I need the expertise from some of you on documentation guidelines in order to append the AS modifier. I would like to get multiple responses if possible. According to the Medicare guidelines, the primary surgeon's documentation for his assistant surgeon must meet medical necessity. This particular surgeon uses a nurse practitioner as his assistant. The verbage he documents in his report states that the nurse practitioner participated in the entire operation. He also states that he or she participated in prepping, draping, wound retraction, closure, and post operative management. From my past experience, this is too generalized in order to meet medical necessity. I know that Medicare guidelines says that the surgeon's documentation must give a substantial reason as to why an assistant had to be used. I have seen Medicare auditor's in the past say this is not the correct documentation for assistants to meet medical necessity. I need some feedback on this situation.