The guidelines say the CC can be a 'symptom, problem, condition, diagnosis, physician recommended return, or other factor that is the reason for the encounter.' So in your case the provider should state what chronic conditions they are following that require monthly medical review. For example, 'required monthly follow-up of diabetes and CHF'. I think 'medical review' alone is not quite sufficient, but if the patient has a specific condition requires periodic follow-up, that does support medical necessity.