I am struggling to define exactly what all needs to be done in order to bill an EM with 20610. Modifier 25 is a (Significant, separately identifiable E&M service by the same physician on the same day of the procedure), indicates that the patient’s condition required a significant, separately identifiable E&M service beyond the usual preoperative and postoperative care associated with the procedure or service.

How do we know what is the 'usual' preop care for an injection?