to list some examples of medical schools to look at. (This was from my undergrad school)