Directly from the USMLE:
Changes were introduced to the Step 2 CS examination program in mid-June 2012. These included changes to the patient note that examinees must complete after each standardized patient encounter.
As described in the Step 2 CS Content Description and General Information booklet, examinees should record pertinent medical history and physical examination findings obtained during the encounter, as well as initial differential diagnoses (maximum of three). The diagnoses should be listed in order of likelihood, most likely to least likely. Examinees should also indicate the pertinent positive and negative findings obtained from the history and physical examination to support each potential diagnosis.
To clarify previous language about USMLE expectations for examinees completing the patient note: while it is acknowledged that it is important for a physician to be able to recognize the findings that rule out certain diagnoses, the task for Step 2 CS examinees at this time is to record only the most likely diagnoses along with findings (positive and negative), that support them.
Additional information about the Step 2 CS examination, and about all USMLE examinations, is available in the USMLE Bulletin of Information.