One place worth looking is the University of Bath English Langauge Testing (UBELT).
They have developed and deliver various English languiage tests, for various medical professions, including nurses, which test the testee's communicative proficiency.
These tests are used by practicing professionals and are delivered a some European medical universities to certify their final year medical students.
Frustratingly, while UBELT sell a limited number of practice tests (which by the way are fantastic and have great listening test CDs, full of authentic content), I can't find any course books. Please let me know if you know of any.