CPT codes are codes that explain what the physician did. If you miss match a diagnosis to the wrong CPT it will be denied. Example: 58150 is a total abdominal hysterectomy. If you pared N39.0, bladder infection ICD-10 it would get denied. Bladder infection is not a reason to do a hysterectomy. The same with lab tests, you must match the test to a symptom or disease that code is looking for. Example: you would not do an A1C for any other diagnosis than a diabetes. Modifiers over ride denials or at least attempt to. Example: If you bill a procedure than has global days you cannot bill an office visit again until those global days are up. UNLESS the visit was for another reason other than what the surgery was done. If there is another reason for the visit than you can add a modifier 24 to the OV and try to get paid. Schooling and experience is the only way to do this and be good at it.