Review of Systems from file
You can always take the review of systems and the past medical/family/social history from the patient chart. BUT you do need to reference where you got the information, AND the fact that you reviewed it.
That being said ... for a subsequent hospital visit you only need two of the three elements. Your exam and MDM may be enough to give you your level of care without counting history at all.
Again ... I need to know the chief complaint to fully answer your question. But for illustration purposes, I will assume that the patient is hospitalized for elevated calcium level, so that's my chief complaint.
So for HPI you have context (found on b/w), severity (level was 13.1), modifying factor (treated with aredia) and associated signs (ext weakness).
You can then count for ROS: GI (colon cancer), Resp (lung metastases), Neuro (seizure disorder) (2-9 ROS)
For Past Med Hx you have a course of brain radiation. (For a subsequent hospital visit you only need an "interval pertinent" PMFSH)
So you have a Detailed History ... if you have a Detailed Exam OR High Complex MDM you have a 99233.
Hope that helps explain the process.
F Tessa Bartels, CPC, CEMC